[CP2K:4552] Bulk modulus of silicon with CP2K

leila salimi leila... at gmail.com
Tue Aug 13 13:37:16 UTC 2013
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Hi Juerg,

Thanks very much. I tried without dispersion correction for DZVP basis
set, CUTOFF 500 and REL_CUTOFF 80. I got better results( B = 90 GPa).
I didn't understand how I can find my calculation is converged or not?
For k-points you mean the system of 64 atoms is not big enough and I have
to check with small unit cell (8 atoms) and then with MULTIPLE_UNIT_CELL
keyword increase the size of  the system and to see how it is converged?

Regards,
Leila



On Mon, Aug 12, 2013 at 3:17 PM, <hut... at pci.uzh.ch> wrote:

> Hi
>
> I would guess that your calculation is not yet converged
> with respect to
>
> 1) the basis set
> 2) the k-points. I would use a small unit cell and then
>    the MULTIPLE_UNIT_CELL keyword to check for convergence
> 3) the cutoff, you are probably close here (REL_CUTOFF 80, just to be sure)
>    I would still use the REF_CELL keyword in order to do constant
>    number of grid point calculations
> 4) the dispersion correction will change the reference PBE value
>
> regards
>
> Juerg
>
>
> --------------------------------------------------------------
> Juerg Hutter                         Phone : ++41 44 635 4491
> Physical Chemistry Institute   FAX   : ++41 44 635 6838
> University of Zurich               E-mail:  hut... at pci.uzh.ch
> Winterthurerstrasse 190
> CH-8057 Zurich, Switzerland
> ---------------------------------------------------------------
>
> -----cp... at googlegroups.com wrote: -----
> To: cp... at googlegroups.com
> From: leila salimi
> Sent by: cp... at googlegroups.com
> Date: 08/12/2013 03:05PM
> Subject: Re: [CP2K:4550] Bulk modulus of silicon with CP2K
>
> Dear Juerg,
>
> Thanks for your answer.
> 1) the PBE value for B is 89 GPa.
> 2) I also tried with higher cutoff and REF_CUTOFF, but it didn't change.
>
>
> &MGRID
>       NGRIDS 8
>       CUTOFF 500
>       REL_CUTOFF  60
>     &END MGRID
>
>
> On Mon, Aug 12, 2013 at 2:40 PM,  <hut... at pci.uzh.ch> wrote:
>  Hi
>
>  two things to do:
>  1) What is the official PBE value for this quantity?
>  2) Use a REF_CELL and a high enough cutoff (has to be tested)
>     in order to get a smooth enough pressure curve
>
>  regards
>
>  Juerg
>
>  --------------------------------------------------------------
>  Juerg Hutter                         Phone : ++41 44 635 4491
>  Physical Chemistry Institute   FAX   : ++41 44 635 6838
>  University of Zurich               E-mail:  hut... at pci.uzh.ch
>  Winterthurerstrasse 190
>  CH-8057 Zurich, Switzerland
>  ---------------------------------------------------------------
>
>  -----cp... at googlegroups.com wrote: -----
>  To: cp... at googlegroups.com
>  From: leila
>  Sent by: cp... at googlegroups.com
>  Date: 08/12/2013 11:57AM
>  Subject: [CP2K:4549] Bulk modulus of silicon with CP2K
>
>
>  Hi all,
>
>  I simulated the silicon with 64 atoms and calculated the energy-volume
> plot and fitted with murnaghan.
>  I found the lattice parameter 5.48 A ( lattice parameter in experiment is
> 5.44 A), That is OK but the bulk modulus is 63 GPa that is very low. (B_exp
> = 100 GPa)
>  I really don' t know why cp2k gets B so low???
>
>  I tried with DZVP basis set and PBE functional with 280 Ryd cut off for
> density.
>  I also checked with TZVP, it is not changing so much. It is 66 GPa.
>  Can anybody help me with that?
>  You can find my inputfile in below.
>
>  &GLOBAL
>    PROJECT si64-10.88A
>    PRINT_LEVEL LOW
>    RUN_TYPE GEO_OPT
>  &END GLOBAL
>  &MOTION
>    &CELL_OPT
>      TYPE GEO_OPT
>      OPTIMIZER CG
>      MAX_ITER 20
>      EXTERNAL_PRESSURE [bar] 1.0
>      MAX_DR 0.02
>      RMS_DR 0.01
>      MAX_FORCE 0.0002
>      RMS_FORCE 0.0001
>      KEEP_ANGLES
>      &CG
>        &LINE_SEARCH
>          TYPE 2PNT
>          &2PNT
>          &END
>        &END
>      &END
>    &END
>    &GEO_OPT
>      MAX_ITER 200
>      MINIMIZER BFGS
>    &END
>    &PRINT
>      &STRESS
>      &END STRESS
>      &RESTART
>        &EACH
>          CELL_OPT 1
>        &END
>      &END
>    &END
>  &END
>  &FORCE_EVAL
>    METHOD QS
>    STRESS_TENSOR ANALYTICAL
>    &DFT
>      BASIS_SET_FILE_NAME ./BASIS_MOLOPT
>      POTENTIAL_FILE_NAME ./GTH_POTENTIALS
>      &MGRID
>        CUTOFF 280
>      &END MGRID
>      &QS
>        METHOD GPW
>      &END QS
>      &SCF
>        SCF_GUESS RESTART
>        MAX_SCF 20
>        EPS_SCF 1.0e-5
>        &OUTER_SCF
>        EPS_SCF 1.0E-5
>        &END
>        &OT ON
>  #        MINIMIZER DIIS
>           ROTATION
>        &END OT
>        &PRINT
>          &RESTART
>            BACKUP_COPIES 0
>          &END RESTART
>        &END PRINT
>      &END SCF
>      &XC
>        &XC_FUNCTIONAL PBE
>        &END XC_FUNCTIONAL
>        &vdW_POTENTIAL
>           DISPERSION_FUNCTIONAL PAIR_POTENTIAL
>           &PAIR_POTENTIAL
>              TYPE DFTD3
>              CALCULATE_C9_TERM .TRUE.
>              REFERENCE_C9_TERM .TRUE.
>              LONG_RANGE_CORRECTION .TRUE.
>              PARAMETER_FILE_NAME ./dftd3.dat
>              REFERENCE_FUNCTIONAL PBE
>              R_CUTOFF 8.
>              EPS_CN 0.01
>           &END PAIR_POTENTIAL
>        &END vdW_POTENTIAL
>      &END XC
>    &END DFT
>    &SUBSYS
>      &TOPOLOGY
>        COORD_FILE_NAME ./GEOMETRY.xyz
>        COORDINATE XYZ
>  #      CONNECTIVITY OFF
>      &END TOPOLOGY
>      &KIND Si
>        BASIS_SET DZVP-MOLOPT-SR-GTH
>  #      BASIS_SET SZV-MOLOPT-SR-GTH
>  #       BASIS_SET TZVP-MOLOPT-GTH
>        POTENTIAL GTH-PBE-q4
>      &END
>      &CELL
>        ABC    10.88  10.88 10.88
>      &END
>    &END SUBSYS
>   &END
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