[gmx-users] water density

[Alexander Alexander]

Dear gromacs user,

I have a solid surface with TIP3P water on top of it in the vacuum part. I
am expecting to get the density of bulk TIP3P water (987 +/- 4.0 kg/m^3)
far from the surface in the middle of vacuum part, but, I always get
something around 895-905 kg/m^3 in spite of high equilibrating the system ,
more than 11 ns.
I can get the desired water density in a box with size as big as the vacuum
part including only water.
I know that I should increase the number of water, but "gmx solvate -maxsol
..." does not let me add water more than a specific number of maxsol into
vacuum part on top of the surface. I tried to deceive it by adding more
water in a bigger size box (in Z direction) and then reducing the size
after minimization, but then the SETTEL problem came up.

Any suggestion would be highly appreciated.

Best regards,
Alex