In this exercise, we will look at a more complicated example than in Exercise 1, namely liquid water. We start by computing the PDOS and compare it the single H$_2$O molecules. This time we will have many more orbitals so in order to visualize our results, we will apply a Gaussian broadening to the results. After, we will do a short Born-Oppenheimer MD run and learn how the basic input and output.

In this part of the exerise we will compute the PDOS. Our model water will contain 64 H$_2$O molecules in a 12 Å box under periodic boundary conditions. The input is very similar to the first exercise, but since we now have a much more coordinates, it is convinient to import them from a separate file. Below is a an example input you can use to perform a single-point calculation extracting the PDOS.

liquid_water.inp

&GLOBAL
  PROJECT liquid_water
  RUN_TYPE ENERGY
  IOLEVEL LOW
&END GLOBAL

&FORCE_EVAL
  METHOD QS
  &DFT
    BASIS_SET_FILE_NAME GTH_BASIS_SETS
    POTENTIAL_FILE_NAME GTH_POTENTIALS
    LSD 0
    &QS
      METHOD GPW      
      EPS_DEFAULT 1.0E-10
    &END QS
    &SCF
      MAX_SCF    300
      EPS_SCF    1.0E-06
      SCF_GUESS  ATOMIC
      &MIXING
        METHOD DIRECT_P_MIXING
        ALPHA   0.45
      &END MIXING
      &DIAGONALIZATION
	      ALGORITHM STANDARD
      &END DIAGONALIZATION
      &PRINT
        &RESTART
          BACKUP_COPIES 0
        &END
      &END PRINT       
    &END SCF
    &MGRID
      NGRIDS 4
      CUTOFF 300
      REL_CUTOFF 60
    &END
    &XC
      &XC_FUNCTIONAL BLYP
      &END XC_FUNCTIONAL
    &END XC
        &PRINT
    &PDOS
      FILENAME ./liquid_water
    &END PDOS
    &END PRINT
  &END DFT
  &SUBSYS
    &CELL
      ABC 12.4170 12.4170 12.4170
      ANGLES 90.00 90.00 90.00
    &END CELL
    &TOPOLOGY
      COORD_FILE_FORMAT XYZ
      COORD_FILE_NAME liquid_water.xyz
      CONNECTIVITY OFF
    &END TOPOLOGY
    &KIND H             
      BASIS_SET DZVP-GTH
      POTENTIAL GTH-BLYP-q1
    &END KIND
    &KIND O
      BASIS_SET DZVP-GTH
      POTENTIAL GTH-BLYP-q6
    &END KIND
  &END SUBSYS
&END FORCE_EVAL

&MOTION   
  &GEO_OPT
    OPTIMIZER BFGS
    MAX_DR    3.0E-03
    MAX_FORCE 4.5E-04
    RMS_DR    1.5E-03
    RMS_FORCE 3.0E-04
  &END
  &PRINT
    &RESTART
      BACKUP_COPIES 0
    &END
    &RESTART_HISTORY OFF
    &END  
  &END PRINT
&END MOTION