charmm parameter for graphene oxide

,I want to simulate graphene oxide with charmm force field. hydroxyl
and epoxy group was attached to graphene randomly distributed in the
sheet. and Graphene edges is sp2 . I have not force field parameter
for epoxy or hydroxyl or ... for my GO. and i do not now that which
atom type from charmm parameter is correct for this GO.
I saw that you used charmm parameter for GO in this

this is a question that you should post in the charmm forums to get
answers from the charmm experts. this has next to nothing to do with
LAMMPS. it is a force field question.