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["P. Ganesh" <pganesh@ciw.edu>]

Thanks.  I did try several values of the set of variables to reduce the discontinuity at restart, but the periodic oscillation in pressure is always there, with the period  naturally depending on the mass of the barostat.  I just wonder if I should expect such a periodic oscillation in energy as well, since I don't see that in papers or books on constant pressure simulation.   The size of the oscillations reduces as the starting volume (in the input file) is set close to the true equilibrium volume at that pressure.

Thank you again.

PG


Anglade Pierre-Matthieu wrote:

c65e87810906152204r6ce0b791h485d4eeec614fffa@mail.gmail.com" type="cite">

Hi,

I fear I can't help with the first part of your question. Yet I must
underline that it is natural that the pressure has periodic
oscillation, and that on restart you get discontinuities. This is
because, your system is coupled with an "arbitrary" barostat to keep
pressure ALMOST constant. To reduce the oscillation, you have to guess
optimal values for dtion, nnos, qmass, vmass that fit your system.

regards

PMA

On Tue, Jun 16, 2009 at 3:42 AM, Ganesh Panchapakesan<gpanchap@gmail.com> wrote:
  

Hi All,

Does anyone have any experience with the constant pressure MD (ionmov=13
using the Martyna et.al. Mol. Phys. 1996, p1117 algorithm)  or know of any
paper that uses that part of the code?  If so, I would like to know the
parameters (dtion, nnos, qmass, vmass and bmass) they chose for their
system  and the system they studied. I am aware of the sample input file for
Al, but it seems to be having periodic oscillations in pressure, and with
restart shows strong discontinuities in pressure and energy.

Thanks,
PG




    

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