xnn.ffnn.models.ffield.lammps_pair_parameters#

xnn.ffnn.models.ffield.lammps_pair_parameters(p, spec, offd)[source]#

Fill the pair radii and van der Waals parameters as LAMMPS does, in place.

pair_style reaxff derives every pair from the atomic values – the arithmetic mean of the sigma / pi / double-pi bond radii and the geometric mean of Devdw, rvdw and alfa – and then lets an off-diagonal entry override each value that is positive. Negative atomic pi radii are kept: whether a pi channel exists is decided per atom (see ReaxFF), not from the pair radius. Every pair of spec gets an entry in both orientations.

Parameters:

p (dict) – Flat parameter dictionary, modified in place.
spec (list[str]) – Species symbols.
offd (list[str]) – Off-diagonal types listed in the library.

Return type:

None