I am trying to use the AMBER force field in LAMMPS. The dihedral term has a form similar to CHARMM. When I use dihedral_charmm I am also required to use pair_lj_charmm_coul_long, but I don't want a smoothed LJ function. I tried to write a new function but could not get it to work. Are there any other work arounds that I could use.