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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-weight:normal'>Dear gmx-users,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-weight:normal'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-weight:normal'>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.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-weight:normal'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-weight:normal'>Thank you very much in
advance,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-weight:normal'>Mikhail <o:p></o:p></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span lang=EN-GB style='font-family:"Arial","sans-serif";
font-weight:normal'>=============================================<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-family:"Arial","sans-serif";
font-weight:normal'>Dr Mikhail Stukan<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Arial","sans-serif";font-weight:
normal'>Schlumberger Dhahran Carbonate Research Center,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Arial","sans-serif";font-weight:
normal'>Dhahran Techno Valley - KFUPM,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Arial","sans-serif";font-weight:
normal'>P.O. Box 39011, Dammam / Doha Camp 31942,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Arial","sans-serif";font-weight:
normal'>Kingdom of Saudi Arabia</span><span style='font-family:"Arial","sans-serif";
font-weight:normal'><o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-family:"Arial","sans-serif";
font-weight:normal'>Tel: +966 3 331 0300 ext 6182<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-family:"Arial","sans-serif";
font-weight:normal'>Fax:+966 3 330 0845<br>
<a href="mailto:mstukan@slb.com"><span style='color:blue'>mstukan@slb.com</span></a><o:p></o:p></span></p>
<p class=MsoNormal><o:p> </o:p></p>
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