[gmx-users] Problem with pressure form g_energy
mstukan at slb.com
Sat Sep 18 13:57:32 CEST 2010
I have experienced the following problem with g_energy program. The problem is the same for at least three versions (3.3.4, 4.0.7 and 4.5.1). When I calculate pressure value (in NPT simulation) using g_energy I obtain the result (average value plus errors, drift etc.) and the instantaneous values of the pressure in energy.xvg file. But then, if I try to calculate the average value based on these instantaneous values I have significantly different number. I assume that the problem could be in precision (I run double precision version of GROMACS). Option -dp in g_energy changes nothing, probably rounding is at some higher level than that. Is there any way to solve this issue? Should I also trust the result of g_energy rather than data in energy.xvg? For the parameters that expose minor fluctuations (volume, density, temperature) this problem doesn't occur.
Thank you very much in advance,
Dr Mikhail Stukan
Schlumberger Dhahran Carbonate Research Center,
Dhahran Techno Valley - KFUPM,
P.O. Box 39011, Dammam / Doha Camp 31942,
Kingdom of Saudi Arabia
Tel: +966 3 331 0300 ext 6182
Fax:+966 3 330 0845
mstukan at slb.com<mailto:mstukan at slb.com>
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