Assistance with Generating .top File for Non-Protein Residues

GROMACS version: 2024.2
GROMACS modification: Yes/No
I want to generate a .top file for non-protein residues? I have a PDB file for polyvinyl alcohol and LiBr, and I intend to use the OPLS-AA force field. I attempted to create it using the LigParGen server, but I encountered an error. Could you please assist me with this?