[lammps-users] a question about special bonds

Dear sir,

I want to ask you a small question about lammps. The question is:
I have two kinds of dihedral interactions:
one is using charmm, the other is opls, the scaling factors for the
nonbonded interaction are different from each other. For charm, I use amber force field,
that means scale factor is 0.5 for LJ interaction, 5/6 for Coulombic interactions,
but for opls, the scale factor is 0.5 for both LJ interaction and Coulombic interactions.
I looked up the command “special_bonds”, but I still don’t know how to define that.

You can have a look at my input and data file. I defined the dihedral_style in the input file,
and give the dihedral Coeffs in the data file.

Do you have some suggestions about that?


c5mim.in (1.54 KB)

c5mim.data (606 KB)

I presume you are using the dihedral_style hybrid command.
The special_bond command really applies to pairwise
interactions. There isn't a way in LAMMPS to do something
different for a pairwise interaction depending on what dihedral
it is in. You would have to add some logic for that. Possibly
you could compute these interactions in the dihedral instead.