Self-Consistent Molecular-Orbital Methods. VIII. Molecular Studies with Least Energy Minimal Atomic Orbitals

A minimal set of energy-optimized contracted Gaussian orbitals is used for single-determinant molecular-orbital studies of a set of small polyatomic molecules. Optimized scale factors for valence atomic orbitals are determined by energy variation and are found to be significantly greater than unity for hydrogen and carbon. The convergence of calculated properties with increasing size of Gaussian expansion is studied and found to be less rapid than in corresponding studies using a Slater-type minimal basis. Theoretical equilibrium geometries are determined. The agreement with experimental geometries is resonable but somewhat less satisfactory than with a Slater-type set.