The structure and energetic of AlAs n ( n = 1–15) clusters: A first-principles study

Abstract

Geometric structures of AlAs n ( n = 1–15) clusters are reported. The binding energy, dissociation energy, stability of these clusters are studied with the three-parameter hybrid generalized gradient approximation (GGA) due to Becke–Lee–Yang–Parr (B3LYP). Ionization potentials, electron affinities, hardness, and static polarizabilities are calculated for the ground-state structures within the same method. The growth pattern for AlAs n ( n = 6–15) clusters is Al-substituted pure As n+1 clusters and it keeps the similar frameworks of the most stable As n+1 clusters (for example AlAs 6, AlAs 7, AlAs 9, AlAs 14 and AlAs 15 clusters) or capping the different sides of the low-lying geometry of As n clusters (for example AlAs 8, AlAs 10, AlAs 11, and AlAs 12 clusters). The Al atom prefer to occupy a peripheral position for n < 12, and starting from n = 12 clusters, the Al atom completely falls into the center of the As frame. The above growth pattern is not suitable for AlAs n ( n = 1–5, 13) clusters. The odd–even oscillations from AlAs n ( n = 5–15) in the dissociation energy, the second-order energy differences, the HOMO–LUMO gaps, the electron affinity, and the hardness are more pronounced. The stability analysis based on the energies clearly shows the AlAs n clusters from n = 5 with an even number of valence electrons are more stable than clusters with odd number of valence electrons.