I am using CLASS 2 force field for the simulation of PDMS Coarse-Grained beads. While I have the data for PDMS beads from a certain paper, my system also consits of some molecules (specifically Fe (III) - 2,6 Pyridine-dicarboxamide complexes) for which I could not find Class 2 Parameters in literature. As such, I plan to derive them. However, I do not know how to proceed.

The literature I've looked at have passingly mentioned that they used quantum mechanical calculations and applied to all-atom simulation from where the Coarse-grained model was obtained. But, none of them go into detail about the methodology.

I have experience with DFT using the VASP package, but it was limited to electronic structure calculations. I do not know how to use DFT to gain insight on bond, angle, dihedral and improper interactions for all-atom simulations. Any help on this matter would be useful.