Non-empirical molecular orbital calculations based on Slater-type orbitals. A restricted use of Gaussian expansions

Abstract

An ab-initio SCFMO technique of balanced computational speed and precision is described for use with Slater-type orbitals as basis. All of the more significant integrals over STO'S are evaluated with full arithmetic accuracy but the ?non-NDDO? two-electron integrals are evaluated less precisely by using small Gaussian expansions.     The overall numerical accuracy achieved in calculations of total energy and <r> are illustrated for a number of small molecules using both 2G and 3G expansions. The performance, especially with respect to energy calculations, is clearly superior to that of analogous methods that have recently been described.