[CP2K-user] odd force drift convergence with respect to density cutoff

W. Lai wei.... at gmail.com
Thu Mar 18 14:11:36 UTC 2021


Dear CP2k users and developers,

I am seeing odd behavior on how force drift(error) change as we change the 
density cutoff value (from 400 to 1600 Ry), for a model material of 
SiC-6H.  I am using the 7.1 version and I changed the force error ("Sum of 
Atomic Forces") to eV/A.

While it is subjective to consider what is an acceptable value for the 
force error (i.e. 0.01 or 0.001 eV/A), such oscillation really makes it a 
difficult task to choose the appropriate cutoff.

It is worth noting this is a hexagonal cell and force error is primarily on 
the z direction.  Input file is enclosed.

Thanks, Wei

[image: Graph2.png]


&GLOBAL
  PROJECT SiC
  RUN_TYPE ENERGY_FORCE
  PRINT_LEVEL LOW
&END GLOBAL
&FORCE_EVAL
  STRESS_TENSOR ANALYTICAL
  METHOD QS
  &DFT
    BASIS_SET_FILE_NAME  BASIS_MOLOPT
    POTENTIAL_FILE_NAME  GTH_POTENTIALS
    
    &MGRID
      CUTOFF 400
      REL_CUTOFF 60
    &END MGRID

    &QS
      METHOD GPW
      EPS_DEFAULT 1.0E-12
    &END QS
    
    &SCF                              
      SCF_GUESS ATOMIC
      MAX_SCF 100
      EPS_SCF 5.0E-8
      ADDED_MOS 60
      CHOLESKY INVERSE
      &SMEAR ON
        METHOD FERMI_DIRAC
        ELECTRONIC_TEMPERATURE [K] 300
      &END SMEAR
      &DIAGONALIZATION
      &END DIAGONALIZATION
      &MIXING
          METHOD BROYDEN_MIXING
          ALPHA   0.2
      &END      
      &PRINT
        &RESTART OFF
        &END
      &END
    &END SCF
    
    &XC
      &XC_FUNCTIONAL PBE
      &END XC_FUNCTIONAL
    &END XC
    
    &POISSON
       PERIODIC XYZ
    &END

    &PRINT
      &E_DENSITY_CUBE OFF
        &EACH
          MD 10
        &END EACH
        STRIDE 1 1 1             
      &END E_DENSITY_CUBE
    &END PRINT
  &END DFT
  
  &SUBSYS
    &KIND Si
      ELEMENT   Si
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE
    &END KIND
    &KIND C
      ELEMENT   C
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE
    &END KIND    
    &CELL
      PERIODIC XYZ
      A     9.2430000305         0.0000000000         0.0000000000
      B    -4.6215010811         8.0046722182         0.0000000000
      C     0.0000000000         0.0000000000        15.1247997284
    &END CELL

