Selected valence electron split‐shell MO calculations on Cu₂, Ag₂, and Au₂

Abstract

The Harris-Pohl selected valence electron split-shell MO model [ 11 has proved quite successful in the calculation of ground-state properties of a number of o-bonded diatomics [2-41. The purpose of this investigation is to extend this model to the dimers of Cu, Ag, and Au by regarding them as isovalent with the alkali dimers. Since the results of split-shell MO calculations on the latter molecules were obtained in excellent agreement with experiment, it is anticipated that a similar model might prove successful for the dimers of Cu, Ag, and Au as well. Recently, the binding energy and equilibrium bondlengths of these molecules have been calculated [5] by the Heitler-London VB method using nodeless s-type orbitals obtained from an atomic hard-core model. An extended Hiickel calculation on Cuz [6] and an ab initio calculation each on Cuz [7] and Au2 [8] have also been reported.The method of calculation as used in the case of alkali dimers [2], when followed in its entirety, does not give satisfactory results for the present systems. Based on empirical considerations, we have, therefore, introduced the following modifications in the method. The valence-state electron affinity of Ag and Au being not available, the one-center electron repulsion integral could not be calculated in the usual way. We have approximated this integral as follows: