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?
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. 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. Catch ya, Dr. Dallas Warren Medicinal Chemistry and Drug Action Monash Institute of Pharmaceutical Sciences, Monash University 381 Royal Parade, Parkville VIC 3010 dallas.war...@monash.edu +61 3 9903 9304 --------------------------------- When the only tool you own is a hammer, every problem begins to resemble a nail. From: gmx-users-boun...@gromacs.org [mailto:gmx-users-boun...@gromacs.org] On Behalf Of Denny Frost Sent: Friday, 21 January 2011 9:07 AM To: gmx-users@gromacs.org Subject: [gmx-users] Inaccurate pressure readings 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? Pressure coupling parameters: Pcoupl = berendsen pcoupltype = isotropic tau_p = 1.0 ref_p = 1.0 compressibility = 4.5e-5
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