    &COORD
Si 0.0 0.0 0.0
Si -1.5405004 2.6682241 0.0
Si -3.0810008 5.3364482 0.0
Si 3.0810001 0.0 0.0
Si 1.5404997 2.6682241 0.0
Si -7.1525574e-07 5.3364482 0.0
Si 6.1620002 0.0 0.0
Si 4.6215 2.6682241 0.0
Si 3.0809994 5.3364482 0.0
Si 0.0 0.0 7.5623999
Si -1.5405004 2.6682241 7.5623999
Si -3.0810008 5.3364482 7.5623999
Si 3.0810001 0.0 7.5623999
Si 1.5404997 2.6682241 7.5623999
Si -7.1525574e-07 5.3364482 7.5623999
Si 6.1620002 0.0 7.5623999
Si 4.6215 2.6682241 7.5623999
Si 3.0809994 5.3364482 7.5623999
Si -1.1920929e-07 1.7788159 2.5208001
Si -1.5405003 4.4470396 2.5208001
Si -3.0810008 7.1152635 2.5208001
Si 3.0810001 1.7788159 2.5208001
Si 1.5405 4.4470396 2.5208001
Si -4.7683716e-07 7.1152635 2.5208001
Si 6.1619997 1.7788159 2.5208001
Si 4.6215 4.4470396 2.5208001
Si 3.0809994 7.1152635 2.5208001
Si 1.5405 0.889408 10.0832005
Si -4.7683716e-07 3.5576318 10.0832005
Si -1.5405007 6.2258563 10.0832005
Si 4.6215 0.889408 10.0832005
Si 3.0809999 3.5576318 10.0832005
Si 1.5404995 6.2258563 10.0832005
Si 7.7025004 0.889408 10.0832005
Si 6.1620002 3.5576318 10.0832005
Si 4.621501 6.2258563 10.0832005
Si 1.5405001 0.889408 5.0350456
Si -2.3841858e-07 3.5576318 5.0350456
Si -1.5405004 6.2258563 5.0350456
Si 4.6215 0.889408 5.0350456
Si 3.0809999 3.5576318 5.0350456
Si 1.5404995 6.2258563 5.0350456
Si 7.7025004 0.889408 5.0350456
Si 6.1620002 3.5576318 5.0350456
Si 4.621501 6.2258563 5.0350456
Si -2.3841858e-07 1.7788158 12.5974455
Si -1.5405004 4.4470396 12.5974455
Si -3.0810008 7.1152635 12.5974455
Si 3.0810003 1.7788158 12.5974455
Si 1.5405 4.4470396 12.5974455
Si -4.7683716e-07 7.1152635 12.5974455
Si 6.1619997 1.7788158 12.5974455
Si 4.6215 4.4470396 12.5974455
Si 3.0809994 7.1152635 12.5974455
C -1.1920929e-07 1.7788159 0.6231418
C -1.5405003 4.4470396 0.6231418
C -3.0810008 7.1152635 0.6231418
C 3.0810001 1.7788159 0.6231418
C 1.5405 4.4470396 0.6231418
C -4.7683716e-07 7.1152635 0.6231418
C 6.1619997 1.7788159 0.6231418
C 4.6215 4.4470396 0.6231418
C 3.0809994 7.1152635 0.6231418
C 1.5405 0.889408 8.1855412
C -4.7683716e-07 3.5576318 8.1855412
C -1.5405007 6.2258563 8.1855412
C 4.6215 0.889408 8.1855412
C 3.0809999 3.5576318 8.1855412
C 1.5404995 6.2258563 8.1855412
C 7.7025004 0.889408 8.1855412
C 6.1620002 3.5576318 8.1855412
C 4.621501 6.2258563 8.1855412
C 1.5405001 0.889408 3.1459584
C -2.3841858e-07 3.5576318 3.1459584
C -1.5405004 6.2258563 3.1459584
C 4.6215 0.889408 3.1459584
C 3.0809999 3.5576318 3.1459584
C 1.5404995 6.2258563 3.1459584
C 7.7025004 0.889408 3.1459584
C 6.1620002 3.5576318 3.1459584
C 4.621501 6.2258563 3.1459584
C -2.3841858e-07 1.7788158 10.7083578
C -1.5405004 4.4470396 10.7083578
C -3.0810008 7.1152635 10.7083578
C 3.0810003 1.7788158 10.7083578
C 1.5405 4.4470396 10.7083578
C -4.7683716e-07 7.1152635 10.7083578
C 6.1619997 1.7788158 10.7083578
C 4.6215 4.4470396 10.7083578
C 3.0809994 7.1152635 10.7083578
C 0.0 0.0 5.6657501
C -1.5405004 2.6682241 5.6657501
C -3.0810008 5.3364482 5.6657501
C 3.0810001 0.0 5.6657501
C 1.5404997 2.6682241 5.6657501
C -7.1525574e-07 5.3364482 5.6657501
C 6.1620002 0.0 5.6657501
C 4.6215 2.6682241 5.6657501
C 3.0809994 5.3364482 5.6657501
C 0.0 0.0 13.2281494
C -1.5405004 2.6682241 13.2281494
C -3.0810008 5.3364482 13.2281494
C 3.0810001 0.0 13.2281494
C 1.5404997 2.6682241 13.2281494
C -7.1525574e-07 5.3364482 13.2281494
C 6.1620002 0.0 13.2281494
C 4.6215 2.6682241 13.2281494
C 3.0809994 5.3364482 13.2281494
    &END COORD
  &END SUBSYS
  
  &PRINT
    &FORCES ON
    &END FORCES
    &TOTAL_NUMBERS  ON
    &END TOTAL_NUMBERS
  &END PRINT
  
&END FORCE_EVAL

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