I am trying to do an NPT simulation. I have a solid surface substrate and a fluid. The manual says that the pressure is calculated based on all the atoms in the system. Is there any way to only use the atoms in the fluid when calculating the pressure.
Otherwise, it is very difficult for me to get my system at the required densities - If I do a simulation on the fluid only, I get my required densities at the correct pressure/temperature. But when I add my solid substrate, this no longer works as the atoms from the surface substrate are also used, which has large effects on the pressure of my system.
Thank You,
Michael Doig.