Extracting polarized atomic orbitals from molecular orbital calculations

Abstract

We present a class of methods for extracting a polarized atomic orbital (EPAO) minimal basis set from a converged molecular orbital (MO) calculation. Unlike minimal basis sets obtained from previous approaches, EPAOs rigorously contain the occupied molecular orbital space. EPAOs achieve this exactness because their spatial extent is not restricted. Nonetheless, EPAOs are optimally localized with respect to a localization criterion and are essentially single-centered. EPAOs provide an alternative scheme for partitioning the electron density into atomic subspaces. Therefore, they can be used to determine atomic and chemical group properties such as charge populations. Since EPAOs provide a compact description to the occupied space, they may have other computational applications such as in local correlation methods. Additionally, the EPAOs give a description of valence antibonding orbitals that may be appropriate for nondynamical electron correlation. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 76: 169–184, 2000