LCOV - code coverage report
Current view: top level - src - ec_orth_solver.F (source / functions) Hit Total Coverage
Test: CP2K Regtests (git:34ef472) Lines: 482 514 93.8 %
Date: 2024-04-26 08:30:29 Functions: 9 9 100.0 %

          Line data    Source code
       1             : !--------------------------------------------------------------------------------------------------!
       2             : !   CP2K: A general program to perform molecular dynamics simulations                              !
       3             : !   Copyright 2000-2024 CP2K developers group <https://cp2k.org>                                   !
       4             : !                                                                                                  !
       5             : !   SPDX-License-Identifier: GPL-2.0-or-later                                                      !
       6             : !--------------------------------------------------------------------------------------------------!
       7             : 
       8             : ! **************************************************************************************************
       9             : !> \brief AO-based conjugate-gradient response solver routines
      10             : !>
      11             : !>
      12             : !> \date 09.2019
      13             : !> \author Fabian Belleflamme
      14             : ! **************************************************************************************************
      15             : MODULE ec_orth_solver
      16             :    USE admm_types,                      ONLY: admm_type,&
      17             :                                               get_admm_env
      18             :    USE cp_control_types,                ONLY: dft_control_type
      19             :    USE cp_dbcsr_operations,             ONLY: dbcsr_allocate_matrix_set,&
      20             :                                               dbcsr_deallocate_matrix_set
      21             :    USE cp_external_control,             ONLY: external_control
      22             :    USE dbcsr_api,                       ONLY: &
      23             :         dbcsr_add, dbcsr_add_on_diag, dbcsr_checksum, dbcsr_copy, dbcsr_create, &
      24             :         dbcsr_desymmetrize, dbcsr_dot, dbcsr_filter, dbcsr_finalize, dbcsr_get_info, &
      25             :         dbcsr_multiply, dbcsr_p_type, dbcsr_release, dbcsr_scale, dbcsr_set, dbcsr_transposed, &
      26             :         dbcsr_type, dbcsr_type_no_symmetry
      27             :    USE ec_methods,                      ONLY: create_kernel
      28             :    USE input_constants,                 ONLY: do_admm_aux_exch_func_none,&
      29             :                                               kg_tnadd_embed,&
      30             :                                               kg_tnadd_embed_ri,&
      31             :                                               ls_s_sqrt_ns,&
      32             :                                               ls_s_sqrt_proot,&
      33             :                                               precond_mlp
      34             :    USE input_section_types,             ONLY: section_vals_get_subs_vals,&
      35             :                                               section_vals_type,&
      36             :                                               section_vals_val_get
      37             :    USE iterate_matrix,                  ONLY: matrix_sqrt_Newton_Schulz,&
      38             :                                               matrix_sqrt_proot
      39             :    USE kg_correction,                   ONLY: kg_ekin_subset
      40             :    USE kinds,                           ONLY: dp
      41             :    USE machine,                         ONLY: m_flush,&
      42             :                                               m_walltime
      43             :    USE mathlib,                         ONLY: abnormal_value
      44             :    USE message_passing,                 ONLY: mp_para_env_type
      45             :    USE pw_env_types,                    ONLY: pw_env_get,&
      46             :                                               pw_env_type
      47             :    USE pw_methods,                      ONLY: pw_axpy,&
      48             :                                               pw_scale,&
      49             :                                               pw_transfer,&
      50             :                                               pw_zero
      51             :    USE pw_poisson_methods,              ONLY: pw_poisson_solve
      52             :    USE pw_poisson_types,                ONLY: pw_poisson_type
      53             :    USE pw_pool_types,                   ONLY: pw_pool_p_type,&
      54             :                                               pw_pool_type
      55             :    USE pw_types,                        ONLY: pw_c1d_gs_type,&
      56             :                                               pw_r3d_rs_type
      57             :    USE qs_environment_types,            ONLY: get_qs_env,&
      58             :                                               qs_environment_type
      59             :    USE qs_integrate_potential,          ONLY: integrate_v_rspace
      60             :    USE qs_kpp1_env_types,               ONLY: qs_kpp1_env_type
      61             :    USE qs_linres_kernel,                ONLY: apply_hfx,&
      62             :                                               apply_xc_admm
      63             :    USE qs_linres_types,                 ONLY: linres_control_type
      64             :    USE qs_p_env_methods,                ONLY: p_env_check_i_alloc,&
      65             :                                               p_env_finish_kpp1,&
      66             :                                               p_env_update_rho
      67             :    USE qs_p_env_types,                  ONLY: qs_p_env_type
      68             :    USE qs_rho_types,                    ONLY: qs_rho_get,&
      69             :                                               qs_rho_type
      70             :    USE xc,                              ONLY: xc_prep_2nd_deriv
      71             : #include "./base/base_uses.f90"
      72             : 
      73             :    IMPLICIT NONE
      74             : 
      75             :    PRIVATE
      76             : 
      77             :    ! Global parameters
      78             : 
      79             :    CHARACTER(len=*), PARAMETER, PRIVATE :: moduleN = 'ec_orth_solver'
      80             : 
      81             :    ! Public subroutines
      82             : 
      83             :    PUBLIC :: ec_response_ao
      84             : 
      85             : CONTAINS
      86             : 
      87             : ! **************************************************************************************************
      88             : !> \brief      Preconditioning of the AO-based CG linear response solver
      89             : !>             M * z_0 = r_0
      90             : !>             M(X) = [F,B], with B = [X,P]
      91             : !>             for M we need F and P in ortho basis
      92             : !>             Returns z_0, the preconditioned residual in orthonormal basis
      93             : !>
      94             : !>             All matrices are in orthonormal Lowdin basis
      95             : !>
      96             : !> \param qs_env ...
      97             : !> \param matrix_ks Ground-state Kohn-Sham matrix
      98             : !> \param matrix_p  Ground-state Density matrix
      99             : !> \param matrix_rhs Unpreconditioned residual of linear response CG
     100             : !> \param matrix_cg_z Preconditioned residual
     101             : !> \param eps_filter ...
     102             : !> \param iounit ...
     103             : !>
     104             : !> \date    01.2020
     105             : !> \author  Fabian Belleflamme
     106             : ! **************************************************************************************************
     107         572 :    SUBROUTINE preconditioner(qs_env, matrix_ks, matrix_p, matrix_rhs, &
     108             :                              matrix_cg_z, eps_filter, iounit)
     109             : 
     110             :       TYPE(qs_environment_type), POINTER                 :: qs_env
     111             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(IN), &
     112             :          POINTER                                         :: matrix_ks, matrix_p, matrix_rhs
     113             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(INOUT), &
     114             :          POINTER                                         :: matrix_cg_z
     115             :       REAL(KIND=dp), INTENT(IN)                          :: eps_filter
     116             :       INTEGER, INTENT(IN)                                :: iounit
     117             : 
     118             :       CHARACTER(len=*), PARAMETER                        :: routineN = 'preconditioner'
     119             : 
     120             :       INTEGER                                            :: handle, i, ispin, max_iter, nao, nspins
     121             :       LOGICAL                                            :: converged
     122             :       REAL(KIND=dp)                                      :: norm_res, t1, t2
     123         572 :       REAL(KIND=dp), DIMENSION(:), POINTER               :: alpha, beta, new_norm, norm_cA, norm_rr
     124         572 :       TYPE(dbcsr_p_type), DIMENSION(:), POINTER          :: matrix_Ax, matrix_b, matrix_cg, &
     125         572 :                                                             matrix_res
     126             :       TYPE(dft_control_type), POINTER                    :: dft_control
     127             :       TYPE(linres_control_type), POINTER                 :: linres_control
     128             : 
     129         572 :       CALL timeset(routineN, handle)
     130             : 
     131         572 :       CPASSERT(ASSOCIATED(qs_env))
     132         572 :       CPASSERT(ASSOCIATED(matrix_ks))
     133         572 :       CPASSERT(ASSOCIATED(matrix_p))
     134         572 :       CPASSERT(ASSOCIATED(matrix_rhs))
     135         572 :       CPASSERT(ASSOCIATED(matrix_cg_z))
     136             : 
     137         572 :       NULLIFY (dft_control, linres_control)
     138             : 
     139         572 :       t1 = m_walltime()
     140             : 
     141             :       CALL get_qs_env(qs_env=qs_env, &
     142             :                       dft_control=dft_control, &
     143         572 :                       linres_control=linres_control)
     144         572 :       nspins = dft_control%nspins
     145         572 :       CALL dbcsr_get_info(matrix_ks(1)%matrix, nfullrows_total=nao)
     146             : 
     147        6292 :       ALLOCATE (alpha(nspins), beta(nspins), new_norm(nspins), norm_cA(nspins), norm_rr(nspins))
     148             : 
     149             :       !----------------------------------------
     150             :       ! Create non-symmetric matrices: Ax, B, cg, res
     151             :       !----------------------------------------
     152             : 
     153         572 :       NULLIFY (matrix_Ax, matrix_b, matrix_cg, matrix_res)
     154         572 :       CALL dbcsr_allocate_matrix_set(matrix_Ax, nspins)
     155         572 :       CALL dbcsr_allocate_matrix_set(matrix_b, nspins)
     156         572 :       CALL dbcsr_allocate_matrix_set(matrix_cg, nspins)
     157         572 :       CALL dbcsr_allocate_matrix_set(matrix_res, nspins)
     158             : 
     159        1144 :       DO ispin = 1, nspins
     160         572 :          ALLOCATE (matrix_Ax(ispin)%matrix)
     161         572 :          ALLOCATE (matrix_b(ispin)%matrix)
     162         572 :          ALLOCATE (matrix_cg(ispin)%matrix)
     163         572 :          ALLOCATE (matrix_res(ispin)%matrix)
     164             :          CALL dbcsr_create(matrix_Ax(ispin)%matrix, name="linop MATRIX", &
     165             :                            template=matrix_ks(1)%matrix, &
     166         572 :                            matrix_type=dbcsr_type_no_symmetry)
     167             :          CALL dbcsr_create(matrix_b(ispin)%matrix, name="MATRIX B", &
     168             :                            template=matrix_ks(1)%matrix, &
     169         572 :                            matrix_type=dbcsr_type_no_symmetry)
     170             :          CALL dbcsr_create(matrix_cg(ispin)%matrix, name="TRIAL MATRIX", &
     171             :                            template=matrix_ks(1)%matrix, &
     172         572 :                            matrix_type=dbcsr_type_no_symmetry)
     173             :          CALL dbcsr_create(matrix_res(ispin)%matrix, name="RESIDUE", &
     174             :                            template=matrix_ks(1)%matrix, &
     175        1144 :                            matrix_type=dbcsr_type_no_symmetry)
     176             :       END DO
     177             : 
     178             :       !----------------------------------------
     179             :       ! Get righ-hand-side operators
     180             :       !----------------------------------------
     181             : 
     182             :       ! Initial guess z_0
     183        1144 :       DO ispin = 1, nspins
     184         572 :          CALL dbcsr_copy(matrix_cg_z(ispin)%matrix, matrix_rhs(ispin)%matrix)
     185             : 
     186             :          ! r_0 = b
     187        1144 :          CALL dbcsr_copy(matrix_res(ispin)%matrix, matrix_rhs(ispin)%matrix)
     188             :       END DO
     189             : 
     190             :       ! Projector on trial matrix
     191             :       ! Projector does not need to be applied here,
     192             :       ! as matrix_rhs already had this done before entering preconditioner
     193             :       !CALL projector(qs_env, matrix_p, matrix_cg_z, eps_filter)
     194             : 
     195             :       ! Mz_0
     196         572 :       CALL hessian_op1(matrix_ks, matrix_p, matrix_cg_z, matrix_b, matrix_Ax, eps_filter)
     197             : 
     198             :       ! r_0 = b - Ax_0
     199        1144 :       DO ispin = 1, nspins
     200        1144 :          CALL dbcsr_add(matrix_res(ispin)%matrix, matrix_Ax(ispin)%matrix, 1.0_dp, -1.0_dp)
     201             :       END DO
     202             : 
     203             :       ! Matrix projector T
     204         572 :       CALL projector(qs_env, matrix_p, matrix_res, eps_filter)
     205             : 
     206        1144 :       DO ispin = 1, nspins
     207             :          ! cg = p_0 = z_0
     208        1144 :          CALL dbcsr_copy(matrix_cg(ispin)%matrix, matrix_res(ispin)%matrix)
     209             :       END DO
     210             : 
     211             :       ! header
     212         572 :       IF (iounit > 0) THEN
     213         286 :          WRITE (iounit, "(/,T10,A)") "Preconditioning of search direction"
     214             :          WRITE (iounit, "(/,T10,A,T25,A,T42,A,T62,A,/,T10,A)") &
     215         286 :             "Iteration", "Stepsize", "Convergence", "Time", &
     216         572 :             REPEAT("-", 58)
     217             :       END IF
     218             : 
     219        1144 :       alpha(:) = 0.0_dp
     220         572 :       max_iter = 200
     221         572 :       converged = .FALSE.
