Multi-Atom Bonding in Aluminium over a Wide Range of Coordination Number

Ab initio calculations are presented of the cohesive energies of aluminium in a number of diverse hypothetical structures which span a wide range of the coordination number, C, from C = 0 to C = 12. The calculations have been performed to investigate the nature of multi-atom bonding, its dependence on C and to form a database for testing and developing empirical and semi-empirical models. The results support the saturation of cohesive energy for large C predicted by several simple theoretical models. Calculations on the same structures using semi-empirical schemes suggest that these methods might have a greater degree of accuracy than had previously been believed.