[gmx-users] Difference between semi isotropic coupling and surface tension option

[Ali Shomali]

Dear all Gromacs users

I'm simulating a monolayer at water/vacuum interface with Gromacs and I'm
studying surface tension and area per lipid variations. the problem that is
very confusing me on this subject is that when I use semiisotropic option
to impose a negative lateral pressure and so a specific surface tension ,
my final area per lipid is very different from surface tension option but
when I use my energy files, both of them (surface tension or semiisotropic
output) are resulted in a very same  surface tensions.so how is it possible
that the same surface tension gives different area per lipids? if the
procedures are different, which one is more accurate?
I appreciate your kind and helpful advises.