     222         572 :       norm_res = 0.0_dp
     223             : 
     224             :       ! start iteration
     225        3062 :       iteration: DO i = 1, max_iter
     226             : 
     227             :          ! Hessian Ax = [F,B] is updated preconditioner
     228        3062 :          CALL hessian_op1(matrix_ks, matrix_p, matrix_cg, matrix_b, matrix_Ax, eps_filter)
     229             : 
     230             :          ! Matrix projector
     231        3062 :          CALL projector(qs_env, matrix_p, matrix_Ax, eps_filter)
     232             : 
     233        6124 :          DO ispin = 1, nspins
     234             : 
     235             :             ! Tr(r_0 * r_0)
     236        3062 :             CALL dbcsr_dot(matrix_res(ispin)%matrix, matrix_res(ispin)%matrix, norm_rr(ispin))
     237        3062 :             IF (abnormal_value(norm_rr(ispin))) &
     238           0 :                CPABORT("Preconditioner: Tr[r_j*r_j] is an abnormal value (NaN/Inf)")
     239             : 
     240        3062 :             IF (norm_rr(ispin) .LT. 0.0_dp) CPABORT("norm_rr < 0")
     241        3062 :             norm_res = MAX(norm_res, ABS(norm_rr(ispin)/REAL(nao, dp)))
     242             : 
     243             :             ! norm_cA = tr(Ap_j * p_j)
     244        3062 :             CALL dbcsr_dot(matrix_cg(ispin)%matrix, matrix_Ax(ispin)%matrix, norm_cA(ispin))
     245             : 
     246             :             ! Determine step-size
     247        3062 :             IF (norm_cA(ispin) .LT. linres_control%eps) THEN
     248          30 :                alpha(ispin) = 1.0_dp
     249             :             ELSE
     250        3032 :                alpha(ispin) = norm_rr(ispin)/norm_cA(ispin)
     251             :             END IF
     252             : 
     253             :             ! x_j+1 = x_j + alpha*p_j
     254             :             ! save contribution of this iteration
     255        3062 :             CALL dbcsr_add(matrix_cg_z(ispin)%matrix, matrix_cg(ispin)%matrix, 1.0_dp, alpha(ispin))
     256             : 
     257             :             ! r_j+1 = r_j - alpha * Ap_j
     258        6124 :             CALL dbcsr_add(matrix_res(ispin)%matrix, matrix_Ax(ispin)%matrix, 1.0_dp, -alpha(ispin))
     259             : 
     260             :          END DO
     261             : 
     262        3062 :          norm_res = 0.0_dp
     263             : 
     264        6124 :          DO ispin = 1, nspins
     265             :             ! Tr[r_j+1*z_j+1]
     266        3062 :             CALL dbcsr_dot(matrix_res(ispin)%matrix, matrix_res(ispin)%matrix, new_norm(ispin))
     267        3062 :             IF (new_norm(ispin) .LT. 0.0_dp) CPABORT("tr(r_j+1*z_j+1) < 0")
     268        3062 :             IF (abnormal_value(new_norm(ispin))) &
     269           0 :                CPABORT("Preconditioner: Tr[r_j+1*z_j+1] is an abnormal value (NaN/Inf)")
     270        3062 :             norm_res = MAX(norm_res, new_norm(ispin)/REAL(nao, dp))
     271             : 
     272             :             IF (norm_rr(ispin) .LT. linres_control%eps*0.001_dp &
     273        3062 :                 .OR. new_norm(ispin) .LT. linres_control%eps*0.001_dp) THEN
     274          36 :                beta(ispin) = 0.0_dp
     275          36 :                converged = .TRUE.
     276             :             ELSE
     277        3026 :                beta(ispin) = new_norm(ispin)/norm_rr(ispin)
     278             :             END IF
     279             : 
     280             :             ! update new search vector (matrix cg)
     281             :             ! cg_j+1 = z_j+1 + beta*cg_j
     282        3062 :             CALL dbcsr_add(matrix_cg(ispin)%matrix, matrix_res(ispin)%matrix, beta(ispin), 1.0_dp)
     283        3062 :             CALL dbcsr_filter(matrix_cg(ispin)%matrix, eps_filter)
     284             : 
     285        6124 :             norm_rr(ispin) = new_norm(ispin)
     286             :          END DO
     287             : 
     288             :          ! Convergence criteria
     289        3062 :          IF (norm_res .LT. linres_control%eps) THEN
     290         572 :             converged = .TRUE.
     291             :          END IF
     292             : 
     293        3062 :          t2 = m_walltime()
     294             :          IF (i .EQ. 1 .OR. MOD(i, 1) .EQ. 0 .OR. converged) THEN
     295        3062 :             IF (iounit > 0) THEN
     296             :                WRITE (iounit, "(T10,I5,T25,1E8.2,T33,F25.14,T58,F8.2)") &
     297        4593 :                   i, MAXVAL(alpha), norm_res, t2 - t1
     298             :                ! Convergence in scientific notation
     299             :                !WRITE (iounit, "(T10,I5,T25,1E8.2,T42,1E14.8,T58,F8.2)") &
     300             :                !   i, MAXVAL(alpha), norm_res, t2 - t1
     301        1531 :                CALL m_flush(iounit)
     302             :             END IF
     303             :          END IF
     304        3062 :          IF (converged) THEN
     305         572 :             IF (iounit > 0) THEN
     306         286 :                WRITE (iounit, "(/,T10,A,I4,A,/)") "The precon solver converged in ", i, " iterations."
     307         286 :                CALL m_flush(iounit)
     308             :             END IF
     309             :             EXIT iteration
     310             :          END IF
     311             : 
     312             :          ! Max number of iteration reached
     313        2490 :          IF (i == max_iter) THEN
     314           0 :             IF (iounit > 0) THEN
     315             :                WRITE (iounit, "(/,T10,A/)") &
     316           0 :                   "The precon solver didnt converge! Maximum number of iterations reached."
     317           0 :                CALL m_flush(iounit)
     318             :             END IF
     319             :             converged = .FALSE.
     320             :          END IF
     321             : 
     322             :       END DO iteration
     323             : 
     324             :       ! Matrix projector
     325         572 :       CALL projector(qs_env, matrix_p, matrix_cg_z, eps_filter)
     326             : 
     327             :       ! Release matrices
     328         572 :       CALL dbcsr_deallocate_matrix_set(matrix_Ax)
     329         572 :       CALL dbcsr_deallocate_matrix_set(matrix_b)
     330         572 :       CALL dbcsr_deallocate_matrix_set(matrix_res)
     331         572 :       CALL dbcsr_deallocate_matrix_set(matrix_cg)
     332             : 
     333         572 :       DEALLOCATE (alpha, beta, new_norm, norm_cA, norm_rr)
     334             : 
     335         572 :       CALL timestop(handle)
     336             : 
     337        1144 :    END SUBROUTINE preconditioner
     338             : 
     339             : ! **************************************************************************************************
     340             : !> \brief AO-based conjugate gradient linear response solver.
     341             : !>        In goes the right hand side B of the equation AZ=B, and the linear transformation of the
     342             : !>        Hessian matrix A on trial matrices is iteratively solved. Result are
     343             : !>        the response density matrix_pz, and the energy-weighted response density matrix_wz.
     344             : !>
     345             : !> \param qs_env ...
     346             : !> \param p_env ...
     347             : !> \param matrix_hz Right hand-side of linear response equation
     348             : !> \param matrix_pz Response density
     349             : !> \param matrix_wz Energy-weighted response density matrix
     350             : !> \param iounit ...
     351             : !> \param should_stop ...
