A novel ab initio approach to problems of electronic structure calculations of the gas‐solid interface

A calculational procedure that permits the approximation of an infinite or semi‐infinite lattice by a finite cluster is described and applied to the surfaces of the allotropes of carbon—diamond and graphite. The Hartree‐Fock‐Roothaan equations are modified to permit a portion of the wave‐function to be fixed while other parts are variationally determined in the field generated by themselves and by the fixed part. A projection technique is developed to transfer a representation of the electronic structure of the variational part to the fixed part, and self‐defining cycles are followed to convergence. Recent results for diamond and graphite surfaces suggest that for a given finite size of cluster, the procedures result in a more uniform description of electron densities than does a straightforward SCF calculation.