[lammps-users] Is it possible to turn off 1-5 interaction for Stillinger-Weber type atoms?

Hello Lammps Users & Developers,

I am trying to simulate a molecule with hybrid atom types (SW and lj/cut). In my simulation, I wanted to turn off 1-5 interaction along with 1-4 interaction. I could turn off 1-4 interaction by special_bonds settings as lj 0.0 0.0 0.0 diheddral yes angle yes. However, it seems that I could not turn off 1-5 interactions with special bond_style, as the 1-5 interactions I wanted to turn off are between SW types. In the manual, it is written that it is not generally applicable for many body potentials. Thus, I was wondering whether there is any other way by which I could turn off this 1-5 interaction. Please note that I am using lammps 29Oct 2020 version and I have defined the bonds corresponding to the 1-5 pairs in bond sections of data file. Here I am writing the part of my input file where I am defining these stuff

special_bonds lj 0.0 0.0 0.0 angle yes dihedral yes

pair_style hybrid sw lj/cut 12.0
bond_style hybrid harmonic special

read_data gly.data

bond_coeff 2 harmonic 30 1.43 # C-O
bond_coeff 3 harmonic 30 1.43 # C-O
bond_coeff 1 harmonic 30 1.53 # C-C
bond_coeff 4 special 0.0 0.0

Also, I wanted to tune the 1-4 interactions between SW type atoms, which seem not to be working although it is clearly written in the manual that many body potentials are insensitive to special_bonds settings. Thus, I was wondering whether there is any other way for this. Any help would be appreciated.

Thanks in advance!


bond style special requires that pair styles between the pairs are pairwise additive, i.e. have a “single” method. The sw pair style does not fall into that category.
I do not want to go into details discussing the meaning of excluding manybody interactions for molecules, but what you are asking for is simply not possible in LAMMPS currently.

Thank you, Axel!