     352             : !>
     353             : !> \date    01.2020
     354             : !> \author  Fabian Belleflamme
     355             : ! **************************************************************************************************
     356         132 :    SUBROUTINE ec_response_ao(qs_env, p_env, matrix_hz, matrix_pz, matrix_wz, iounit, should_stop)
     357             : 
     358             :       TYPE(qs_environment_type), POINTER                 :: qs_env
     359             :       TYPE(qs_p_env_type), POINTER                       :: p_env
     360             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(IN), &
     361             :          POINTER                                         :: matrix_hz
     362             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(INOUT), &
     363             :          POINTER                                         :: matrix_pz, matrix_wz
     364             :       INTEGER, INTENT(IN)                                :: iounit
     365             :       LOGICAL, INTENT(OUT)                               :: should_stop
     366             : 
     367             :       CHARACTER(len=*), PARAMETER                        :: routineN = 'ec_response_ao'
     368             : 
     369             :       INTEGER                                            :: handle, i, ispin, max_iter_lanczos, nao, &
     370             :                                                             nspins, s_sqrt_method, s_sqrt_order
     371             :       LOGICAL                                            :: restart
     372             :       REAL(KIND=dp)                                      :: eps_filter, eps_lanczos, focc, &
     373             :                                                             min_shift, norm_res, old_conv, shift, &
     374             :                                                             t1, t2
     375         132 :       REAL(KIND=dp), DIMENSION(:), POINTER               :: alpha, beta, new_norm, norm_cA, norm_rr, &
     376         132 :                                                             tr_rz00
     377         132 :       TYPE(dbcsr_p_type), DIMENSION(:), POINTER :: ksmat, matrix_Ax, matrix_cg, matrix_cg_z, &
     378         132 :          matrix_ks, matrix_nsc, matrix_p, matrix_res, matrix_s, matrix_z, matrix_z0, rho_ao
     379             :       TYPE(dbcsr_type)                                   :: matrix_s_sqrt, matrix_s_sqrt_inv, &
     380             :                                                             matrix_tmp
     381             :       TYPE(dft_control_type), POINTER                    :: dft_control
     382             :       TYPE(linres_control_type), POINTER                 :: linres_control
     383             :       TYPE(qs_rho_type), POINTER                         :: rho
     384             :       TYPE(section_vals_type), POINTER                   :: solver_section
     385             : 
     386         132 :       CALL timeset(routineN, handle)
     387             : 
     388         132 :       CPASSERT(ASSOCIATED(qs_env))
     389         132 :       CPASSERT(ASSOCIATED(matrix_hz))
     390         132 :       CPASSERT(ASSOCIATED(matrix_pz))
     391         132 :       CPASSERT(ASSOCIATED(matrix_wz))
     392             : 
     393         132 :       NULLIFY (dft_control, ksmat, matrix_s, linres_control, rho)
     394             : 
     395         132 :       t1 = m_walltime()
     396             : 
     397             :       CALL get_qs_env(qs_env=qs_env, &
     398             :                       dft_control=dft_control, &
     399             :                       linres_control=linres_control, &
     400             :                       matrix_ks=ksmat, &
     401             :                       matrix_s=matrix_s, &
     402         132 :                       rho=rho)
     403         132 :       nspins = dft_control%nspins
     404             : 
     405         132 :       CALL dbcsr_get_info(matrix_s(1)%matrix, nfullrows_total=nao)
     406             : 
     407         132 :       solver_section => section_vals_get_subs_vals(qs_env%input, "DFT%ENERGY_CORRECTION%RESPONSE_SOLVER")
     408         132 :       CALL section_vals_val_get(solver_section, "S_SQRT_METHOD", i_val=s_sqrt_method)
     409         132 :       CALL section_vals_val_get(solver_section, "S_SQRT_ORDER", i_val=s_sqrt_order)
     410         132 :       CALL section_vals_val_get(solver_section, "EPS_LANCZOS", r_val=eps_lanczos)
     411         132 :       CALL section_vals_val_get(solver_section, "MAX_ITER_LANCZOS", i_val=max_iter_lanczos)
     412             : 
     413         132 :       eps_filter = linres_control%eps_filter
     414             : 
     415         132 :       CALL qs_rho_get(rho, rho_ao=rho_ao)
     416             : 
     417        1452 :       ALLOCATE (alpha(nspins), beta(nspins), new_norm(nspins), norm_cA(nspins), norm_rr(nspins))
     418         396 :       ALLOCATE (tr_rz00(nspins))
     419             : 
     420             :       ! local matrix P, KS, and NSC
     421             :       ! to bring into orthogonal basis
     422         132 :       NULLIFY (matrix_p, matrix_ks, matrix_nsc)
     423         132 :       CALL dbcsr_allocate_matrix_set(matrix_p, nspins)
     424         132 :       CALL dbcsr_allocate_matrix_set(matrix_ks, nspins)
     425         132 :       CALL dbcsr_allocate_matrix_set(matrix_nsc, nspins)
     426         264 :       DO ispin = 1, nspins
     427         132 :          ALLOCATE (matrix_p(ispin)%matrix)
     428         132 :          ALLOCATE (matrix_ks(ispin)%matrix)
     429         132 :          ALLOCATE (matrix_nsc(ispin)%matrix)
     430             :          CALL dbcsr_create(matrix_p(ispin)%matrix, name="P_IN ORTHO", &
     431             :                            template=ksmat(1)%matrix, &
     432         132 :                            matrix_type=dbcsr_type_no_symmetry)
     433             :          CALL dbcsr_create(matrix_ks(ispin)%matrix, name="KS_IN ORTHO", &
     434             :                            template=ksmat(1)%matrix, &
     435         132 :                            matrix_type=dbcsr_type_no_symmetry)
     436             :          CALL dbcsr_create(matrix_nsc(ispin)%matrix, name="NSC IN ORTHO", &
     437             :                            template=ksmat(1)%matrix, &
     438         132 :                            matrix_type=dbcsr_type_no_symmetry)
     439             : 
     440         132 :          CALL dbcsr_desymmetrize(rho_ao(ispin)%matrix, matrix_p(ispin)%matrix)
     441         132 :          CALL dbcsr_desymmetrize(ksmat(ispin)%matrix, matrix_ks(ispin)%matrix)
     442         264 :          CALL dbcsr_desymmetrize(matrix_hz(ispin)%matrix, matrix_nsc(ispin)%matrix)
     443             :       END DO
     444             : 
     445             :       ! Scale matrix_p by factor 1/2 in closed-shell
     446         132 :       IF (nspins == 1) CALL dbcsr_scale(matrix_p(1)%matrix, 0.5_dp)
     447             : 
     448             :       ! Transform P, KS, and Harris kernel matrix into Orthonormal basis
     449             :       CALL dbcsr_create(matrix_s_sqrt, template=matrix_s(1)%matrix, &
     450         132 :                         matrix_type=dbcsr_type_no_symmetry)
     451             :       CALL dbcsr_create(matrix_s_sqrt_inv, template=matrix_s(1)%matrix, &
     452         132 :                         matrix_type=dbcsr_type_no_symmetry)
     453             : 
     454           0 :       SELECT CASE (s_sqrt_method)
     455             :       CASE (ls_s_sqrt_proot)
     456             :          CALL matrix_sqrt_proot(matrix_s_sqrt, matrix_s_sqrt_inv, &
     457             :                                 matrix_s(1)%matrix, eps_filter, &
     458           0 :                                 s_sqrt_order, eps_lanczos, max_iter_lanczos, symmetrize=.TRUE.)
     459             :       CASE (ls_s_sqrt_ns)
     460             :          CALL matrix_sqrt_Newton_Schulz(matrix_s_sqrt, matrix_s_sqrt_inv, &
     461             :                                         matrix_s(1)%matrix, eps_filter, &
     462         132 :                                         s_sqrt_order, eps_lanczos, max_iter_lanczos)
     463             :       CASE DEFAULT
     464         132 :          CPABORT("Unknown sqrt method.")
     465             :       END SELECT
     466             : 
     467             :       ! Transform into orthonormal Lowdin basis
     468         264 :       DO ispin = 1, nspins
     469         132 :          CALL transform_m_orth(matrix_p(ispin)%matrix, matrix_s_sqrt, eps_filter)
     470         132 :          CALL transform_m_orth(matrix_ks(ispin)%matrix, matrix_s_sqrt_inv, eps_filter)
     471         264 :          CALL transform_m_orth(matrix_nsc(ispin)%matrix, matrix_s_sqrt_inv, eps_filter)
     472             :       END DO
     473             : 
     474             :       !----------------------------------------
     475             :       ! Create non-symmetric work matrices: Ax, cg, res
     476             :       ! Content of Ax, cg, cg_z, res, z0 anti-symmetric
     477             :       ! Content of z symmetric
     478             :       !----------------------------------------
     479             : 
     480         132 :       CALL dbcsr_create(matrix_tmp, template=matrix_s(1)%matrix, matrix_type=dbcsr_type_no_symmetry)
     481             : 
     482         132 :       NULLIFY (matrix_Ax, matrix_cg, matrix_cg_z, matrix_res, matrix_z, matrix_z0)
     483         132 :       CALL dbcsr_allocate_matrix_set(matrix_Ax, nspins)
     484         132 :       CALL dbcsr_allocate_matrix_set(matrix_cg, nspins)
     485         132 :       CALL dbcsr_allocate_matrix_set(matrix_cg_z, nspins)
     486         132 :       CALL dbcsr_allocate_matrix_set(matrix_res, nspins)
     487         132 :       CALL dbcsr_allocate_matrix_set(matrix_z, nspins)
     488         132 :       CALL dbcsr_allocate_matrix_set(matrix_z0, nspins)
     489             : 
     490         264 :       DO ispin = 1, nspins
     491         132 :          ALLOCATE (matrix_Ax(ispin)%matrix)
     492         132 :          ALLOCATE (matrix_cg(ispin)%matrix)
     493         132 :          ALLOCATE (matrix_cg_z(ispin)%matrix)
     494         132 :          ALLOCATE (matrix_res(ispin)%matrix)
     495         132 :          ALLOCATE (matrix_z(ispin)%matrix)
     496         132 :          ALLOCATE (matrix_z0(ispin)%matrix)
     497             :          CALL dbcsr_create(matrix_Ax(ispin)%matrix, name="linop MATRIX", &
     498             :                            template=matrix_s(1)%matrix, &
     499         132 :                            matrix_type=dbcsr_type_no_symmetry)
     500             :          CALL dbcsr_create(matrix_cg(ispin)%matrix, name="TRIAL MATRIX", &
     501             :                            template=matrix_s(1)%matrix, &
     502         132 :                            matrix_type=dbcsr_type_no_symmetry)
     503             :          CALL dbcsr_create(matrix_cg_z(ispin)%matrix, name="MATRIX CG-Z", &
     504             :                            template=matrix_s(1)%matrix, &
     505         132 :                            matrix_type=dbcsr_type_no_symmetry)
     506             :          CALL dbcsr_create(matrix_res(ispin)%matrix, name="RESIDUE", &
     507             :                            template=matrix_s(1)%matrix, &
     508         132 :                            matrix_type=dbcsr_type_no_symmetry)
     509             :          CALL dbcsr_create(matrix_z(ispin)%matrix, name="Z-Matrix", &
     510             :                            template=matrix_s(1)%matrix, &
     511         132 :                            matrix_type=dbcsr_type_no_symmetry)
     512             :          CALL dbcsr_create(matrix_z0(ispin)%matrix, name="p after precondi-Matrix", &
     513             :                            template=matrix_s(1)%matrix, &
     514         264 :                            matrix_type=dbcsr_type_no_symmetry)
     515             :       END DO
     516             : 
     517             :       !----------------------------------------
     518             :       ! Get righ-hand-side operators
     519             :       !----------------------------------------
     520             : 
     521             :       ! Spin factor
     522         132 :       focc = -2.0_dp
     523         132 :       IF (nspins == 1) focc = -4.0_dp
     524             : 
     525             :       ! E^[1]_Harris = -4*G[\delta P]*Pin - Pin*G[\delta P] = -4*[G[\delta P], Pin]
     526         132 :       CALL commutator(matrix_nsc, matrix_p, matrix_res, eps_filter, .FALSE., alpha=focc)
     527             : 
     528             :       ! Initial guess cg_Z
     529         264 :       DO ispin = 1, nspins
     530         264 :          CALL dbcsr_copy(matrix_cg_z(ispin)%matrix, matrix_res(ispin)%matrix)
     531             :       END DO
     532             : 
     533             :       ! Projector on trial matrix
     534         132 :       CALL projector(qs_env, matrix_p, matrix_cg_z, eps_filter)
     535             : 
     536             :       ! Ax0
     537             :       CALL build_hessian_op(qs_env=qs_env, &
     538             :                             p_env=p_env, &
     539             :                             matrix_ks=matrix_ks, &
     540             :                             matrix_p=matrix_p, &   ! p
     541             :                             matrix_s_sqrt_inv=matrix_s_sqrt_inv, &
     542             :                             matrix_cg=matrix_cg_z, & ! cg
     543             :                             matrix_Ax=matrix_Ax, &
     544         132 :                             eps_filter=eps_filter)
     545             : 
     546             :       ! r_0 = b - Ax0
     547         264 :       DO ispin = 1, nspins
     548         264 :          CALL dbcsr_add(matrix_res(ispin)%matrix, matrix_Ax(ispin)%matrix, 1.0_dp, -1.0_dp)
     549             :       END DO
     550             : 
     551             :       ! Matrix projector T
     552         132 :       CALL projector(qs_env, matrix_p, matrix_res, eps_filter)
     553             : 
     554             :       ! Preconditioner
     555         132 :       linres_control%flag = ""
     556         132 :       IF (linres_control%preconditioner_type == precond_mlp) THEN
     557             :          ! M * z_0 = r_0
     558             :          ! Conjugate gradient returns z_0
     559             :          CALL preconditioner(qs_env=qs_env, &
     560             :                              matrix_ks=matrix_ks, &
     561             :                              matrix_p=matrix_p, &
     562             :                              matrix_rhs=matrix_res, &
     563             :                              matrix_cg_z=matrix_z0, &
     564             :                              eps_filter=eps_filter, &
     565         130 :                              iounit=iounit)
     566         130 :          linres_control%flag = "PCG-AO"
     567             :       ELSE
     568             :          ! z_0 = r_0
     569           4 :          DO ispin = 1, nspins
     570           2 :             CALL dbcsr_copy(matrix_z0(ispin)%matrix, matrix_res(ispin)%matrix)
     571           4 :             linres_control%flag = "CG-AO"
     572             :          END DO
     573             :       END IF
     574             : 
     575         132 :       norm_res = 0.0_dp
     576             : 
     577         264 :       DO ispin = 1, nspins
     578             :          ! cg = p_0 = z_0
     579         132 :          CALL dbcsr_copy(matrix_cg(ispin)%matrix, matrix_z0(ispin)%matrix)
     580             : 
     581             :          ! Tr(r_0 * z_0)
     582         132 :          CALL dbcsr_dot(matrix_res(ispin)%matrix, matrix_cg(ispin)%matrix, norm_rr(ispin))
     583             : 
     584         132 :          IF (norm_rr(ispin) .LT. 0.0_dp) CPABORT("norm_rr < 0")
     585         264 :          norm_res = MAX(norm_res, ABS(norm_rr(ispin)/REAL(nao, dp)))
     586             :       END DO
     587             : 
     588             :       ! eigenvalue shifting
     589         132 :       min_shift = 0.0_dp
     590         132 :       old_conv = norm_rr(1)
     591         132 :       shift = MIN(10.0_dp, MAX(min_shift, 0.05_dp*old_conv))
     592         132 :       old_conv = 100.0_dp
     593             : 
     594             :       ! header
     595         132 :       IF (iounit > 0) THEN
     596             :          WRITE (iounit, "(/,T3,A,T16,A,T25,A,T38,A,T52,A,/,T3,A)") &
     597          66 :             "Iteration", "Method", "Stepsize", "Convergence", "Time", &
     598         132 :             REPEAT("-", 80)
     599             :       END IF
     600             : 
     601         264 :       alpha(:) = 0.0_dp
     602         132 :       restart = .FALSE.
