[gmx-users] Re: Water density

Wei Fu fuwei at adrik.bchs.uh.edu
Wed May 12 14:22:19 CEST 2004

Hi, Erik and David, Thanks so much for your reply. I just use the
experimetal water density value (0.829g/l) at my desired temperature

When I turn on the pressure scalling, the system is equlibrated, while the
box volume decreases, i.e., the water density increases. 

I want to try different pressure, then get the desired water density. I am
not sure if it is feasible, just try.



First, when the box volume decreases the density will increase and vice 
versa - there's a strict inverse proportionality between them :-)

 From your description it sounds as if you turned on pressure scaling 
for a system that wasn't equilibrated. In that case, the temporary high 
forces this might lead to a rapid volume expansion.

If you try to simulate water in a box that is too large you'll get 
clusters. Compare with a glass of water in a space shuttle - the water 
won't expand to fill the entire shuttle at low density, but will form a 
sphere in vacuum.



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