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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>You have a variable that is fluctuating over a range of 800+ units (three orders of magnitude) and want the average to be 1.0?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>It is not a problem as such. If you can get a large enough data set of pressure data, and it will have to be very large, then you might get it close to one.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>But as long the average you calculate is within may be an order of magnitude (-10 to 10) then there is nothing to get too worried about.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Catch ya,<br><br>Dr. Dallas Warren<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Medicinal Chemistry and Drug Action<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Monash Institute of Pharmaceutical Sciences</span><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>, Monash University<br>381 Royal Parade, Parkville VIC 3010<br>dallas.warren@monash.edu<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>+61 3 9903 9304<br>---------------------------------<br>When the only tool you own is a hammer, every problem begins to resemble a nail.</span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div style='border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt'><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> gmx-users-bounces@gromacs.org [mailto:gmx-users-bounces@gromacs.org] <b>On Behalf Of </b>Denny Frost<br><b>Sent:</b> Friday, 21 January 2011 9:07 AM<br><b>To:</b> gmx-users@gromacs.org<br><b>Subject:</b> [gmx-users] Inaccurate pressure readings<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I am running a variety of NPT simulations with polar, non-polar, and ionic compounds. Although my results for density agree well with experimental values, the pressures I get from g_energy are off by 1 to 3 orders of magnitude. In the log file, the pressure fluctuates around a lot from -400 to 400 bar, which seems to be normal according to other posts on this list, but the average (which is what g_energy gives me) is not 1.0 bar, as I specified. Does anyone know how to correct this problem?<o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Pressure coupling parameters:<o:p></o:p></p></div><div><div><p class=MsoNormal>Pcoupl = berendsen<o:p></o:p></p></div><div><p class=MsoNormal>pcoupltype = isotropic<o:p></o:p></p></div><div><p class=MsoNormal>tau_p = 1.0<o:p></o:p></p></div><div><p class=MsoNormal>ref_p = 1.0<o:p></o:p></p></div><div><p class=MsoNormal>compressibility = 4.5e-5<o:p></o:p></p></div></div></div></div></body></html>