[lammps-users] beta-Sn crystal structure and MEAM

I'm having some trouble creating the "lattice user" line for an MEAM simulation of Sn in its beta-Sn crystal structure. I'm also not sure how to incorporate both lattice parameters "a" and "c" into the in-file lattice command.

The following gives me an ERROR: Illegal lattice command:

The basis values have to be between 0 and 1. So I think
you want something like:

basis 0.0 0.75 0.125

Also, with this primitive vector: A3 = ½ a X + ½ a Y + ½ c Z
and assuming c != a, then I think you would want the LAMMPS a3 to be
something like:

a3 0.5 0.5 0.5*c/a

Regardless, you will want to viz the created lattice of atoms to be
sure LAMMPS did what you expect, especially w/ respect to periodic