Analytic bond-order potentials beyond Tersoff-Brenner. II. Application to the hydrocarbons

Abstract

The accuracy of the analytic bond-order potentials (BOP's) that were derived in the previous paper within the tight-binding (TB) formalism is studied for the case of diamond, graphite, and the hydrocarbon molecules. The simplified four-level variant, BOP4S, is found to reproduce the TB bond orders of the C-H and C-C $\ensuremath{\sigma}$ bonds to better than $6%$ due partly to the inclusion of the shape parameter ${(b}_{2}{/b}_{1}{)}^{2}.$ The two-level matrix-derived expression BOP2M is shown to provide a good description of the saturated and conjugate $\ensuremath{\pi}$ bonds, thereby overcoming the deficiencies of the Tersoff potential that are associated with overbinding of radicals and poor treatment of conjugacy. The analytic BOP's reproduce the C-H and C-C bond energies to better than $0.9$ eV per bond. The errors would be reduced if the analytic potentials were fitted to experiment rather than predicted directly from known TB parameters.