[gmx-users] Question about phospholipid monolayer on a water/air interface

[Sergio Garay]

Hi

My name is Sergio Garay, and I'm working on a simulation of a 
phospholipid monolayer on a water/air interface. To mimic that system I 
have constructed a rectangular box with a thick layer of water at the 
center, two monolayer of lipids (with their polar heads pointing toward 
water) at each side, an finally two thick vacuum layer a each side (I 
think, the air component could not be considered here due to the size of 
the simulation system)
I would like to make a constant Area calculation, to obtain the surface 
tension of the system. My questions is:

What is the more adecuate condition to do this?

Although the normal pressure would be 1 atm at the experimental 
condition, this pressure is not compatible with the vacuum in the 
simulation box unless the compressibility in the Z direction would be 
fixed at value 0.0 to keep the Z box dimension fixed.

1) Is it convenient to simulate at fixed volume (NVT)

or
2) at the constant Area (x,y) ensemble with normal pressure 0 / 1 atm, 
normal compressibility equal 0.0, and x,y compressibilities equal 0 ? A 
kind of NPzAT ensemble

Is there a more appropiate alternative?


Thank you in advance