Bond properties of Be_3-7 clusters

Geometries, binding energies, and bonding properties have been investigated for the Be_3-7 clusters with ab initio molecular orbital theory using double (6-31G*) and triple [6-311(+)G*] ζ-basis sets with inclusion of the effects of electron correlation estimated with the Møller-Plesset perturbation (up to full MP4) and coupled cluster (QCI) theories. The geometries and binding energies suggest that the single-reference approach gives already reasonable results for Be₅. For the larger clusters Bader's electron density analyses reveals small concentrations of charge within groups of three Be atoms.