Structural and electronic properties of aluminum-based binary clusters

Abstract

We investigate the low-energy geometries and the electronic structure of several aluminum based clusters, viz. Al₄X₄, (X=Li, Na, K, Be, Mg, B, and Si) by first principle Born-Oppenheimer molecular dynamics within the framework of density-functional theory. We present a systematic analysis of the bonding properties and discuss the validity of spherical jellium model. We find that the structure of eigenstates for clusters with metallic elements conform to the spherical jellium model. The 20 valence electron systems Al₄Be₄ and Al₄Mg₄ exhibit a large highest-occupied-lowest-unoccupied (HOMO-LUMO) gap due to shell closing effect. In clusters containing alkali-metal atom, Al₄ behaves as a superatom that is ionically bonded to them. The Al-Al bond in both Al₄Si₄ and Al₄B₄ clusters is found to be covalent.