Dear Ashutosh,
> To run the constant pressure MD I used ntb=2,ntp=1,and taup=2 but when
> plotted the graph for pressure it is varying large .Sometimes its going
> negative what does this imply.
This is perfectly normal. The instantaneous pressure will always fluctuate
by large amounts. Negative pressures are also reasonable, they just imply
that the box size needs to shrink slightly. Note with taup=2.0 this implies
a 2ps relaxation time so the pressure will not be instantly readjusted to
1.0 on every step but instead will be adjusted such that it would reach this
value after 2ps.
Try looking at the average pressure. This should be close to 1.0.
Also look at the density vs time, this will give you a more relevant plot to
whether things are stable.
All the best
Ross
/\
\/
|\oss Walker
| Assistant Research Professor |
| San Diego Supercomputer Center |
| Tel: +1 858 822 0854 | EMail:- ross.rosswalker.co.uk |
|
http://www.rosswalker.co.uk |
http://www.wmd-lab.org/ |
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Received on Wed May 12 2010 - 07:30:05 PDT
