Barostate and changing pressure along z only

User discussions
1

I have a system of (CH4-Water-CH4) and I’ve successfully run NVT, but I am struggling with NPT
I want the box size to change only along the z direction.
First of all, what does xy/yx, xz/zx and yz/zy components mean?
Should I use:
pcoupltype = anisotropic
tau_p = 5.0
ref_p = 1.0 1.0 1.0 0.0 0.0 0.0
compressibility = 0 0 4.5e-5 0 0 0

Also, the compressibilty value is for water (4.5e-5 bar^-1) but in my system I have methane and water. Should I change it?

Thanks!

2

Hi salem,

You can use semiisotropic instead:

pcoupltype = semiisotropic
tau_p = 5.0
ref_p = 0.0 1.0
compressibility = 0 0 4.5e-5

As far as I understand, compressibility only tunes the rate of relaxation to the correct pressure, so any value should work (but keeping the one of water seems a good idea).

Michele