[gmx-users] gromos force field

p buscemi pbuscemi at q.com
Sat Sep 21 18:44:51 CEST 2019

Dear Users,
I often use Gromos force field because ATB provides top files for reasonably large molecules - 1000 atoms. With Gromacs 2019.3 the error now appears:
The GROMOS force fields have been parametrized with a physically
incorrect multiple-time-stepping scheme for a twin-range cut-off. When
used with a single-range cut-off (or a correct Trotter
multiple-time-stepping scheme), physical properties, such as the density,
might differ from the intended values. Check if molecules in your system
are affected by such issues before proceeding. Further information may be
available at https://redmine.gromacs.org/issues/2884.

while message is clear enough, just how large an error in density is anticipated ? A 10 % error in polymer solution may be tolerable. A 2 % error in a crystal or binding site may be a concern.
Gromacs indicated that Gromos may be dropped for v 2020. Is there no other option - llike fixing the time-stepping-scheme. Or must I not use the twin-cutoff typically presented in the mpd files ?
There is a conversion from Gromos top to Amber, but would not the error be translated as well ?
Any comments on a resolution would be appreciated.

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