VALENCE-BOND READING OF AB-INITIO MOLECULAR-ORBITAL CLUSTER MODEL WAVE-FUNCTIONS - THE NATURE OF CHEMICAL-BOND IN CORUNDUM

Two different methods of analysis of ab initio molecular orbital wavefunctions are proposed and applied to the study of the degree of ionicity of bulk corundum. Both methods are based on the philosophy of the valence bond approach. In the first method, the MO wavefunction is re-expressed in terms of orthogonal atomic orbitals Slater determinants. Limitations of this approach are widely discussed. In the second method a mixed approach is used which may be regarded as a fragment valence bond analysis. Both analyses indicate than the degree of ionicity of bulk corundum is larger than expected from chemical intuition.