DD-CAM in CP2k

[Michele Loriso]

Dear CP2k community, 

our team is currently performing geometry optimizations and single points on several zinc(II) bulks, and using v. 10.0.

While attempting to run geo_opts and wfn_opts using a DD-CAM functional (reported below the input file), we obtained an absurd value for the HOMO-LUMO gap (ca. 9 eV) of ZnO.

May I ask you for an advice in assemblying the input file?

Thanks in advance!

&XC
 &XC_FUNCTIONAL
        &HYB_GGA_XC_CAM_PBEH
          SCALE 0.0         
          _OMEGA 0.75          ! Range-separation parameter (in Bohr⁻¹)
          _ALPHA 1.0           ! Short-range HF exchange
          _BETA 0.20           ! Long-range HF exchange
        &END HYB_GGA_XC_CAM_PBEH
 &END XC_FUNCTIONAL
&HF
&SCREENING
EPS_SCHWARZ 1.0E-6
SCREEN_ON_INITIAL_P FALSE
&END SCREENING
&INTERACTION_POTENTIAL
POTENTIAL_TYPE TRUNCATED
CUTOFF_RADIUS 5.5
T_C_G_DATA  /g100_work/IscrC_MHP-DEF/t_c_g.dat
&END INTERACTION_POTENTIAL
&MEMORY
MAX_MEMORY 3600
EPS_STORAGE_SCALING 0.1
&END MEMORY

&END HF
    &END XC

[Frederick Stein]

Dear Michele,

Because you are interested in a range-separated hybrid functional, you have to setup the HF section accordingly (CP2K does not do that automatically, see https://www.cp2k.org/_media/events:2019_ghent:admm.pdf or https://github.com/cp2k/cp2k/tree/master/data/xc_section for more inspiration). Beware that you need to convert the short-range/long-range-split to a Coulomb/long-range split. Your HF section should look as follows

&HF

&INTERACTION_POTENTIAL

POTENTIAL_TYPE MIXED_CL_TRUNC

OMEGA 0.75

# the same as the amount of HF short-range exchange

SCALE_COULOMB 1.0

# the same as the amount of long-range MINUS the amount of short-range exchange

SCALE_LONGRANGE -0.8

# A bit less than half of the distance to the nearest neighbor

CUTOFF_RADIUS 5.5
T_C_G_DATA  /g100_work/IscrC_MHP-DEF/t_c_g.dat

&END

<your other options>

&END HF

HTH,

Frederick

[Michele Loriso]

Dear Frederick, many thanks for your quick answer! 
Following your suggestion, we modified our input file as reported below and obtained a 0.09 eV for the HOMO-LUMO gap. 

For the sake of completeness, we already obtained an HOMO-LUMO gap of 2.77 eV using a KPBE functional, and we were expecting 
a value close to 3.4 eV (as reported in this work: https://www.nature.com/articles/s41524-023-01064-x/tables/2).

!&END EXT_RESTART
&FORCE_EVAL
  METHOD         Quickstep
!  STRESS_TENSOR  ANALYTICAL
!  &PRINT
!    &STRESS_TENSOR
!    &END STRESS_TENSOR
!  &END PRINT
  &DFT
            BASIS_SET_FILE_NAME /g100_work/IscrC_MHP-DEF/BASIS/BASIS_MOLOPT.txt
            POTENTIAL_FILE_NAME /g100_work/IscrC_MHP-DEF/BASIS/GTH_POTENTIALS.txt
            BASIS_SET_FILE_NAME /g100_work/IscrC_MHP-DEF/BASIS/BASIS_ADMM_MOLOPT.txt
            BASIS_SET_FILE_NAME /g100_work/IscrC_MHP-DEF/BASIS/BASIS_ADMM.txt
            WFN_RESTART_FILE_NAME ./ZnO-KPBE-RESTART.wfn
!   CHARGE -1
!    UKS T
    &MGRID
      CUTOFF       600
      REL_CUTOFF    60
    &END MGRID
    &QS
    &END QS
    &SCF
      SCF_GUESS  RESTART
      MAX_SCF    50
      &OT
        MINIMIZER       CG
        PRECONDITIONER  FULL_SINGLE_INVERSE
      &END
      &OUTER_SCF
        MAX_SCF  50
      &END
!      &PRINT
!        &RESTART OFF
!        &END
!      &END
    &END SCF
    &AUXILIARY_DENSITY_MATRIX_METHOD
        METHOD BASIS_PROJECTION
        ADMM_PURIFICATION_METHOD MO_DIAG
     &END AUXILIARY_DENSITY_MATRIX_METHOD
    &PRINT
!       &MO LOW
!          EIGENVALUES
!          &EACH
!              QS_SCF 0
!          &END EACH
!       &END MO
       &MO_CUBES
        NHOMO 1
       NLUMO 1
!        WRITE_CUBE
!         &EACH
!          MD 50
!         &END EACH
      &END MO_CUBES
!       &TOT_DENSITY_CUBE
!       &END
    &END PRINT
&XC
&XC_FUNCTIONAL
        &HYB_GGA_XC_CAM_PBEH

