PolyParGen provides OPLS-AA and Amber force field parameters for polymers or large molecules.
In the case that PolyParGen generates OPLS-AA parameters, PolyParGen leverages LigParGen [2] and BOSS [3].
On the other hand, PolyParGen leverages Antechamber [4] and ACPYPE [5] to make Amber parameters.
If users want to use the atomic charge of ab initio calculation, user just select the option of ab initio calculation. Ab initio software is NWChem [6].
Also, the supports input file is CML format at current version. The previous version (v1) supports PDB, MOL, MOL2 and CML.
The support of PolyParGen version 1 has been suspended to create accurate potential parameters.
If you want to make the OPLS-AA force field parameters for organic molecules and ligands which have within 200 atoms, you should use LigParGen service.