I plan to use the Vashishta potential for silicon nitride by manually inputting the relevant parameters to the already existing Vashishta potentials (for example SiC).
I noticed that there are zero entries whenever the neighbor atoms are different. Why is that?
In the LAMMPS manual, it says, "Two-body parameters appearing in entries where the 2nd and 3rd elements are different are stored but never used. It is good practice to enter zero for these values." This explains why there are zero entries for the two-body potential terms, but what about three-body terms? why are they zero?