Convergence of W-BCC

[Marcelo Albuquerque]

Dear all,

I'm trying to obtain the converged k-point grid (MONKHORST-PACK scheme) of the alpha phase of W (BCC structure).

Beforehand, I converged both the CUTOFF and REL_CUTOFF. However, when it comes to the K-POINT mesh, I'm getting the same Total Energy for each NxNxN points, where N runs from 3 to 20.

Does someone know what is going on here? I really appreciate any help to understand this issue.

Here are the xyz file and my cp2k input.

2
# File generated with Atomsk by malbuquerque on 2023-07-22 22:14:26
W  0.00000000  0.00000000  0.00000000
W  1.60206186  1.60206186  1.60206186

&GLOBAL
  PROJECT ALPHA_W
  RUN_TYPE ENERGY
  PRINT_LEVEL MEDIUM
&END GLOBAL
&FORCE_EVAL
  METHOD Quickstep
  &DFT
    BASIS_SET_FILE_NAME BASIS_MOLOPT
    POTENTIAL_FILE_NAME GTH_POTENTIALS
    &MGRID
      CUTOFF 600
      REL_CUTOFF 60
    &END MGRID
    &KPOINTS
       SCHEME MONKHORST-PACK 20 20 20
    &END KPOINTS
    &QS
      EPS_DEFAULT 1.0E-12
    &END QS
    &SCF
      SCF_GUESS ATOMIC
      EPS_SCF 1.0E-8
      MAX_SCF 1
      ADDED_MOS 50
      CHOLESKY INVERSE
      &SMEAR ON
        METHOD FERMI_DIRAC
        ELECTRONIC_TEMPERATURE [K] 300
      &END SMEAR
      &DIAGONALIZATION
        ALGORITHM STANDARD
      &END DIAGONALIZATION
      &MIXING
        METHOD BROYDEN_MIXING
        ALPHA 0.4
        BETA 0.5
        NBROYDEN 8
      &END MIXING
    &END SCF
    &XC
      &XC_FUNCTIONAL PBE
      &END XC_FUNCTIONAL
      &VDW_POTENTIAL
        POTENTIAL_TYPE PAIR_POTENTIAL
        &PAIR_POTENTIAL
          TYPE DFTD3
          REFERENCE_FUNCTIONAL PBE
          PARAMETER_FILE_NAME /home/malbuquerque/packages/cp2k-2023.1/data/dftd3.dat
        &END PAIR_POTENTIAL
      &END VDW_POTENTIAL
    &END XC
  &END DFT
  &SUBSYS
    &KIND W
      ELEMENT W
      BASIS_SET DZVP-MOLOPT-SR-GTH-q14
      POTENTIAL GTH-PBE-q14
    &END KIND
    &CELL
      SYMMETRY CUBIC
      A     3.20412372        0.00000000        0.00000000
      B     0.00000000        3.20412372        0.00000000
      C     0.00000000        0.00000000        3.20412372
    &END CELL
    &TOPOLOGY
       COORD_FILE_FORMAT XYZ
       COORD_FILE_NAME alpha_bcc_W_cl2.xyz
       CONN_FILE_FORMAT OFF
    &END TOPOLOGY
  &END SUBSYS
  &PRINT
    &TOTAL_NUMBERS  ON
    &END TOTAL_NUMBERS
  &END PRINT
&END FORCE_EVAL

Best regards,

Marcelo Albuquerque

[fabia...@gmail.com]

Dear Marcelo,

you limit the number of iterations to 1 with "MAX_SCF 1". SCF needs to be properly converged before you can draw any conclusion about cutoff, rel_cutorr, or k-point convergence.

Cheers,

Fabian

[Marcelo Albuquerque]

Dear Fabian,

Thank you for your clarification. 

In fact, you're right. Not only that, other things should be defined in the input. 

After sniffing around the internet, I realized that the following keywords were missing: STRESS_TENSOR (&FORC_EVAL), as you said, MAX_SCF (&DFT -> &SCF), and PERIODIC XYZ (&SUBSYS -> &CELL).

I have fixed my input, and now it is working :D

Cheers,

Marcelo

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