Special bonds for CHARMM forcefield

I’m simulating a flexible graphene in lammps using CHARMM27 forcefield parameters. Based on CHARMM27 forcfield parameters, no 1-4 exclusion policy is imposed on the carbon atoms of the graphene. So I prefer to set the weighting factor of the charmm dihedral style to zero and instead use special_bonds command and set 1-4 scaling factor to 1. To model the LJ interaction between carbon atoms I’m using pair_style lj/charmm/coul/charmm command (since I prefer to have the switching function). However, as I explained, do not need any 1-4 exclusion, so my question is that if I use special_bonds lj/coul 0 0 1, does it function on pair style of lj/charmm or it only functions on pair_style lj/cut ?


I’m not clear what you are asking. The special_bonds command

applies to whatever pair style you are using, lj/charmm or lj/cut.

If you are using a pair hybrid with multiple sub-styles, you can

adjust the weighting factors of inidividual sub-styles via

the pair_modify “pair” option.