Francesco
I think I figured out the problem. For <64 beads, the temperature of the
system is tightly regulated when there is a change in temperature, for
example starting with 0.1K (tempi=0.1 or restarting from a 0.1K simulation)
and ending with 5K (temp0=5K).
However for 64 beads and more, the temperature oscillates widely if the
restart and target temperatures are not close.
Andrew
On Sat, Aug 13, 2011 at 7:07 PM, Francesco Paesani <fpaesani.ucsd.edu>wrote:
> Hi Andrew,
>
> I believe that it is normal. You need to find the right parameters for
> running NMPIMD with the number of beads that you need. It is quite possible
> that a timestep of 0.00001 is not enough. Everything depends on the
> interactions, atom masses, temperature and number of beads. Please look at
> the references about PIMD in general to see how the frequencies of the
> springs that connect the beads depends on these quantities. From that
> analysis you should be able to determine the right timestep for your
> simulations.
>
> Best wishes,
> Francesco
>
> ----------------------------------------------------------------------
> Francesco Paesani, Ph.D.
> Assistant Professor
>
> Department of Chemistry & Biochemistry
> University of California, San Diego
> Urey Hall 3242
> 9500 Gilman Drive #0314
> La Jolla, CA 92093-0314
> phone: (858) 822 - 3383
> email: fpaesani.ucsd.edu
> web: http://paesanigroup.ucsd.edu
> ----------------------------------------------------------------------
>
>
>
>
>
>
> On Aug 13, 2011, at 8:11 AM, Andrew Petersen wrote:
>
> > Hello users,
> >
> > Im running nmpimd for a small system. 4,8,16,32 beads works fine. But
> > 64beads, there is slow heating. With 128beads the heating is rapid and
> the
> > simulation crashes. Reducing the step size from dt=0.0001 to 0.00001
> does
> > not help. I would appreciate any help I can get to fix this.
> >
> > Regards
> > Andrew
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Received on Tue Aug 23 2011 - 07:30:02 PDT
