In harmonic dihedral style I see just one term including n, d and K, but in the dihedral that I want to define in my system, there is a summation of harmonic dihedral styles. I am going to know, is it possible to define this summation as I said in the previous?
there is no summation with a hybrid dihedral style,
each line defining a type will override the previous one.
this is how it is documented, what i already stated, and
how it works. it would help you a lot, if you would
pay more attention.
you either have to program a custom dihedral style
yourself or tabulate your unsupported style.
If you tablulate it you can use the dihedral_style table
command. If the formula you want is not
already one of the LAMMPS dihedral potentials,
that is your only option, other than programming
it yourself as a new dihedral style.