Population Analysis of Pair Densities - A Study of Bassis Set Dependence

Based on work reported by several authors, one of us (RP) has introduced a Mulliken-like population analysis of pair densities. This scheme, introduced first at the semi-empirical level, was subsequently generalised both for SCF and for post-SCF ab initio methods. A potential problem is the basis set dependence that can be expected for all kinds ofMulliken-like approaches. The main purpose of the present study is to quantify this basis set dependence for a range of simple molecules, using basis sets ranging from STO-3Gto TZVPquality. It is shown, except for low quality basis sets, that the »effective«pair populations derived from ab initio SCF calculations are relatively insensitive to the choice of basis set.