normal Water froze at 303 K in Gromacs 2016-rc1

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1 year 3 months ago #5776 by markussmiettinen
markussmiettinen created the topic: Water froze at 303 K in Gromacs 2016-rc1
I don't know if this is of great interest... but I thought it best to let at least the developers know, just in case it is.

While doing some testing with Gromacs 2016 rc1 , I managed to freeze Martini water boxes of 400 beads at 303.15 K; this happened with two independent initial configurations.

I used the Martini Straight parameters. The simulation files, including trajectories (freezing occurs at 400 ns in system 1, at 325 ns in system 2), are available for your viewing pleasure at Zenodo .

[In the end I ran an 8 times larger system (3200 beads) and it did not freeze anymore. This was enough for my purposes, so I did not dig deeper as to why the smaller boxes froze.]

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1 year 3 months ago - 1 year 3 months ago #5778 by peterkroon
peterkroon replied the topic: Water froze at 303 K in Gromacs 2016-rc1
Hi,

Martini water is essentially a Lennard-Jones fluid, and as such has a high tendency to freeze. For this reason we usually replace 10% of the water particles by so called anti-freeze particles. These are like the normal water particles, but larger, in order to break the packing.
Also, the polarizable water model should not show this behaviour.

Peter
Last Edit: 1 year 3 months ago by peterkroon.

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