Maximum overlap population principle and direct calculation of bond order, valence and atomic charge

A maximum overlap population principle is introduced to give a very simple approximate scheme for calculating bond order, atomic valence and atomic charge directly from the eigenvectors of the AO overlap matrix without performing the ordinary molecular orbital calculation. The calculated results are close to or on the whole coincident with those obtained from the canonical molecular orbitals constructed by use of the ab initie calculation, which shows that the calculation scheme suggested in this paper is feasible.