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 Sat Aug 13 2011 - 16:30:03 PDT
