Electron Localizability Indicators ELI-D and ELIA for Highly Correlated Wavefunctions of Homonuclear Dimers. I. Li2, Be2, B2, and C2

Electron localizability indicators based on the parallel-spin electron pair density (ELI-D) and the antiparallel-spin electron pair density (ELIA) are studied for the correlated ground-state wavefunctions of Li-2, Be-2, B-2, and C-2 diatomic molecules. Different basis sets and reference spaces are used for the multireference configuration interaction method following the complete active space calculations to investigate the local effect of electron correlation on the extent of electron localizability in position space determined by the two functionals. The results are complemented by calculations of effective bond order, vibrational frequency, and Laplacian of the electron density at the bond midpoint. It turns out that for Li-2, B-2, and C-2 the reliable topology of ELI-D is obtained only at the correlated level of theory. (C) 2009 Wiley Periodicals, Inc. Comput Chem 31: 1504-1519,2010