After through study of manual and many research paper I prepared my simulation file to calculate the interfacial properties of oil-water system in presence of a surfactant and alocohals.
The following confusion arises when I see literature and manual for pressure coupling option.
The algorithm in manual says:
" When a periodic system consists of more than one phase, separated by surfaces which are parallel to the xy-plane, the surface tension and the z-component of the pressure can be coupled to a pressure bath. Presently, this only works with the Berendsen pressure coupling algorithm in GROMACS. The average surface tension γ(t) can be calculated from the difference between the normal and the lateral pressure"
This means that pcoupl should be Brendsen and
pcoupltypeshould be surface tension? Right?
However, What I found that many researchers have used
Parrinello-Rahmanfor instead of Brendsen and reported results in paper. This shouldn’t be right as per manual. I did it for my system using both and grompp didn’t complained any time. The results were pretty close though.
Not only that, i found people have not used surface tension coupling and used semi-isotropic and still were able to compute surface tension.
I searched old forums too. Nobody had a clear answers there. Few people had suggested that it might have been implemented but may not have been updated in manuals.
- Another point I would ask is about ref p and value
As manual says for surface tension coupling :
Two ref p value are needed
"The first -ref-p value is the reference surface tension times the number of surfaces
bar nm, the second value is the reference z-pressure
many time a constant pressure of 1 bar and zero compressibility is used in xy plane ( first ref-p value).
what reference surface tension should we be using here?