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--- howto:gw [2021/04/21 20:51] – jwilhelm
+++ howto:gw [2021/04/28 18:31] – Remove periodic GW part jwilhelm
@@ Line 165: / Line 165: @@
 "SC_GW0_ITER 10" means that at most ten iterations in the eigenvalues of G are performed. In case convergence is found, the code terminates earlier. "SC_GW0_ITER 1" corresponds to G0W0.
-===== 5. Periodic GW calculations =====
-For periodic GW calculations, a special correction scheme is necessary. A similar problem is appearing in Hartree-Fock calculations. In HF, an easy way out is given by the truncation of the Coulomb operator which works due to the convenient form of the HF equations. GW does not exhibit this convenient form and therefore, this truncation does not work for GW calculations. The theory why a correction is necessary and the correction scheme is described in [[doi>10.1103/PhysRevB.95.235123]].
-The basis can be found in {{exercises:2017_uzh_cp2k-tutorial:LiH_BASIS_RI.tar ?direct&400 |}}. Then run the calculation as listed below. The computed gap of LiH with the input from below should be 6.05 eV which is still significantly off from the converged result of 4.7 eV from [[doi>10.1103/PhysRevB.95.235123]]. Here, a basis set extrapolation (as shown above) and a larger supercell are necessary to get closer to the result of 4.7 eV. Please redo the calculation without the flag PERIODIC in the GW section and see that the resulting gap of 11.25 eV is much more off than the gap with correction.
-<code - LiH_periodic.inp>
-&FORCE_EVAL
-  METHOD Quickstep
-  &DFT
-    BASIS_SET_FILE_NAME ./LiH_BASIS_RI
-    POTENTIAL_FILE_NAME POTENTIAL
-    &MGRID
-      CUTOFF 600
-      REL_CUTOFF 60
-    &END MGRID
-    &QS
-      METHOD GPW
-      EPS_DEFAULT 1.0E-15
-      EPS_PGF_ORB 1.0E-20
-      EPS_FILTER_MATRIX 0.0e0
-    &END QS
-    &SCF
-      EPS_SCF 1.0E-6
-      MAX_SCF 100
-    &END SCF
-    &XC
-      &XC_FUNCTIONAL PBE
-      &END XC_FUNCTIONAL
-      &WF_CORRELATION
-        &RI_RPA
-          QUADRATURE_POINTS  100
-          &GW
-           CORR_OCC  5
-           CORR_VIRT 5
-           ! activate the periodic correction
-           PERIODIC
-          &END GW
-          ! HF calculation for the exchange part of the self-energy
-          ! Here, the truncation of the Coulomb operator works
-          &HF
-            &SCREENING
-              ! for other materials, a smaller EPS_SCHWARZ might be necessary
-              EPS_SCHWARZ 1.0E-6
-              SCREEN_ON_INITIAL_P TRUE
-            &END
-            &INTERACTION_POTENTIAL
-              POTENTIAL_TYPE TRUNCATED
-              ! the truncation radius is half the cell size
-              CUTOFF_RADIUS  2.00
-              T_C_G_DATA t_c_g.dat
-            &END
-            &MEMORY
-              MAX_MEMORY  0
-            &END
-          &END
-        &END RI_RPA
-        NUMBER_PROC  1
-      &END
-    &END XC
-  &END DFT
-  &SUBSYS
-    &CELL
-      ABC  4.084 4.084 4.084
-    &END CELL
-    &COORD
-      Li 0 0 0
-      Li 2.042 2.042 0
-      Li 2.042 0 2.042
-      Li 0 2.042 2.042
-      H 0 2.042 0
-      H 0 0 2.042
-      H 2.042 0 0
-      H 2.042 2.042 2.042
-    &END COORD
-    &KIND H
-      BASIS_SET cc-DZVP-GTH
-      BASIS_SET RI_AUX RI_DZ_opt_basis
-      POTENTIAL GTH-PBE-q1
-    &END KIND
-    &KIND Li
-      BASIS_SET cc-DZVP-GTH
-      BASIS_SET RI_AUX RI_DZ_opt_basis
-      POTENTIAL GTH-PBE-q3
-    &END KIND
-  &END SUBSYS
-&END FORCE_EVAL
-&GLOBAL
-  PROJECT     LiH_bulk_2x2x2_DZVP
-  PRINT_LEVEL MEDIUM
-  RUN_TYPE ENERGY
-&END GLOBAL
-</code>