     603         132 :       should_stop = .FALSE.
     604         132 :       linres_control%converged = .FALSE.
     605             : 
     606             :       ! start iteration
     607         580 :       iteration: DO i = 1, linres_control%max_iter
     608             : 
     609             :          ! Convergence criteria
     610             :          ! default for eps 10E-6 in MO_linres
     611         534 :          IF (norm_res .LT. linres_control%eps) THEN
     612          86 :             linres_control%converged = .TRUE.
     613             :          END IF
     614             : 
     615         534 :          t2 = m_walltime()
     616             :          IF (i .EQ. 1 .OR. MOD(i, 1) .EQ. 0 .OR. linres_control%converged &
     617             :              .OR. restart .OR. should_stop) THEN
     618         534 :             IF (iounit > 0) THEN
     619             :                WRITE (iounit, "(T5,I5,T18,A3,T28,L1,T38,1E8.2,T48,F16.10,T68,F8.2)") &
     620         801 :                   i, linres_control%flag, restart, MAXVAL(alpha), norm_res, t2 - t1
     621         267 :                CALL m_flush(iounit)
     622             :             END IF
     623             :          END IF
     624         534 :          IF (linres_control%converged) THEN
     625          86 :             IF (iounit > 0) THEN
     626          43 :                WRITE (iounit, "(/,T2,A,I4,A,/)") "The linear solver converged in ", i, " iterations."
     627          43 :                CALL m_flush(iounit)
     628             :             END IF
     629             :             EXIT iteration
     630         448 :          ELSE IF (should_stop) THEN
     631           0 :             IF (iounit > 0) THEN
     632           0 :                WRITE (iounit, "(/,T2,A,I4,A,/)") "The linear solver did NOT converge! External stop"
     633           0 :                CALL m_flush(iounit)
     634             :             END IF
     635             :             EXIT iteration
     636             :          END IF
     637             : 
     638             :          ! Max number of iteration reached
     639         448 :          IF (i == linres_control%max_iter) THEN
     640          46 :             IF (iounit > 0) THEN
     641             :                WRITE (iounit, "(/,T2,A/)") &
     642          23 :                   "The linear solver didnt converge! Maximum number of iterations reached."
     643          23 :                CALL m_flush(iounit)
     644             :             END IF
     645          46 :             linres_control%converged = .FALSE.
     646             :          END IF
     647             : 
     648             :          ! Hessian Ax = [F,B] + [G(B),P]
     649             :          CALL build_hessian_op(qs_env=qs_env, &
     650             :                                p_env=p_env, &
     651             :                                matrix_ks=matrix_ks, &
     652             :                                matrix_p=matrix_p, &   ! p
     653             :                                matrix_s_sqrt_inv=matrix_s_sqrt_inv, &
     654             :                                matrix_cg=matrix_cg, & ! cg
     655             :                                matrix_Ax=matrix_Ax, &
     656         448 :                                eps_filter=eps_filter)
     657             : 
     658             :          ! Matrix projector T
     659         448 :          CALL projector(qs_env, matrix_p, matrix_Ax, eps_filter)
     660             : 
     661         896 :          DO ispin = 1, nspins
     662             : 
     663         448 :             CALL dbcsr_filter(matrix_Ax(ispin)%matrix, eps_filter)
     664             :             ! norm_cA = tr(Ap_j * p_j)
     665         448 :             CALL dbcsr_dot(matrix_cg(ispin)%matrix, matrix_Ax(ispin)%matrix, norm_cA(ispin))
     666             : 
     667         896 :             IF (norm_cA(ispin) .LT. 0.0_dp) THEN
     668             : 
     669             :                ! Recalculate w/o preconditioner
     670           0 :                IF (i > 1) THEN
     671             :                   ! p = -z + beta*p
     672             :                   CALL dbcsr_add(matrix_cg(ispin)%matrix, matrix_z0(ispin)%matrix, &
     673           0 :                                  beta(ispin), -1.0_dp)
     674           0 :                   CALL dbcsr_dot(matrix_res(ispin)%matrix, matrix_res(ispin)%matrix, new_norm(ispin))
     675           0 :                   beta(ispin) = new_norm(ispin)/tr_rz00(ispin)
     676             :                   CALL dbcsr_add(matrix_cg(ispin)%matrix, matrix_res(ispin)%matrix, &
     677           0 :                                  beta(ispin), 1.0_dp)
     678           0 :                   norm_rr(ispin) = new_norm(ispin)
     679             :                ELSE
     680           0 :                   CALL dbcsr_copy(matrix_res(ispin)%matrix, matrix_cg(ispin)%matrix)
     681           0 :                   CALL dbcsr_dot(matrix_res(ispin)%matrix, matrix_res(ispin)%matrix, norm_rr(ispin))
     682             :                END IF
     683             : 
     684             :                CALL build_hessian_op(qs_env=qs_env, &
     685             :                                      p_env=p_env, &
     686             :                                      matrix_ks=matrix_ks, &
     687             :                                      matrix_p=matrix_p, &   ! p
     688             :                                      matrix_s_sqrt_inv=matrix_s_sqrt_inv, &
     689             :                                      matrix_cg=matrix_cg, & ! cg
     690             :                                      matrix_Ax=matrix_Ax, &
     691           0 :                                      eps_filter=eps_filter)
     692             : 
     693             :                ! Matrix projector T
     694           0 :                CALL projector(qs_env, matrix_p, matrix_Ax, eps_filter)
     695             : 
     696           0 :                CALL dbcsr_dot(matrix_cg(ispin)%matrix, matrix_Ax(ispin)%matrix, norm_cA(ispin))
     697             : 
     698           0 :                CPABORT("tr(Ap_j*p_j) < 0")
     699           0 :                IF (abnormal_value(norm_cA(ispin))) &
     700           0 :                   CPABORT("Preconditioner: Tr[Ap_j*p_j] is an abnormal value (NaN/Inf)")
     701             : 
     702             :             END IF
     703             : 
     704             :          END DO
     705             : 
     706         896 :          DO ispin = 1, nspins
     707             :             ! Determine step-size
     708         448 :             IF (norm_cA(ispin) .LT. linres_control%eps) THEN
     709           0 :                alpha(ispin) = 1.0_dp
     710             :             ELSE
     711         448 :                alpha(ispin) = norm_rr(ispin)/norm_cA(ispin)
     712             :             END IF
     713             : 
     714             :             ! x_j+1 = x_j + alpha*p_j
     715             :             ! save response-denisty of this iteration
     716         896 :             CALL dbcsr_add(matrix_cg_z(ispin)%matrix, matrix_cg(ispin)%matrix, 1.0_dp, alpha(ispin))
     717             :          END DO
     718             : 
     719             :          ! need to recompute the residue
     720         448 :          restart = .FALSE.
     721         448 :          IF (MOD(i, linres_control%restart_every) .EQ. 0) THEN
     722             :             !
     723             :             ! r_j+1 = b - A * x_j+1
     724             :             CALL build_hessian_op(qs_env=qs_env, &
     725             :                                   p_env=p_env, &
     726             :                                   matrix_ks=matrix_ks, &
     727             :                                   matrix_p=matrix_p, &
     728             :                                   matrix_s_sqrt_inv=matrix_s_sqrt_inv, &
     729             :                                   matrix_cg=matrix_cg_z, & ! cg
     730             :                                   matrix_Ax=matrix_Ax, &
     731           0 :                                   eps_filter=eps_filter)
     732             :             ! b
     733           0 :             CALL commutator(matrix_nsc, matrix_p, matrix_res, eps_filter, .FALSE., alpha=focc)
     734             : 
     735           0 :             DO ispin = 1, nspins
     736           0 :                CALL dbcsr_add(matrix_res(ispin)%matrix, matrix_Ax(ispin)%matrix, 1.0_dp, -1.0_dp)
     737             :             END DO
     738             : 
     739           0 :             CALL projector(qs_env, matrix_p, matrix_res, eps_filter)
     740             :             !
     741           0 :             restart = .TRUE.
     742             :          ELSE
     743             :             ! proj Ap onto the virtual subspace
     744         448 :             CALL projector(qs_env, matrix_p, matrix_Ax, eps_filter)
     745             :             !
     746             :             ! r_j+1 = r_j - alpha * Ap_j
     747         896 :             DO ispin = 1, nspins
     748         896 :                CALL dbcsr_add(matrix_res(ispin)%matrix, matrix_Ax(ispin)%matrix, 1.0_dp, -alpha(ispin))
     749             :             END DO
     750         448 :             restart = .FALSE.
