[gmx-users] Pressure Calculation

[Farshid Mostowfi]

Hi david;

Thanks for your reply. I considered the that factor (16.6) but it didn't work.
Here is the sample calculations, (g_energy output results are at the bottom 
of the page):
2/V(Ekin-Vir(1,1))*16.6  =   2/343(84749.94-211153.88)*16.6   =  6155bar

I'd appreciate it if you let me know where my mistake is.
Thanks,
Farshid


g_energy output results:

Ekin=84749.94 (Kj/mol)
V=343 (nm3)
P= 1114.501 (bar)


        	21153.88 	1892.37  	-5107.3
Vir=  	1820.15  	18818.25 	-4488.1
        	-5025.92   	-4484.56  	10246.22


     719.3521	195.9087	515.1461
P= 188.9157	920.3499	450.6406
      507.2669	450.298	         	1703.802


On Saturday 10 July 2004 14:16, you wrote:
> On Sat, 2004-07-10 at 20:44, Farshid Mostowfi wrote:
> > Hello Everyone;
> >
> > I have a problem with pressure calculations. Based on the manual (pp 21,
> > eq 3.16) the pressure tensor is calculated using the difference between
> > kinetic energy and virial tensor : P=2/V*(Ekin-Vir)
> > I extracted the kinetic energy, virial and pressure tensors using
> > g_energy from energy file, but they don't match and I don't know why.
> > Is there anybody who can help me with this problem?
>
> check units. there is a magic factor 16.6 somewhere.
>
> > Thanks in advance.
> >
> > Regards,
> > Farshid
> > Ph.D student
> > Mechanical Engineering Dept.
> > University of Alberta
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