Reading force fields from default GROMACS FF folder doesn't work

[ricalessandri]

With atomistic force fields, usually one uses a line such as the following in the TOP file:

#include "gromos53a6.ff/forcefield.itp"

which tells GROMACS to look in /usr/local/gromacsXXXX/share/gromacs/top/ for the folder gromos53a6.ff containing forcefield.itp. But using such a TOP and running a command like:

polyply gen_coords -p system_P3HT_G56A3.top -o P3HT_n6_gromos.gro -name P3HT -box 8 8 8

leads to:

FileNotFoundError: [Errno 2] No such file or directory: 'gromos53a6.ff/forcefield.itp'

putting the absolute path then works. Which probably is totally fine; if so feel free to ignore this; maybe we can just make a note about this somewhere in the wiki/tutorial.

[pckroon]

Surprisingly non-straightforward: https://manual.gromacs.org/documentation/2021/user-guide/mdp-options.html?highlight=include#mdp-include https://manual.gromacs.org/documentation/2021/reference-manual/topologies/topology-file-formats.html?highlight=include I can't find which folders grompp searches, or in what order. On top of that, the include folders can be changed by the mdp file.

[fgrunewald]

Yes indeed, this is a conundrum I couldn't figure out so far. It becomes more problematic yet, when people have multiple gromacs installations, which do not all have the same FF parameters. Which one to choose? I think demanding a full path is the best course of action. But this should probably result in an Error message that is legible