          _OMEGA 0.75          ! Range-separation parameter (in Bohr⁻¹)

          _ALPHA 1.00           ! Short-range HF exchange

          _BETA  0.20           ! Long-range HF exchange
        &END HYB_GGA_XC_CAM_PBEH
 &END XC_FUNCTIONAL
&HF
&SCREENING
EPS_SCHWARZ 1.0E-6
SCREEN_ON_INITIAL_P FALSE
&END SCREENING
&INTERACTION_POTENTIAL

POTENTIAL_TYPE MIX_CL_TRUNC
OMEGA 0.75
CUTOFF_RADIUS 5.5
SCALE_COULOMB  1.00
SCALE_LONGRANGE -0.80

T_C_G_DATA  /g100_work/IscrC_MHP-DEF/t_c_g.dat
&END INTERACTION_POTENTIAL
&MEMORY
MAX_MEMORY 3600
EPS_STORAGE_SCALING 0.1
&END MEMORY

FRACTION 1.0
&END HF
    &END XC
  &END DFT
  &SUBSYS
    &CELL
      ABC  12.880 12.880 15.600
      ALPHA_BETA_GAMMA 90.0 90.0 120.0
    &END CELL
    &TOPOLOGY
      COORD_FILE_NAME  ./ZnO-opt.xyz
      COORD_FILE_FORMAT xyz
    &END TOPOLOGY
    &KIND Zn
      BASIS_SET DZVP-MOLOPT-SR-GTH-q12
      BASIS_SET AUX_FIT cFIT9
      POTENTIAL GTH-PBE-q12
    &END KIND
    &KIND O
      BASIS_SET DZVP-MOLOPT-SR-GTH-q6
      BASIS_SET AUX_FIT cFIT3
      POTENTIAL GTH-PBE-q6
    &END KIND
  &END SUBSYS
&END FORCE_EVAL
&MOTION
! &MD
!    STEPS        50000000
!    TIMESTEP     1.00
!    TEMPERATURE  300
!    ENSEMBLE     NVT
!    &THERMOSTAT
!      REGION MASSIVE
!      TYPE NOSE
!      &NOSE
!        TIMECON  16.68
!      &END NOSE
!    &END THERMOSTAT
!    &BAROSTAT
!      PRESSURE  0.0
!      TIMECON   300
!    &END BAROSTAT
!  &END MD
!  &PRINT
!   &TRAJECTORY
!     &EACH
!       MD 1
!     &END EACH
!   &END TRAJECTORY
!   &CELL
!     &EACH
!       MD 1
!     &END EACH
!   &END CELL
!   &VELOCITIES OFF
!   &END VELOCITIES
!   &FORCES OFF
!   &END FORCES
!   &RESTART_HISTORY
!     &EACH
!       MD 500
!     &END EACH
!   &END RESTART_HISTORY
!   &RESTART
!     BACKUP_COPIES 3
!     &EACH
!       MD 1
!     &END EACH
!   &END RESTART
!  &END PRINT
&GEO_OPT
  OPTIMIZER BFGS
    &BFGS
     TRUST_RADIUS 0.1
    &END
&END GEO_OPT
&END MOTION
&GLOBAL
  PROJECT      ZnO-DDCAM
  RUN_TYPE     WFN_OPT
  PRINT_LEVEL  LOW
&END GLOBAL

[Frederick Stein]

Dear Michele,

You use pseudopotentials optimized for PBE but you need pseudopotentials optimized for hybrid functionals. If there are none in the files you provide to CP2K, check out POTENTIAL_UZH in the data directory.

Best,

Frederick