[gmx-users] compressing a box of water droplets into a homogeneous solution of liquid water

chris.neale at utoronto.ca chris.neale at utoronto.ca
Mon Mar 21 16:53:02 CET 2011

Dear users:

I recently came across a system that was composed of tip4p water vapor  
droplets separated by vacuum. This system is what you might get if you  
did a NVT simulation of water with a box that was 10 times too large  
for the number of water molecules.

I was surprised to see that this system did not collapse to any  
significant extent during 200 ps of NPT equilibration at 1 atm using  
the Berendsen thermostat with tau_p=1.0 and the sd integrator and a  
colombic cut-off. (We also tried a number of other integrator/pressure  
coupling combinations with the same results).

I had assumed that such collapse would occur quite rapidly. This does  
not seem to be the case (no noticeable contraction within 200 ps).

Has anybody else done anything like this? Can anybody comment on their  
expectations/experience of collapse from the gas state to the liquid  
state under standard NPT conditions?

Thank you,

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