[gmx-users] isothermal compressibility

Shyno Mathew sm3334 at columbia.edu
Tue Apr 3 23:08:05 CEST 2012

Hello everyone,

I am new to gromacs and is trying to set up a protein simulation with
anisotropic pressure coupling using Berendsen barostat. For isothermal
compressibility, the user manual suggested the value as 4.6 x 10^-5 1/bar
as it is the isothermal compressibility for water at 1 atm, 300K. So this
means regardless of the system I need to consider only the isothermal
compressibility of the solvent surrounding it, correct?
I am not sure if I should use the same values for all xx, yy, zz, xy/yx,
xz/zx and yz/zy components for both pressure and isothermal compressibility?
or should I set the off diagonal values to zero like below:
compressibility          = 4.6e-5  4.6e-5  4.6e-5  0 0 0
ref_p                    = 1.0 1.0  1.0  0.0 0.0  0.0

Can some one explain the logic behind this?

thanks in advance,

Shyno Mathew
PhD student
Department of Chemical Engineering
Columbia University
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