Bridging the gap over size scales: A Green's-function method to combine tight-binding and semiempirical force calculations

A method to calculate local electronic structure and interatomic forces for molecular dynamics simulation of a materials system with two size scales, is described. In the method, the interactions for the larger scale subsyste m are modeled with semiempirical potentials, and the interactions for the s maller scale subsystem are calculated quantum mechanically. Interatomic Hel lman-Feynman forces can be calculated using the off-diagonal matrix element s of density matrix derived from Green's function and the gradients of the matrix elements of the tight-binding Hamiltonian matrix. The elements of Gr een's function for semiempirical particles are modeled in some simple prede fined form, while Green's function for the rest of the particles is calcula ted in tight-binding basis using Dyson's equation. As an example, dissociat ive adsorption of O-2 On a stepped Pd(110) surface is simulated. [S0163-182 9(99)02228-6].