Population analysis based on occupation numbers of modified atomic orbitals (MAOs)

A new interpretational scheme is proposed for the analysis of molecular wavefunctions. Starting from the molecular density operator we first construct a minimal set of MAOs from the requirement that the MOs can be represented as closely as possible by the MAOs. We then use the MAOs to compute atomic occupation numbers N and shared electron numbers σ. The molecular density is then discussed in terms of N and σ. This approach has the following advantages: 1) it is generally applicable, 2) the quantities N and σ are virtually basis set independent, 3) the quantities N and σ fulfil the intuitively expected boundary conditions, 4) the simultaneous consideration of N and σ allows for a more reliable description of chemical bonding than consideration of atomic charges only.