Potential curves for alkaline-earth dimers by density functional theory with long-range correlation corrections

Potential curves of alkaline-earth dimers, Be-2, Mg-2 and Ca-2, bound by London dispersion forces, are determined with the recently developed range separated hybrid method with perturbational long-range correlation corrections (RSH + MP2), and are compared to wave function approaches (MP2), to conventional density functional (LDA, PBE, BLYP. BPW91) and hybrid functional (PBE0, B3LYP) results. In contrast to rare gas dimers, functionals involving Becke's exchange are not repulsive, but yield a relatively profound potential well. The RSH + MP2 approach outperforms the MP2 method considerably and reduces the basis set superposition error. It represents a promising alternative for the study of larger alkaline-earth clusters. (c) 2005 Elsevier B.V. All rights reserved.