[gmx-users] Calculating the interfacial tension between solid and liquid

[Lei]

Dear gmx users,
I am running a simulation to calculate the interfacial tension a virtual
lattice surface (name Z) and TIP4P water. I assembled a system where the
solid phase (Z) with thickness of 4nm enclosed by two water slabs(thicknees
of 4nm) in z direction. Then the system was put into an NVT ensemble. I
calculated the surface tension as (Pzz-0.5(Pxx+Pyy))*L/2, where L is the
length of the box in z direction.

However, the interfacial tension calculated following the above procedures
is very high. For example, the surface tension of TIP4P water is 59mN/m and
the calculated interfacial tension between solid and liquid is much larger
than that. Given the interfacial tension between solid and gas/vacuum is
negligible (I found this statement in some literature), the cosine of the
contact angle of water on such surface would be always be larger than 1,
which is not possible as the contact angle I observed is around 110
degrees.

Also some people use the method found in" Vázquez UO, Shinoda W, Moore PB,
Chiu CC, Nielsen SO. Calculating the surface tension between a flat solid
and a liquid: a theoretical and computer simulation study of three
topologically different methods. Journal of mathematical chemistry. 2009
Jan 1;45(1):161-74." In this method, they set interactions between solid
and vapor is purely repulsive, how can I manage that as the oplsaa force
field does not accept infinity number.

Thanks for your attention.