Convergence of multibody expansions for alkaline earth metals. Contrast between magnesium and beryllium clusters

Publisher Website
Google Scholar
Abstract
An ab anitio SCF–LCAO–MO study of nonadditive three‐ and four‐body interaction energies in Mg3 (equilateral and linear) and Mg4 (tetrahedral) clusters is presented. The relative importance of these few‐body terms to the interaction energy is at most 39% for three‐ and 8% for four‐body terms. This lies in marked contrast with the case of Be clusters where these terms can have a relative weight of up to 76%, and 31.6%, respectively. The reason for such radically different nonadditive effects is discussed. Some new results for Be3, Be4, and Be5 clusters are presented confirming this is a case where multibody expansions are expected to be very slowly convergent. Finally these results provide an explanation for the poor convergence of the chemisorption energy of an H atom as a function of the size of Ben clusters.