[CP2K-user] [CP2K:13693] Wrong density prediction in NpT AIMD

[Abedi, Mostafa]

Dear Juerg and Thomas,

Thank you so much for your helpful suggestions. I will try to modify my
input file accordingly and repeat the calculation.

Best,
Mostafa

On Wed, Jul 29, 2020 at 10:07 AM Thomas Kühne <tku... at gmail.com> wrote:

> Dear Mostafa,
>
> your simulation is way too short. Equilibrating the density needs many
> dozens of ps of simulation,
> and much more so since you are using the default 1ps time constant for the
> barostat. My
> suggestion is to reduce that to 100 fs and rerun your simulation for at
> least 25 ps. Also, you were
> missing to add the VdW contribution of the wB97X XC functional.
>
> Cheers,
> Thomas
>
> Am 29.07.2020 um 14:57 schrieb Abedi, Mostafa <mostaf... at brown.edu>:
>
> Hi Everyone,
> I've performed NpT AIMD simulations for a system containing 8 CH4
> molecules. The system was equilibrated using 2 ps NVT (300K) followed by 2
> ps NVE. For some reason, the predicted density keeps decreasing and getting
> away from the correct value (The correct density is 0.232 g/cm3):
>
> *    Time evaluation of density for a box of 8 CH4 at 300 K and 400 bar*
> <density.PNG>
> The wB97XD/TZVP-MOLOPT-GTH level of theory was used for the electronic
> structure part. Unfortunately, there is not much in the literature for this
> system (or similar systems) to get some ideas for the level of theory. To
> my mind, it could be due to the wrong prediction of the intermolecular
> repulsive interactions (vdW dispersion forces). But, there might be some
> other parameters in the simulations that can cause this issue. Any
> suggestions or advice for fixing this issue would be greatly appreciated.
> Many thanks.
>
> Best,
> Mostafa
>
> Input file:
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> *&GLOBAL  PROJECT methane  RUN_TYPE MD     WALLTIME 10000000  IOLEVEL  LOW
>          &END GLOBAL*
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> *&FORCE_EVAL STRESS_TENSOR ANALYTICAL  METHOD Quickstep  &DFT
> BASIS_SET_FILE_NAME BASIS_MOLOPT    POTENTIAL_FILE_NAME GTH_POTENTIALS
>             CHARGE 0    MULTIPLICITY 1    &MGRID       CUTOFF [Ry] 400
> &END    &QS       METHOD GPW        EPS_DEFAULT 1.0E-10
>  EXTRAPOLATION ASPC     &END    &POISSON       PERIODIC XYZ
>  POISSON_SOLVER PERIODIC    &END    &SCF        &PRINT        &RESTART OFF
>       &END      &END               SCF_GUESS ATOMIC       MAX_SCF 300
> EPS_SCF 1.0E-6       &OT        PRECONDITIONER FULL_SINGLE_INVERSE
> MINIMIZER CG      &END OT      &OUTER_SCF         MAX_SCF 300
> EPS_SCF 1.0E-6       &END    &END SCF    &XC      &XC_FUNCTIONAL
> &LIBXC          FUNCTIONAL XC_HYB_GGA_XC_WB97X_D        &END LIBXC
> &END XC_FUNCTIONAL    &END XC  &END DFT  &SUBSYS    &CELL       ABC
> [angstrom] 9.71 9.71 9.71      PERIODIC XYZ    &END CELL    &TOPOLOGY
> COORD_FILE_NAME methane.xyz <http://methane.xyz/>      COORD_FILE_FORMAT
> XYZ    &END    &KIND H      ELEMENT H      BASIS_SET TZVP-MOLOPT-GTH
> POTENTIAL GTH-PBE-q1    &END KIND    &KIND C      ELEMENT C      BASIS_SET
> TZVP-MOLOPT-GTH      POTENTIAL GTH-PBE-q4    &END KIND  &END SUBSYS
> &PRINT    &FORCES ON     FILENAME forces     &END  &END&END
> FORCE_EVAL&MOTION &GEO_OPT   OPTIMIZER BFGS    MAX_ITER  1000   MAX_DR
>  [bohr] 0.003    &BFGS   &END &END  &MD   ENSEMBLE NPT_I   STEPS 15000
>  TIMESTEP 0.5   TEMPERATURE 300   &BAROSTAT    PRESSURE 400   &END
> BAROSTAT   &THERMOSTAT    REGION MASSIVE    TYPE CSVR    &CSVR    TIMECON
> 50    &END CSVR   &END THERMOSTAT &END MD &PRINT   &TRAJECTORY    FORMAT
> XYZ    &END   &CELL    FILENAME cell    &END &END&END MOTION*
>
>
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> .
>
>
>
>
> ==============================
> Thomas D. Kühne
> Dynamics of Condensed Matter
> Chair of Theoretical Chemistry
> University of Paderborn
> Warburger Str. 100
> D-33098 Paderborn
> Germany
> tdku... at mail.upb.de
> +49/(0)5251/60-5726
>
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