Constant presure MD

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widom · #1 Post by **widom** » Mon Nov 28, 2005 8:56 pm

Has anyone worked on constant pressure MD? This could be very handy for simulations of liquid alloys where the atomic volume is rairly known from experiment.

If there is currently no facility for a constant pressure simulation, is there some way to extract the pressure from a simulation? I believe the pressure reported by VASP is related to a derivative of energy with respect to volume, while at finite temperature a derivative of FREE energy is needed.

Thanks in advance for any suggestions.

#2 Post by **admin** » Wed Dec 07, 2005 4:54 pm

1) the current vasp release does not include a possibility of NPT-MD
simulations
2) the external pressure for a given configuration (V, ionic positions)
can be read from the OUTCAR file if ISIF is set in INCAR:
please search for the string external pressure
-- ISIF=1 total pressure (only the trace of the force tensor is considered)
-- ISIF > 1 the individual components of the stress tensor are reliable as well.
please have a look into the online handbook about the possible choices of ISIF,
http://cms.mpi.univie.ac.at/vasp/vasp/node103.html
As the pressure is calculated via the stress tensors, the precision of the run has to be increased (set PREC=High) to obtain reliable values.

ssim · #3 Post by **ssim** » Mon Mar 30, 2009 7:49 am

Having read the release notes for version 5.2, I assume that still "current vasp release [now at 5.2] does not include a possibility of NPT-MD simulations." Are there any plans to implement this feature in a future version?