[gmx-users] Obtaining opls forcefield

[dgfd dgdfg]

oplsaa force field is situated in /usr/share/gromacs/top (on my PC) folder in gromacs format. If you want to generate oplsaa topology for non-protein molecule it is very comfortable to use acpype (git clone https://github.com/alanwilter/acpype.git) or Jorgensen server  http://zarbi.chem.yale.edu/ligpargen . For protein-like molecules pdb2gmx works. For small molecule oplsaa topology also can be written manually with your chemical intuition about atom types in common groups.