ASYMPTOTIC BOUNDARY-CONDITIONS IN CLUSTER SIMULATION OF ELECTRONIC-STRUCTURES FOR INFINITE AND SEMIINFINITE CRYSTALS .1. INFINITE CRYSTALS

A new method is proposed for determining the local electronic structur e of an infinite or a semi-infinite crystal using asymptotically accur ate boundary conditions imposed on the matrix elements of Green's func tions in the lattice point representation for the boundary atoms of th e cluster. The boundary conditions are determined in a self-consistent manner from cluster calculations. Introduction of these conditions is equivalent to the calculation of the out-of-cluster region of the cry stal; this gives a continuous spectrum of electronic stares, which is in good agreement with the crystal spectrum.