Empirical two-body potential for solid silicon nitride, boron nitride, and borosilazane modifications

A short-ranged classical force-field for the modeling of silicon nitrides, boron nitrides, and borosilazanes (Si/B/N) has been derived on the basis of experimental and ab initio solid state and diatomic molecular data. The potential is a sum of pure two-body interaction terms with functional forms apt for fraction simulation. Structural parameters of hypothetical Si₃B₃N₇ polymorphs and crystalline boron and silicon nitrides containing threefold or fourfold coordinated boron and nitrogen and fourfold or sixfold coordinated silicon are well reproduced. The quality of second-order properties such as vibrational frequencies, bulk moduli, and elastic constants is more sensitive to the atomic coordination. Very good agreement with experiment is observed for BN and Si₃N₄ modifications with trigonal nitrogen coordination.