BOMD - Total energy increasing

[Axel]

On Friday, July 1, 2011 4:42:40 AM UTC-4, sandeep wrote:
>
> Dear all,
>               I am doing an BOMD run of carboxylic acid in water. After 
> 6ps, i plotted conserved quantity as a function of step no.  which shows 
> total energy is increasing.  Can anybody help
> why it is increasing ?
>

half a femtosecond is a pretty aggressive timestep
for a system with non-deuterated hydrogens.

it is a fundamental property of MD simulations
that they don't conserve energy, if you time step 
is too large.

axel.

 

>
> Input file :
>
> &FORCE_EVAL
>   METHOD Quickstep
>   &DFT
>     BASIS_SET_FILE_NAME BASIS_MOLOPT
>     POTENTIAL_FILE_NAME POTENTIAL
>     CHARGE = 0  
>     &MGRID
>       CUTOFF 280
>       NGRIDS 5 
>       REL_CUTOFF 40
>     &END MGRID
>      &QS
>        METHOD GPW
>        EPS_DEFAULT 1.0E-10
>      &END QS
>      &SCF
>        SCF_GUESS ATOMIC 
>        EPS_SCF 1.0E-6
>        MAX_SCF 150
> #       MIXING 0.3
>        &OUTER_SCF
>           EPS_SCF 1.0E-6
>           MAX_SCF 50
>        &END
>     &OT
>           MINIMIZER CG
>           PRECONDITIONER FULL_ALL
>           ENERGY_GAP 0.001
>           STEPSIZE 0.05
>        &END
>  
>     &END SCF
>     &XC
>      &XC_FUNCTIONAL BLYP 
>       &END XC_FUNCTIONAL
>       &vdW_POTENTIAL
>          DISPERSION_FUNCTIONAL PAIR_POTENTIAL
>          &PAIR_POTENTIAL
>             TYPE DFTD2
>             REFERENCE_FUNCTIONAL BLYP 
>          &END PAIR_POTENTIAL
>       &END vdW_POTENTIAL
>  
>    &END XC
>   &END DFT
>
>   &SUBSYS
>     &CELL 
>       ABC 12.16174 12.16174 12.16174
>     &END CELL
>
>     &COORD
>      @INCLUDE coor.xyz 
>     &END COORD
>
>      &KIND O
>       BASIS_SET TZV2P-MOLOPT-GTH-q6 
>       POTENTIAL GTH-BLYP-q6
>     &END KIND
>     
>     &KIND C
>       BASIS_SET TZV2P-MOLOPT-GTH-q4 
>       POTENTIAL GTH-BLYP-q4
>     &END KIND
>
>     &KIND H
>       BASIS_SET TZV2P-MOLOPT-GTH-q1 
>       POTENTIAL GTH-BLYP-q1
>       MASS 1.00794
>     &END KIND
>
>   &END SUBSYS
> &END FORCE_EVAL
>
> &GLOBAL
>   PROJECT OUT-URACIL-MD
>   RUN_TYPE MD
>   PRINT_LEVEL MEDIUM
> &END GLOBAL
>
> &MOTION
>   &MD
>     ENSEMBLE NVT
>     STEPS 100000
>     TIMESTEP 0.5
>     &THERMOSTAT
>       &NOSE
>         LENGTH 3
>         YOSHIDA 3
>         TIMECON 100.0
>         MTS 2
>       &END NOSE
>     &END THERMOSTAT
>   TEMPERATURE 298.15
>   &END MD
> &END MOTION
>
>
> ----
>
>
> Thanks & Regards,
> Sandeep kumar Reddy
> Ph. D. student
>
>
>
>
>
>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20110701/fd98d7eb/attachment.htm>