[gmx-users] Gromos DPPC bilayer: different results for 4.0.7 and 4.6.5

[Lutz Maibaum]

On Dec 17, 2013, at 1:55 PM, Mark Abraham <mark.j.abraham at gmail.com> wrote:
> I would suggest using mdrun -rerun magic-configuration.gro -s some.tpr on
> whatever combinations of .mdp settings and GROMACS versions make sense, to
> observe that there is a difference that can be reproduced, and which .edr
> fields show it.

I did that for the 53A6-L forcefield and the configuration posted at

http://faculty.washington.edu/maibaum/dppc_comparison/sample.gro

The various "energies" reported by Gromacs 4.0.7 and 4.6.5 are those:

http://faculty.washington.edu/maibaum/dppc_comparison/g_energy_comparison.pdf

It does look like the main differences come from the virial (and therefore pressure). I was surprised that even the temperatures are slightly different. These calculations are done in single precision.

> correction terms before recording any data. Note that the RF terms need not
> be the primary problem - using the wrong form of long-range correction
> would be a possible candidate, and there's doubtless others.

Dispersion correction has been turned off, so hopefully that's not the culprit (but of course you are right that there are plenty others).

Best,

  Lutz