     751             :          END IF
     752             : 
     753             :          ! Preconditioner
     754         448 :          linres_control%flag = ""
     755         448 :          IF (linres_control%preconditioner_type == precond_mlp) THEN
     756             :             ! M * z_j+1 = r_j+1
     757             :             ! Conjugate gradient returns z_j+1
     758             :             CALL preconditioner(qs_env=qs_env, &
     759             :                                 matrix_ks=matrix_ks, &
     760             :                                 matrix_p=matrix_p, &
     761             :                                 matrix_rhs=matrix_res, &
     762             :                                 matrix_cg_z=matrix_z0, &
     763             :                                 eps_filter=eps_filter, &
     764         442 :                                 iounit=iounit)
     765         442 :             linres_control%flag = "PCG-AO"
     766             :          ELSE
     767          12 :             DO ispin = 1, nspins
     768          12 :                CALL dbcsr_copy(matrix_z0(ispin)%matrix, matrix_res(ispin)%matrix)
     769             :             END DO
     770           6 :             linres_control%flag = "CG-AO"
     771             :          END IF
     772             : 
     773         448 :          norm_res = 0.0_dp
     774             : 
     775         896 :          DO ispin = 1, nspins
     776             :             ! Tr[r_j+1*z_j+1]
     777         448 :             CALL dbcsr_dot(matrix_res(ispin)%matrix, matrix_z0(ispin)%matrix, new_norm(ispin))
     778         448 :             IF (new_norm(ispin) .LT. 0.0_dp) CPABORT("tr(r_j+1*z_j+1) < 0")
     779         448 :             IF (abnormal_value(new_norm(ispin))) &
     780           0 :                CPABORT("Preconditioner: Tr[r_j+1*z_j+1] is an abnormal value (NaN/Inf)")
     781         448 :             norm_res = MAX(norm_res, new_norm(ispin)/REAL(nao, dp))
     782             : 
     783         448 :             IF (norm_rr(ispin) .LT. linres_control%eps .OR. new_norm(ispin) .LT. linres_control%eps) THEN
     784          16 :                beta(ispin) = 0.0_dp
     785          16 :                linres_control%converged = .TRUE.
     786             :             ELSE
     787         432 :                beta(ispin) = new_norm(ispin)/norm_rr(ispin)
     788             :             END IF
     789             : 
     790             :             ! update new search vector (matrix cg)
     791             :             ! Here: cg_j+1 = z_j+1 + beta*cg_j
     792         448 :             CALL dbcsr_add(matrix_cg(ispin)%matrix, matrix_z0(ispin)%matrix, beta(ispin), 1.0_dp)
     793         448 :             CALL dbcsr_filter(matrix_cg(ispin)%matrix, eps_filter)
     794             : 
     795         448 :             tr_rz00(ispin) = norm_rr(ispin)
     796         896 :             norm_rr(ispin) = new_norm(ispin)
     797             :          END DO
     798             : 
     799             :          ! Can we exit the loop?
     800             :          CALL external_control(should_stop, "LS_SOLVER", target_time=qs_env%target_time, &
     801         494 :                                start_time=qs_env%start_time)
     802             : 
     803             :       END DO iteration
     804             : 
     805             :       ! Matrix projector
     806         132 :       CALL projector(qs_env, matrix_p, matrix_cg_z, eps_filter)
     807             : 
     808             :       ! Z = [cg_z,P]
     809         132 :       CALL commutator(matrix_cg_z, matrix_p, matrix_z, eps_filter, .TRUE., alpha=0.5_dp)
     810             : 
     811         264 :       DO ispin = 1, nspins
     812             :          ! Transform Z-matrix back into non-orthogonal basis
     813         132 :          CALL transform_m_orth(matrix_z(ispin)%matrix, matrix_s_sqrt_inv, eps_filter)
     814             : 
     815             :          ! Export Z-Matrix
     816         264 :          CALL dbcsr_copy(matrix_pz(ispin)%matrix, matrix_z(ispin)%matrix, keep_sparsity=.TRUE.)
     817             :       END DO
     818             : 
     819             :       ! Calculate energy-weighted response density matrix
     820             :       ! AO: Wz = 0.5*(Z*KS*P + P*KS*Z)
     821         132 :       CALL ec_wz_matrix(qs_env, matrix_pz, matrix_wz, eps_filter)
     822             : 
     823             :       ! Release matrices
     824         132 :       CALL dbcsr_release(matrix_tmp)
     825             : 
     826         132 :       CALL dbcsr_release(matrix_s_sqrt)
     827         132 :       CALL dbcsr_release(matrix_s_sqrt_inv)
     828             : 
     829         132 :       CALL dbcsr_deallocate_matrix_set(matrix_p)
     830         132 :       CALL dbcsr_deallocate_matrix_set(matrix_ks)
     831         132 :       CALL dbcsr_deallocate_matrix_set(matrix_nsc)
     832         132 :       CALL dbcsr_deallocate_matrix_set(matrix_z)
     833         132 :       CALL dbcsr_deallocate_matrix_set(matrix_Ax)
     834         132 :       CALL dbcsr_deallocate_matrix_set(matrix_res)
     835         132 :       CALL dbcsr_deallocate_matrix_set(matrix_cg)
     836         132 :       CALL dbcsr_deallocate_matrix_set(matrix_cg_z)
     837         132 :       CALL dbcsr_deallocate_matrix_set(matrix_z0)
     838             : 
     839         132 :       DEALLOCATE (alpha, beta, new_norm, norm_cA, norm_rr)
     840         132 :       DEALLOCATE (tr_rz00)
     841             : 
     842         132 :       CALL timestop(handle)
     843             : 
     844         396 :    END SUBROUTINE ec_response_ao
     845             : 
     846             : ! **************************************************************************************************
     847             : !> \brief Compute matrix_wz as needed for the forces
     848             : !>        Wz = 0.5*(Z*KS*P + P*KS*Z) (closed-shell)
     849             : !> \param qs_env ...
     850             : !> \param matrix_z The response density we just calculated
     851             : !> \param matrix_wz The energy weighted response-density matrix
     852             : !> \param eps_filter ...
     853             : !> \par History
     854             : !>       2020.2 created [Fabian Belleflamme]
     855             : !> \author Fabian Belleflamme
     856             : ! **************************************************************************************************
     857         132 :    SUBROUTINE ec_wz_matrix(qs_env, matrix_z, matrix_wz, eps_filter)
     858             : 
     859             :       TYPE(qs_environment_type), POINTER                 :: qs_env
     860             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(IN), &
     861             :          POINTER                                         :: matrix_z
     862             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(INOUT), &
     863             :          POINTER                                         :: matrix_wz
     864             :       REAL(KIND=dp), INTENT(IN)                          :: eps_filter
     865             : 
     866             :       CHARACTER(len=*), PARAMETER                        :: routineN = 'ec_wz_matrix'
     867             : 
     868             :       INTEGER                                            :: handle, ispin, nspins
     869             :       REAL(KIND=dp)                                      :: scaling
     870         132 :       TYPE(dbcsr_p_type), DIMENSION(:), POINTER          :: matrix_ks, matrix_p, matrix_s
     871             :       TYPE(dbcsr_type)                                   :: matrix_tmp, matrix_tmp2
     872             :       TYPE(dft_control_type), POINTER                    :: dft_control
     873             :       TYPE(qs_rho_type), POINTER                         :: rho
     874             : 
     875         132 :       CALL timeset(routineN, handle)
     876             : 
     877         132 :       CPASSERT(ASSOCIATED(qs_env))
     878         132 :       CPASSERT(ASSOCIATED(matrix_z))
     879         132 :       CPASSERT(ASSOCIATED(matrix_wz))
     880             : 
     881             :       CALL get_qs_env(qs_env=qs_env, &
     882             :                       dft_control=dft_control, &
     883             :                       matrix_ks=matrix_ks, &
     884             :                       matrix_s=matrix_s, &
     885         132 :                       rho=rho)
     886         132 :       nspins = dft_control%nspins
     887             : 
     888         132 :       CALL qs_rho_get(rho, rho_ao=matrix_p)
     889             : 
     890             :       ! Init temp matrices
     891             :       CALL dbcsr_create(matrix_tmp, template=matrix_z(1)%matrix, &
     892         132 :                         matrix_type=dbcsr_type_no_symmetry)
     893             :       CALL dbcsr_create(matrix_tmp2, template=matrix_z(1)%matrix, &
     894         132 :                         matrix_type=dbcsr_type_no_symmetry)
     895             : 
     896             :       ! Scale matrix_p by factor 1/2 in closed-shell
     897         132 :       scaling = 1.0_dp
     898         132 :       IF (nspins == 1) scaling = 0.5_dp
     899             : 
     900             :       ! Whz = ZFP + PFZ = Z(FP) + (Z(FP))^T
     901         264 :       DO ispin = 1, nspins
     902             : 
     903             :          ! tmp = FP
     904             :          CALL dbcsr_multiply("N", "N", scaling, matrix_ks(ispin)%matrix, matrix_p(ispin)%matrix, &
     905         132 :                              0.0_dp, matrix_tmp, filter_eps=eps_filter, retain_sparsity=.FALSE.)
     906             : 
     907             :          ! tmp2 = ZFP
     908             :          CALL dbcsr_multiply("N", "N", 1.0_dp, matrix_z(ispin)%matrix, matrix_tmp, &
     909         132 :                              0.0_dp, matrix_tmp2, filter_eps=eps_filter, retain_sparsity=.FALSE.)
     910             : 
     911             :          ! tmp = (ZFP)^T
     912         132 :          CALL dbcsr_transposed(matrix_tmp, matrix_tmp2)
     913             : 
     914             :          ! tmp = ZFP + (ZFP)^T
     915         132 :          CALL dbcsr_add(matrix_tmp, matrix_tmp2, 1.0_dp, 1.0_dp)
     916             : 
     917         132 :          CALL dbcsr_filter(matrix_tmp, eps_filter)
     918             : 
     919             :          ! Whz = ZFP + PFZ
     920         264 :          CALL dbcsr_copy(matrix_wz(ispin)%matrix, matrix_tmp, keep_sparsity=.TRUE.)
     921             : 
     922             :       END DO
     923             : 
     924             :       ! Release matrices
     925         132 :       CALL dbcsr_release(matrix_tmp)
     926         132 :       CALL dbcsr_release(matrix_tmp2)
     927             : 
     928         132 :       CALL timestop(handle)
     929             : 
     930         132 :    END SUBROUTINE ec_wz_matrix
     931             : 
     932             : ! **************************************************************************************************
     933             : !> \brief  Calculate first term of electronic Hessian  M = [F, B]
     934             : !>         acting as liner transformation on trial matrix (matrix_cg)
     935             : !>         with intermediate response density  B = [cg,P] = cg*P - P*cg = cg*P + (cg*P)^T
     936             : !>
     937             : !>         All matrices are in orthonormal basis
     938             : !>
     939             : !> \param matrix_ks Ground-state Kohn-Sham matrix
     940             : !> \param matrix_p  Ground-state Density matrix
     941             : !> \param matrix_cg Trial matrix
     942             : !> \param matrix_b  Intermediate response density
     943             : !> \param matrix_Ax First term of electronic Hessian applied on trial matrix (matrix_cg)
     944             : !>
     945             : !> \param eps_filter ...
