[CP2K:5054] Cell Optimization: failed to compare the lattice parameter with XRD data, how to change the setting in input?

[hut... at chem.uzh.ch]

Hi

We just have to guess here.

1) If you say VASP results, do you mean PAW calculations with
   the same functional (especially D3 correction)? Have you
   tested that those calculations are converged with respect to the 
   projector basis, the cutoff (wavefunction and density), etc.
2) DZVP basis sets are a compromise between accuracy and efficiency.
   Maybe for your system a larger basis is needed to get an 
   acceptable accuracy.
3) vdW cutoff of 4 Angstrom is definitely too short, default is 10
   and even that is on the small site.
4) Your convergence criteria for geometry and cell are rather lax.
   For systems with soft modes (like yours) you have to increase the values.
5) I would use the OT optimizer, not diagonalization, with a good preconditioner.
6) Before increasing the Cutoff, I would increase the REL_CUTOFF to 60. 

regards

Juerg Hutter

--------------------------------------------------------------
Juerg Hutter                         Phone : ++41 44 635 4491
Institut für Chemie                  FAX   : ++41 44 635 6838
Universität Zürich                   E-mail: hut... at chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
---------------------------------------------------------------

-----cp... at googlegroups.com wrote: -----
To: cp... at googlegroups.com
From: Jingyun Ye 
Sent by: cp... at googlegroups.com
Date: 03/10/2014 04:17AM
Subject: [CP2K:5054] Cell Optimization: failed to compare the lattice parameter with XRD data, how to change the setting in input?

Hi, all

I met a problem which stops me to further study my system. I am doing the cell optimization of  MOF crystal which is a cubic structure. I always failed to compare my calculated lattice parameter with the experimental data though I try to change the setting in the input, such as increase the cut_off from 300 to 350, increase the EPS in QS to 10-12, in SCF to 10-7. The lattice from my calculation is 0.2 angstrom larger than the XRD data. But my VASP results is close to the experimental data. I also found other calculation result which is also close to the experimental result too. Could you please  give me some suggestions about the setting? Is there any setting I could try to get better data?
I will be very grateful！

&GLOBAL
  PROJECT ....
  RUN_TYPE CELL_OPT
  PRINT_LEVEL MEDIUM
&END GLOBAL
&FORCE_EVAL
  METHOD QS
  STRESS_TENSOR NUMERICAL
  &SUBSYS
    &CELL
      A  14.8340  0.0000   0.0000
      B  7.41698  12.8466  0.0000
      C  7.41698  4.28220  12.1119
    &END CELL
     &TOPOLOGY
      COORD_FILE_NAME ......
      COORD_FILE_FORMAT XYZ
      CONNECTIVITY OFF
    &END TOPOLOGY
    &KIND C
      BASIS_SET DZVP-MOLOPT-SR-GTH-q4
      POTENTIAL GTH-PBE-q4
    &END KIND
    &KIND H
      BASIS_SET DZVP-MOLOPT-SR-GTH-q1
      POTENTIAL GTH-PBE-q1
    &END KIND
    &KIND O
      BASIS_SET DZVP-MOLOPT-SR-GTH-q6
      POTENTIAL GTH-PBE-q6
    &END KIND
    &KIND Zr
      BASIS_SET DZVP-MOLOPT-SR-GTH-q12
      POTENTIAL GTH-PBE-q12 
    &END KIND
  &END SUBSYS
  &DFT
    BASIS_SET_FILE_NAME ~/input/cp2k/cp2k-2.4.0/tests/QS/BASIS_MOLOPT
    POTENTIAL_FILE_NAME ~/input/cp2k/cp2k-2.4.0/tests/QS/GTH_POTENTIALS
    &QS
      EPS_DEFAULT 1.0E-12
    &END QS
    &MGRID
      CUTOFF 300
      NGRIDS 4
      REL_CUTOFF 40
    &END MGRID
    &SCF
      SCF_GUESS RESTART
      EPS_SCF 1.0E-07
      MAX_SCF 1000
      &DIAGONALIZATION T
        ALGORITHM STANDARD
      &END DIAGONALIZATION
      &MIXING T
        ALPHA 0.5
        METHOD PULAY_MIXING
        NPULAY 5
      &END MIXING
      &PRINT
        &RESTART OFF
        &END RESTART
      &END PRINT
    &END SCF
    &XC
      &XC_FUNCTIONAL PBE 
      &END XC_FUNCTIONAL
         &VDW_POTENTIAL
           DISPERSION_FUNCTIONAL PAIR_POTENTIAL
             &PAIR_POTENTIAL
              TYPE DFTD3
              REFERENCE_FUNCTIONAL PBE
              PARAMETER_FILE_NAME ./dftd3.dat
              R_CUTOFF 4.0
             &END PAIR_POTENTIAL
          &END VDW_POTENTIAL
    &END XC
  &END DFT
&END FORCE_EVAL
&MOTION
  &CELL_OPT
    EXTERNAL_PRESSURE 1.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 1.0
    KEEP_ANGLES TRUE     
    MAX_DR    1.0E-03
    MAX_FORCE 1.0E-03
    RMS_DR    1.0E-03    
    RMS_FORCE 1.0E-03
    MAX_ITER 1000
    OPTIMIZER CG
      &CG
        MAX_STEEP_STEPS  1000
      &END CG
    PRESSURE_TOLERANCE 0.1    
      &PRINT
        &CELL ON
          FILENAME ./cell.dcd
        &END CELL
      &END PRINT
  &END CELL_OPT
  &GEO_OPT 
    TYPE MINIMIZATION
    MAX_DR    1.0E-03
    MAX_FORCE 1.0E-03
    RMS_DR    1.0E-03
    RMS_FORCE 1.0E-03
    MAX_ITER 200
    OPTIMIZER CG
    &CG
      MAX_STEEP_STEPS  0
      RESTART_LIMIT 9.0E-01
    &END CG
   &END GEO_OPT
  &PRINT
     &CELL HIGH
     &END CELL
     &STRUCTURE_DATA ON
     &END STRUCTURE_DATA
   &END PRINT
&END MOTION  

  
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