[gmx-users] Inaccurate pressure readings

[Warren Gallin]

This seems odd.

If a value fluctuates between -400 and +400, how can the average be outside the range?

Warren Gallin

On 2011-01-20, at 3:24 PM, Denny Frost wrote:

> from -1000 to 1000, depending on the system.  The simulation box is 8x8x8 nm (roughly) and contains about 12,000 atoms
> 
> On Thu, Jan 20, 2011 at 3:09 PM, Justin A. Lemkul <jalemkul at vt.edu> wrote:
> 
> 
> Denny Frost wrote:
> 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?
> 
> 
> What is the average value you're getting?  How long are your simulations?
> 
> -Justin
> 
> 
> Pressure coupling parameters:
> Pcoupl              =  berendsen
> pcoupltype          =  isotropic
> tau_p                   =  1.0
> ref_p                   =  1.0
> compressibility     =  4.5e-5
> 
> 
> -- 
> ========================================
> 
> Justin A. Lemkul
> Ph.D. Candidate
> ICTAS Doctoral Scholar
> MILES-IGERT Trainee
> Department of Biochemistry
> Virginia Tech
> Blacksburg, VA
> jalemkul[at]vt.edu | (540) 231-9080
> http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin
> 
> ========================================
> -- 
> gmx-users mailing list    gmx-users at gromacs.org
> http://lists.gromacs.org/mailman/listinfo/gmx-users
> Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/Search before posting!
> Please don't post (un)subscribe requests to the list. Use the www interface or send it to gmx-users-request at gromacs.org.
> Can't post? Read http://www.gromacs.org/Support/Mailing_Lists
> 
> -- 
> gmx-users mailing list    gmx-users at gromacs.org
> http://lists.gromacs.org/mailman/listinfo/gmx-users
> Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/Search before posting!
> Please don't post (un)subscribe requests to the list. Use the 
> www interface or send it to gmx-users-request at gromacs.org.
> Can't post? Read http://www.gromacs.org/Support/Mailing_Lists