     946             : !> \date    12.2019
     947             : !> \author  Fabian Belleflamme
     948             : ! **************************************************************************************************
     949        4214 :    SUBROUTINE hessian_op1(matrix_ks, matrix_p, matrix_cg, matrix_b, matrix_Ax, eps_filter)
     950             : 
     951             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(IN), &
     952             :          POINTER                                         :: matrix_ks, matrix_p, matrix_cg
     953             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(INOUT), &
     954             :          POINTER                                         :: matrix_b, matrix_Ax
     955             :       REAL(KIND=dp), INTENT(IN)                          :: eps_filter
     956             : 
     957             :       CHARACTER(len=*), PARAMETER                        :: routineN = 'hessian_op1'
     958             : 
     959             :       INTEGER                                            :: handle
     960             : 
     961        4214 :       CALL timeset(routineN, handle)
     962             : 
     963        4214 :       CPASSERT(ASSOCIATED(matrix_ks))
     964        4214 :       CPASSERT(ASSOCIATED(matrix_p))
     965        4214 :       CPASSERT(ASSOCIATED(matrix_cg))
     966        4214 :       CPASSERT(ASSOCIATED(matrix_b))
     967        4214 :       CPASSERT(ASSOCIATED(matrix_Ax))
     968             : 
     969             :       ! Build intermediate density matrix
     970             :       ! B = [cg, P] = cg*P - P*cg = cg*P + (cg*P)^T
     971        4214 :       CALL commutator(matrix_cg, matrix_p, matrix_b, eps_filter, .TRUE.)
     972             : 
     973             :       ! Build first part of operator
     974             :       ! Ax = [F,[cg,P]] = [F,B]
     975        4214 :       CALL commutator(matrix_ks, matrix_b, matrix_Ax, eps_filter, .FALSE.)
     976             : 
     977        4214 :       CALL timestop(handle)
     978             : 
     979        4214 :    END SUBROUTINE hessian_op1
     980             : 
     981             : ! **************************************************************************************************
     982             : !> \brief  calculate linear transformation of Hessian matrix on a trial matrix matrix_cg
     983             : !>         which is stored in response density B = [cg,P] = cg*P - P*cg = cg*P + (cg*P)^T
     984             : !>         Ax = [F, B] + [G(B), Pin] in orthonormal basis
     985             : !>
     986             : !> \param qs_env ...
     987             : !> \param p_env ...
     988             : !> \param matrix_ks Ground-state Kohn-Sham matrix
     989             : !> \param matrix_p  Ground-state Density matrix
     990             : !> \param matrix_s_sqrt_inv S^(-1/2) needed for transformation to/from orthonormal basis
     991             : !> \param matrix_cg Trial matrix
     992             : !> \param matrix_Ax Electronic Hessian applied on trial matrix (matrix_cg)
     993             : !> \param eps_filter ...
     994             : !>
     995             : !> \date    12.2019
     996             : !> \author  Fabian Belleflamme
     997             : ! **************************************************************************************************
     998         580 :    SUBROUTINE build_hessian_op(qs_env, p_env, matrix_ks, matrix_p, matrix_s_sqrt_inv, &
     999             :                                matrix_cg, matrix_Ax, eps_filter)
    1000             : 
    1001             :       TYPE(qs_environment_type), POINTER                 :: qs_env
    1002             :       TYPE(qs_p_env_type), POINTER                       :: p_env
    1003             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(IN), &
    1004             :          POINTER                                         :: matrix_ks, matrix_p
    1005             :       TYPE(dbcsr_type), INTENT(IN)                       :: matrix_s_sqrt_inv
    1006             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(IN), &
    1007             :          POINTER                                         :: matrix_cg
    1008             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(INOUT), &
    1009             :          POINTER                                         :: matrix_Ax
    1010             :       REAL(KIND=dp), INTENT(IN)                          :: eps_filter
    1011             : 
    1012             :       CHARACTER(len=*), PARAMETER                        :: routineN = 'build_hessian_op'
    1013             : 
    1014             :       INTEGER                                            :: handle, ispin, nspins
    1015             :       REAL(KIND=dp)                                      :: chksum
    1016         580 :       TYPE(dbcsr_p_type), DIMENSION(:), POINTER          :: matrix_b, rho1_ao
    1017             :       TYPE(dft_control_type), POINTER                    :: dft_control
    1018             :       TYPE(mp_para_env_type), POINTER                    :: para_env
    1019             :       TYPE(qs_rho_type), POINTER                         :: rho
    1020             : 
    1021         580 :       CALL timeset(routineN, handle)
    1022             : 
    1023         580 :       CPASSERT(ASSOCIATED(qs_env))
    1024         580 :       CPASSERT(ASSOCIATED(matrix_ks))
    1025         580 :       CPASSERT(ASSOCIATED(matrix_p))
    1026         580 :       CPASSERT(ASSOCIATED(matrix_cg))
    1027         580 :       CPASSERT(ASSOCIATED(matrix_Ax))
    1028             : 
    1029             :       CALL get_qs_env(qs_env=qs_env, &
    1030             :                       dft_control=dft_control, &
    1031             :                       para_env=para_env, &
    1032         580 :                       rho=rho)
    1033         580 :       nspins = dft_control%nspins
    1034             : 
    1035         580 :       NULLIFY (matrix_b)
    1036         580 :       CALL dbcsr_allocate_matrix_set(matrix_b, nspins)
    1037        1160 :       DO ispin = 1, nspins
    1038         580 :          ALLOCATE (matrix_b(ispin)%matrix)
    1039             :          CALL dbcsr_create(matrix_b(ispin)%matrix, name="[X,P] RSP DNSTY", &
    1040             :                            template=matrix_p(1)%matrix, &
    1041        1160 :                            matrix_type=dbcsr_type_no_symmetry)
    1042             :       END DO
    1043             : 
    1044             :       ! Build uncoupled term of Hessian linear transformation
    1045         580 :       CALL hessian_op1(matrix_ks, matrix_p, matrix_cg, matrix_b, matrix_Ax, eps_filter)
    1046             : 
    1047             :       ! Avoid the buildup of noisy blocks
    1048        1160 :       DO ispin = 1, nspins
    1049        1160 :          CALL dbcsr_filter(matrix_b(ispin)%matrix, eps_filter)
    1050             :       END DO
    1051             : 
    1052             :       chksum = 0.0_dp
    1053        1160 :       DO ispin = 1, nspins
    1054        1160 :          chksum = chksum + dbcsr_checksum(matrix_b(ispin)%matrix)
    1055             :       END DO
    1056             : 
    1057             :       ! skip the kernel if the DM is very small
    1058         580 :       IF (chksum .GT. 1.0E-14_dp) THEN
    1059             : 
    1060             :          ! Bring matrix B as density on grid
    1061             : 
    1062             :          ! prepare perturbation environment
    1063         576 :          CALL p_env_check_i_alloc(p_env, qs_env)
    1064             : 
    1065             :          ! Get response density matrix
    1066         576 :          CALL qs_rho_get(p_env%rho1, rho_ao=rho1_ao)
    1067             : 
    1068        1152 :          DO ispin = 1, nspins
    1069             :             ! Transform B into NON-ortho basis for collocation
    1070         576 :             CALL transform_m_orth(matrix_b(ispin)%matrix, matrix_s_sqrt_inv, eps_filter)
    1071             :             ! Filter
    1072         576 :             CALL dbcsr_filter(matrix_b(ispin)%matrix, eps_filter)
    1073             :             ! Keep symmetry of density matrix
    1074         576 :             CALL dbcsr_copy(rho1_ao(ispin)%matrix, matrix_b(ispin)%matrix, keep_sparsity=.TRUE.)
    1075        1152 :             CALL dbcsr_copy(p_env%p1(ispin)%matrix, matrix_b(ispin)%matrix, keep_sparsity=.TRUE.)
    1076             :          END DO
    1077             : 
    1078             :          ! Updates densities on grid wrt density matrix
    1079         576 :          CALL p_env_update_rho(p_env, qs_env)
    1080             : 
    1081        1152 :          DO ispin = 1, nspins
    1082         576 :             CALL dbcsr_set(p_env%kpp1(ispin)%matrix, 0.0_dp)
    1083        1152 :             IF (ASSOCIATED(p_env%kpp1_admm)) CALL dbcsr_set(p_env%kpp1_admm(ispin)%matrix, 0.0_dp)
    1084             :          END DO
    1085             : 
    1086             :          ! Calculate kernel
    1087             :          ! Ax = F*B - B*F + G(B)*P - P*G(B)
    1088             :          !                               IN/OUT     IN        IN                 IN
    1089         576 :          CALL hessian_op2(qs_env, p_env, matrix_Ax, matrix_p, matrix_s_sqrt_inv, eps_filter)
    1090             : 
    1091             :       END IF
    1092             : 
    1093         580 :       CALL dbcsr_deallocate_matrix_set(matrix_b)
    1094             : 
    1095         580 :       CALL timestop(handle)
    1096             : 
    1097         580 :    END SUBROUTINE build_hessian_op
    1098             : 
    1099             : ! **************************************************************************************************
    1100             : !> \brief  Calculate lin transformation of Hessian matrix on a trial matrix matrix_cg
    1101             : !>         which is stored in response density B = [cg,P] = cg*P - P*cg = cg*P + (cg*P)^T
    1102             : !>         Ax = [F, B] + [G(B), Pin] in orthonormal basis
    1103             : !>
    1104             : !> \param qs_env ...
    1105             : !> \param p_env p-environment with trial density environment
    1106             : !> \param matrix_Ax contains first part of Hessian linear transformation, kernel contribution
    1107             : !>                  is calculated and added in this routine
    1108             : !> \param matrix_p Density matrix in orthogonal basis
    1109             : !> \param matrix_s_sqrt_inv contains matrix S^(-1/2) for switching to orthonormal Lowdin basis
    1110             : !> \param eps_filter ...
