Re: Constant pressure contril

From: Juan Alfredo Freites (
Date: Sat Feb 28 2004 - 20:18:51 CST

On Sat, 28 Feb 2004, Sichun Yang wrote:

> Thank you for your explanation, Jerome.
> However, How can I understand a negative GPRESSURE?

The usual convention for the diagonal elements of the pressure tensor is
positive for compression. If you're simulating a bulk system, i.e.
if you're in hydrostatic conditions you want to get the scalar pressure which is
one third of the trace of the pressure tensor. In a constant pressure
simulations, the average of that quantity should give you back the
requested value.
Make sure that you check here

to understand the difference between namd's group and atomic pressure
tensor calculations and their partial cumulated averages PRESSAVG and

J. Alfredo Freites
Department of Physics
University of California, Irvine
Irvine, CA 92697-4575
(949) 824-9921

This archive was generated by hypermail 2.1.6 : Wed Feb 29 2012 - 15:38:27 CST