    1111             : !>
    1112             : !> \date    12.2019
    1113             : !> \author  Fabian Belleflamme
    1114             : ! **************************************************************************************************
    1115         576 :    SUBROUTINE hessian_op2(qs_env, p_env, matrix_Ax, matrix_p, matrix_s_sqrt_inv, eps_filter)
    1116             : 
    1117             :       TYPE(qs_environment_type), POINTER                 :: qs_env
    1118             :       TYPE(qs_p_env_type), POINTER                       :: p_env
    1119             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(INOUT), &
    1120             :          POINTER                                         :: matrix_Ax
    1121             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(IN), &
    1122             :          POINTER                                         :: matrix_p
    1123             :       TYPE(dbcsr_type), INTENT(IN)                       :: matrix_s_sqrt_inv
    1124             :       REAL(KIND=dp), INTENT(IN)                          :: eps_filter
    1125             : 
    1126             :       CHARACTER(len=*), PARAMETER                        :: routineN = 'hessian_op2'
    1127             : 
    1128             :       INTEGER                                            :: handle, ispin, nspins
    1129             :       REAL(KIND=dp)                                      :: ekin_mol
    1130             :       TYPE(admm_type), POINTER                           :: admm_env
    1131         576 :       TYPE(dbcsr_p_type), DIMENSION(:), POINTER          :: matrix_G, matrix_s, rho1_ao, rho_ao
    1132             :       TYPE(dft_control_type), POINTER                    :: dft_control
    1133             :       TYPE(mp_para_env_type), POINTER                    :: para_env
    1134             :       TYPE(pw_c1d_gs_type)                               :: rho_tot_gspace, v_hartree_gspace
    1135         576 :       TYPE(pw_c1d_gs_type), DIMENSION(:), POINTER        :: rho1_g
    1136             :       TYPE(pw_env_type), POINTER                         :: pw_env
    1137             :       TYPE(pw_poisson_type), POINTER                     :: poisson_env
    1138         576 :       TYPE(pw_pool_p_type), DIMENSION(:), POINTER        :: pw_pools
    1139             :       TYPE(pw_pool_type), POINTER                        :: auxbas_pw_pool
    1140             :       TYPE(pw_r3d_rs_type)                               :: v_hartree_rspace
    1141         576 :       TYPE(pw_r3d_rs_type), DIMENSION(:), POINTER        :: rho1_r, rho_r, tau1_r, v_xc, v_xc_tau
    1142             :       TYPE(qs_kpp1_env_type), POINTER                    :: kpp1_env
    1143             :       TYPE(qs_rho_type), POINTER                         :: rho, rho_aux
    1144             :       TYPE(section_vals_type), POINTER                   :: input, xc_section, xc_section_aux
    1145             : 
    1146         576 :       CALL timeset(routineN, handle)
    1147             : 
    1148         576 :       NULLIFY (admm_env, dft_control, input, matrix_s, para_env, rho, rho_r, rho1_g, rho1_r)
    1149             : 
    1150             :       CALL get_qs_env(qs_env=qs_env, &
    1151             :                       admm_env=admm_env, &
    1152             :                       dft_control=dft_control, &
    1153             :                       input=input, &
    1154             :                       matrix_s=matrix_s, &
    1155             :                       para_env=para_env, &
    1156         576 :                       rho=rho)
    1157         576 :       nspins = dft_control%nspins
    1158             : 
    1159         576 :       CPASSERT(ASSOCIATED(p_env%kpp1))
    1160         576 :       CPASSERT(ASSOCIATED(p_env%kpp1_env))
    1161         576 :       kpp1_env => p_env%kpp1_env
    1162             : 
    1163             :       ! Get non-ortho input density matrix on grid
    1164         576 :       CALL qs_rho_get(rho, rho_ao=rho_ao)
    1165             :       ! Get non-ortho trial density stored in p_env
    1166         576 :       CALL qs_rho_get(p_env%rho1, rho_g=rho1_g, rho_r=rho1_r, tau_r=tau1_r)
    1167             : 
    1168         576 :       NULLIFY (pw_env)
    1169         576 :       CALL get_qs_env(qs_env, pw_env=pw_env)
    1170         576 :       CPASSERT(ASSOCIATED(pw_env))
    1171             : 
    1172         576 :       NULLIFY (auxbas_pw_pool, poisson_env, pw_pools)
    1173             :       ! gets the tmp grids
    1174             :       CALL pw_env_get(pw_env=pw_env, &
    1175             :                       auxbas_pw_pool=auxbas_pw_pool, &
    1176             :                       pw_pools=pw_pools, &
    1177         576 :                       poisson_env=poisson_env)
    1178             : 
    1179             :       ! Calculate the NSC Hartree potential
    1180         576 :       CALL auxbas_pw_pool%create_pw(pw=v_hartree_gspace)
    1181         576 :       CALL auxbas_pw_pool%create_pw(pw=rho_tot_gspace)
    1182         576 :       CALL auxbas_pw_pool%create_pw(pw=v_hartree_rspace)
    1183             : 
    1184             :       ! XC-Kernel
    1185         576 :       NULLIFY (v_xc, v_xc_tau, xc_section)
    1186             : 
    1187         576 :       IF (dft_control%do_admm) THEN
    1188         132 :          xc_section => admm_env%xc_section_primary
    1189             :       ELSE
    1190         444 :          xc_section => section_vals_get_subs_vals(input, "DFT%XC")
    1191             :       END IF
    1192             : 
    1193             :       ! add xc-kernel
    1194             :       CALL create_kernel(qs_env, &
    1195             :                          vxc=v_xc, &
    1196             :                          vxc_tau=v_xc_tau, &
    1197             :                          rho=rho, &
    1198             :                          rho1_r=rho1_r, &
    1199             :                          rho1_g=rho1_g, &
    1200             :                          tau1_r=tau1_r, &
    1201         576 :                          xc_section=xc_section)
    1202             : 
    1203        1152 :       DO ispin = 1, nspins
    1204         576 :          CALL pw_scale(v_xc(ispin), v_xc(ispin)%pw_grid%dvol)
    1205        1152 :          IF (ASSOCIATED(v_xc_tau)) THEN
    1206          24 :             CALL pw_scale(v_xc_tau(ispin), v_xc_tau(ispin)%pw_grid%dvol)
    1207             :          END IF
    1208             :       END DO
    1209             : 
    1210             :       ! ADMM Correction
    1211         576 :       IF (dft_control%do_admm) THEN
    1212         132 :          IF (admm_env%aux_exch_func /= do_admm_aux_exch_func_none) THEN
    1213          70 :             IF (.NOT. ASSOCIATED(kpp1_env%deriv_set_admm)) THEN
    1214          16 :                xc_section_aux => admm_env%xc_section_aux
    1215          16 :                CALL get_admm_env(qs_env%admm_env, rho_aux_fit=rho_aux)
    1216          16 :                CALL qs_rho_get(rho_aux, rho_r=rho_r)
    1217         368 :                ALLOCATE (kpp1_env%deriv_set_admm, kpp1_env%rho_set_admm)
    1218             :                CALL xc_prep_2nd_deriv(kpp1_env%deriv_set_admm, kpp1_env%rho_set_admm, &
    1219             :                                       rho_r, auxbas_pw_pool, &
    1220          16 :                                       xc_section=xc_section_aux)
    1221             :             END IF
    1222             :          END IF
    1223             :       END IF
    1224             : 
    1225             :       ! take trial density to build G^{H}[B]
    1226         576 :       CALL pw_zero(rho_tot_gspace)
    1227        1152 :       DO ispin = 1, nspins
    1228        1152 :          CALL pw_axpy(rho1_g(ispin), rho_tot_gspace)
    1229             :       END DO
    1230             : 
    1231             :       ! get Hartree potential from rho_tot_gspace
    1232             :       CALL pw_poisson_solve(poisson_env, rho_tot_gspace, &
    1233         576 :                             vhartree=v_hartree_gspace)
    1234         576 :       CALL pw_transfer(v_hartree_gspace, v_hartree_rspace)
    1235         576 :       CALL pw_scale(v_hartree_rspace, v_hartree_rspace%pw_grid%dvol)
    1236             : 
    1237             :       ! Add v_xc + v_H
    1238        1152 :       DO ispin = 1, nspins
    1239        1152 :          CALL pw_axpy(v_hartree_rspace, v_xc(ispin))
    1240             :       END DO
    1241         576 :       IF (nspins == 1) THEN
    1242         576 :          CALL pw_scale(v_xc(1), 2.0_dp)
    1243         576 :          IF (ASSOCIATED(v_xc_tau)) CALL pw_scale(v_xc_tau(1), 2.0_dp)
    1244             :       END IF
    1245             : 
    1246        1152 :       DO ispin = 1, nspins
    1247             :          ! Integrate with ground-state density matrix, in non-orthogonal basis
    1248             :          CALL integrate_v_rspace(v_rspace=v_xc(ispin), &
    1249             :                                  pmat=rho_ao(ispin), &
    1250             :                                  hmat=p_env%kpp1(ispin), &
    1251             :                                  qs_env=qs_env, &
    1252             :                                  calculate_forces=.FALSE., &
    1253         576 :                                  basis_type="ORB")
    1254        1152 :          IF (ASSOCIATED(v_xc_tau)) THEN
    1255             :             CALL integrate_v_rspace(v_rspace=v_xc_tau(ispin), &
    1256             :                                     pmat=rho_ao(ispin), &
    1257             :                                     hmat=p_env%kpp1(ispin), &
    1258             :                                     qs_env=qs_env, &
    1259             :                                     compute_tau=.TRUE., &
    1260             :                                     calculate_forces=.FALSE., &
    1261          24 :                                     basis_type="ORB")
    1262             :          END IF
    1263             :       END DO
    1264             : 
    1265             :       ! Hartree-Fock contribution
    1266         576 :       CALL apply_hfx(qs_env, p_env)
    1267             :       ! Calculate ADMM exchange correction to kernel
    1268         576 :       CALL apply_xc_admm(qs_env, p_env)
    1269             :       ! Add contribution from ADMM exchange correction to kernel
    1270         576 :       CALL p_env_finish_kpp1(qs_env, p_env)
    1271             : 
    1272             :       ! Calculate KG correction to kernel
    1273         576 :       IF (dft_control%qs_control%do_kg) THEN
    1274          50 :          IF (qs_env%kg_env%tnadd_method == kg_tnadd_embed .OR. &
    1275             :              qs_env%kg_env%tnadd_method == kg_tnadd_embed_ri) THEN
    1276             : 
    1277          24 :             CPASSERT(dft_control%nimages == 1)
    1278             :             ekin_mol = 0.0_dp
    1279          24 :             CALL qs_rho_get(p_env%rho1, rho_ao=rho1_ao)
    1280             :             CALL kg_ekin_subset(qs_env=qs_env, &
    1281             :                                 ks_matrix=p_env%kpp1, &
    1282             :                                 ekin_mol=ekin_mol, &
    1283             :                                 calc_force=.FALSE., &
    1284             :                                 do_kernel=.TRUE., &
    1285          24 :                                 pmat_ext=rho1_ao)
    1286             :          END IF
    1287             :       END IF
    1288             : 
    1289             :       ! Init response kernel matrix
    1290             :       ! matrix G(B)
    1291         576 :       NULLIFY (matrix_G)
    1292         576 :       CALL dbcsr_allocate_matrix_set(matrix_G, nspins)
    1293        1152 :       DO ispin = 1, nspins
    1294         576 :          ALLOCATE (matrix_G(ispin)%matrix)
    1295             :          CALL dbcsr_copy(matrix_G(ispin)%matrix, p_env%kpp1(ispin)%matrix, &
    1296        1152 :                          name="MATRIX Kernel")
    1297             :       END DO
    1298             : 
    1299             :       ! Transforming G(B) into orthonormal basis
    1300             :       ! Careful, this de-symmetrizes matrix_G
    1301        1152 :       DO ispin = 1, nspins
    1302         576 :          CALL transform_m_orth(matrix_G(ispin)%matrix, matrix_s_sqrt_inv, eps_filter)
    1303        1152 :          CALL dbcsr_filter(matrix_G(ispin)%matrix, eps_filter)
    1304             :       END DO
    1305             : 
    1306             :       ! Hessian already contains  Ax = [F,B] (ORTHO), now adding
    1307             :       ! Ax = Ax + G(B)P - (G(B)P)^T
    1308         576 :       CALL commutator(matrix_G, matrix_p, matrix_Ax, eps_filter, .FALSE., 1.0_dp, 1.0_dp)
    1309             : 
    1310             :       ! release pw grids
    1311         576 :       CALL auxbas_pw_pool%give_back_pw(v_hartree_gspace)
    1312         576 :       CALL auxbas_pw_pool%give_back_pw(v_hartree_rspace)
    1313         576 :       CALL auxbas_pw_pool%give_back_pw(rho_tot_gspace)
    1314        1152 :       DO ispin = 1, nspins
    1315        1152 :          CALL auxbas_pw_pool%give_back_pw(v_xc(ispin))
    1316             :       END DO
    1317         576 :       DEALLOCATE (v_xc)
    1318         576 :       IF (ASSOCIATED(v_xc_tau)) THEN
    1319          48 :          DO ispin = 1, nspins
    1320          48 :             CALL auxbas_pw_pool%give_back_pw(v_xc_tau(ispin))
    1321             :          END DO
    1322          24 :          DEALLOCATE (v_xc_tau)
    1323             :       END IF
    1324             : 
    1325         576 :       CALL dbcsr_deallocate_matrix_set(matrix_G)
    1326             : 
    1327         576 :       CALL timestop(handle)
    1328             : 
    1329         576 :    END SUBROUTINE hessian_op2
    1330             : 
    1331             : ! **************************************************************************************************
    1332             : !> \brief computes (anti-)commutator exploiting (anti-)symmetry:
    1333             : !>        A symmetric : RES = beta*RES + k*[A,B] = k*(AB-(AB)^T)
    1334             : !>        A anti-sym  : RES = beta*RES + k*{A,B} = k*(AB+(AB)^T)
    1335             : !>
    1336             : !> \param a          Matrix A
    1337             : !> \param b          Matrix B
    1338             : !> \param res        Commutator result
    1339             : !> \param eps_filter filtering threshold for sparse matrices
    1340             : !> \param anticomm   Calculate anticommutator
    1341             : !> \param alpha      Scaling of anti-/commutator
    1342             : !> \param beta       Scaling of inital content of result matrix
    1343             : !>
    1344             : !> \par History
    1345             : !>       2020.07 Fabian Belleflamme  (based on commutator_symm)
    1346             : ! **************************************************************************************************
    1347        9268 :    SUBROUTINE commutator(a, b, res, eps_filter, anticomm, alpha, beta)
    1348             : 
    1349             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(IN), &
    1350             :          POINTER                                         :: a, b, res
    1351             :       REAL(KIND=dp)                                      :: eps_filter
    1352             :       LOGICAL                                            :: anticomm
    1353             :       REAL(KIND=dp), OPTIONAL                            :: alpha, beta
    1354             : 
    1355             :       CHARACTER(LEN=*), PARAMETER                        :: routineN = 'commutator'
    1356             : 
    1357             :       INTEGER                                            :: handle, ispin
    1358             :       REAL(KIND=dp)                                      :: facc, myalpha, mybeta
    1359             :       TYPE(dbcsr_type)                                   :: work, work2
    1360             : 
    1361        9268 :       CALL timeset(routineN, handle)
    1362             : 
    1363        9268 :       CPASSERT(ASSOCIATED(a))
    1364        9268 :       CPASSERT(ASSOCIATED(b))
    1365        9268 :       CPASSERT(ASSOCIATED(res))
    1366             : 
    1367        9268 :       CALL dbcsr_create(work, template=a(1)%matrix, matrix_type=dbcsr_type_no_symmetry)
    1368        9268 :       CALL dbcsr_create(work2, template=a(1)%matrix, matrix_type=dbcsr_type_no_symmetry)
    1369             : 
    1370             :       ! Scaling of anti-/commutator
    1371        9268 :       myalpha = 1.0_dp
    1372        9268 :       IF (PRESENT(alpha)) myalpha = alpha
    1373             :       ! Scaling of result matrix
    1374        9268 :       mybeta = 0.0_dp
    1375        9268 :       IF (PRESENT(beta)) mybeta = beta
    1376             :       ! Add/subtract second term when calculating anti-/commutator
    1377        9268 :       facc = -1.0_dp
    1378        9268 :       IF (anticomm) facc = 1.0_dp
    1379             : 
    1380       18536 :       DO ispin = 1, SIZE(a)
    1381             : 
    1382             :          CALL dbcsr_multiply("N", "N", myalpha, a(ispin)%matrix, b(ispin)%matrix, &
    1383        9268 :                              0.0_dp, work, filter_eps=eps_filter)
    1384        9268 :          CALL dbcsr_transposed(work2, work)
    1385             : 
    1386             :          ! RES= beta*RES + alpha*{A,B} = beta*RES + alpha*[AB+(AB)T]
    1387             :          ! RES= beta*RES + alpha*[A,B] = beta*RES + alpha*[AB-(AB)T]
    1388        9268 :          CALL dbcsr_add(work, work2, 1.0_dp, facc)
    1389             : 
    1390       18536 :          CALL dbcsr_add(res(ispin)%matrix, work, mybeta, 1.0_dp)
    1391             : 
    1392             :       END DO
    1393             : 
    1394        9268 :       CALL dbcsr_release(work)
    1395        9268 :       CALL dbcsr_release(work2)
    1396             : 
    1397        9268 :       CALL timestop(handle)
    1398             : 
    1399        9268 :    END SUBROUTINE commutator
    1400             : 
    1401             : ! **************************************************************************************************
    1402             : !> \brief Projector P(M) = P*M*Q^T + Q*M*P^T
    1403             : !>        with P = D
    1404             : !>        with Q = (1-D)
    1405             : !>
    1406             : !> \param qs_env ...
    1407             : !> \param matrix_p  Ground-state density in orthonormal basis
    1408             : !> \param matrix_io Matrix to which projector is applied.
    1409             : !>
    1410             : !> \param eps_filter ...
    1411             : !> \date    06.2020
    1412             : !> \author  Fabian Belleflamme
    1413             : ! **************************************************************************************************
    1414        5498 :    SUBROUTINE projector(qs_env, matrix_p, matrix_io, eps_filter)
    1415             : 
    1416             :       TYPE(qs_environment_type), POINTER                 :: qs_env
    1417             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(IN), &
    1418             :          POINTER                                         :: matrix_p
    1419             :       TYPE(dbcsr_p_type), DIMENSION(:), INTENT(INOUT), &
    1420             :          POINTER                                         :: matrix_io
    1421             :       REAL(KIND=dp), INTENT(IN)                          :: eps_filter
    1422             : 
    1423             :       CHARACTER(len=*), PARAMETER                        :: routineN = 'projector'
    1424             : 
    1425             :       INTEGER                                            :: handle, ispin, nspins
    1426             :       TYPE(dbcsr_type)                                   :: matrix_q, matrix_tmp
    1427             :       TYPE(dft_control_type), POINTER                    :: dft_control
    1428             :       TYPE(mp_para_env_type), POINTER                    :: para_env
    1429             : 
    1430        5498 :       CALL timeset(routineN, handle)
    1431             : 
    1432             :       CALL get_qs_env(qs_env=qs_env, &
    1433             :                       dft_control=dft_control, &
    1434        5498 :                       para_env=para_env)
    1435        5498 :       nspins = dft_control%nspins
    1436             : 
    1437             :       CALL dbcsr_create(matrix_q, template=matrix_p(1)%matrix, &
    1438        5498 :                         matrix_type=dbcsr_type_no_symmetry)
    1439             :       CALL dbcsr_create(matrix_tmp, template=matrix_p(1)%matrix, &
    1440        5498 :                         matrix_type=dbcsr_type_no_symmetry)
    1441             : 
    1442             :       ! Q = (1 - P)
    1443        5498 :       CALL dbcsr_copy(matrix_q, matrix_p(1)%matrix)
    1444        5498 :       CALL dbcsr_scale(matrix_q, -1.0_dp)
    1445        5498 :       CALL dbcsr_add_on_diag(matrix_q, 1.0_dp)
    1446        5498 :       CALL dbcsr_finalize(matrix_q)
    1447             : 
    1448             :       ! Proj(M) = P*M*Q + Q*M*P
    1449             :       ! with P = D = CC^T
    1450             :       ! and  Q = (1 - P)
    1451       10996 :       DO ispin = 1, nspins
    1452             : 
    1453             :          ! tmp1 = P*M
    1454             :          CALL dbcsr_multiply("N", "N", 1.0_dp, matrix_p(ispin)%matrix, matrix_io(ispin)%matrix, &
    1455        5498 :                              0.0_dp, matrix_tmp, filter_eps=eps_filter)
    1456             :          ! m_io = P*M*Q
    1457             :          CALL dbcsr_multiply("N", "N", 1.0_dp, matrix_tmp, matrix_q, &
    1458        5498 :                              0.0_dp, matrix_io(ispin)%matrix, filter_eps=eps_filter)
    1459             : 
    1460             :          ! tmp = (P^T*M^T*Q^T)^T = -(P*M*Q)^T
    1461        5498 :          CALL dbcsr_transposed(matrix_tmp, matrix_io(ispin)%matrix)
    1462       10996 :          CALL dbcsr_add(matrix_io(ispin)%matrix, matrix_tmp, 1.0_dp, -1.0_dp)
    1463             : 
    1464             :       END DO
    1465             : 
    1466        5498 :       CALL dbcsr_release(matrix_tmp)
    1467        5498 :       CALL dbcsr_release(matrix_q)
    1468             : 
    1469        5498 :       CALL timestop(handle)
    1470             : 
    1471        5498 :    END SUBROUTINE projector
    1472             : 
    1473             : ! **************************************************************************************************
    1474             : !> \brief performs a tranformation of a matrix back to/into orthonormal basis
    1475             : !>        in case of P a scaling of 0.5 has to be applied for closed shell case
    1476             : !> \param matrix       matrix to be transformed
    1477             : !> \param matrix_trafo transformation matrix
    1478             : !> \param eps_filter   filtering threshold for sparse matrices
    1479             : !> \par History
    1480             : !>       2012.05 created [Florian Schiffmann]
    1481             : !> \author Florian Schiffmann
    1482             : !>
    1483             : ! **************************************************************************************************
    1484             : 
    1485        1680 :    SUBROUTINE transform_m_orth(matrix, matrix_trafo, eps_filter)
    1486             :       TYPE(dbcsr_type)                                   :: matrix, matrix_trafo
    1487             :       REAL(KIND=dp)                                      :: eps_filter
    1488             : 
    1489             :       CHARACTER(LEN=*), PARAMETER                        :: routineN = 'transform_m_orth'
    1490             : 
    1491             :       INTEGER                                            :: handle
    1492             :       TYPE(dbcsr_type)                                   :: matrix_tmp, matrix_work
    1493             : 
    1494        1680 :       CALL timeset(routineN, handle)
    1495             : 
    1496        1680 :       CALL dbcsr_create(matrix_work, template=matrix, matrix_type=dbcsr_type_no_symmetry)
    1497        1680 :       CALL dbcsr_create(matrix_tmp, template=matrix, matrix_type=dbcsr_type_no_symmetry)
    1498             : 
    1499             :       CALL dbcsr_multiply("N", "N", 1.0_dp, matrix, matrix_trafo, &
    1500        1680 :                           0.0_dp, matrix_work, filter_eps=eps_filter)
    1501             :       CALL dbcsr_multiply("N", "N", 1.0_dp, matrix_trafo, matrix_work, &
    1502        1680 :                           0.0_dp, matrix_tmp, filter_eps=eps_filter)
    1503             :       ! symmetrize results (this is again needed to make sure everything is stable)
    1504        1680 :       CALL dbcsr_transposed(matrix_work, matrix_tmp)
    1505        1680 :       CALL dbcsr_add(matrix_tmp, matrix_work, 0.5_dp, 0.5_dp)
    1506        1680 :       CALL dbcsr_copy(matrix, matrix_tmp)
    1507             : 
    1508             :       ! Avoid the buildup of noisy blocks
    1509        1680 :       CALL dbcsr_filter(matrix, eps_filter)
    1510             : 
    1511        1680 :       CALL dbcsr_release(matrix_tmp)
    1512        1680 :       CALL dbcsr_release(matrix_work)
    1513        1680 :       CALL timestop(handle)
    1514             : 
    1515        1680 :    END SUBROUTINE transform_m_orth
    1516             : 
    1517             : END MODULE ec_orth_solver

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