Research On The Structural And Electronic Properties Of Ga_n,Ga_nN,In_n Clusters

During the past decade, the clusters of group-III have been intensively studied, because the s²p¹electron configuration makes their properties rather unique. In this paper, we have performed gradient-corrected density-functional calculations combined with genetic algorithm to investigate the structural and electronic properties of gallium, gallium nitride and indium clusters.To find the global minimum structures, we first employed an unbiased genetic algorithm (GA) to generate a large number of structural isomers on the potential-energy surface. Then we further optimized the initial configurations using the first principles approach. Based on the lowest-energy structures obtained we discussed the size-dependent physical properties of Ga_n, Ga_nN, Inn(n≤13) clusters such as binding energy, HOMO-LUMO gaps, second-order difference of total energies, vertical ionization potentials (IPs) and adiabatic electron affinities (EAs). The ground state structures of Inn clusters were in most case very similar to that of the Ga_n clusters. With the increase of cluster size, both kinds of clusters tend to adopt atom-centered compact structures. Our theoretical ionization potentials and electron affinities of gallium and indium clusters agree excellently with experimental results, which approve the accuracy of our present computational scheme.Gallium nitride is an important semiconducting material, and has drawn great attention in recent years. There are numerous theoretical and experimental studies on structural, electronic and optical properties of both surface and bulk phases of GaN. However, less attention has been given to the research of GaN clusters. In this work, we studied the structural and electronic properties of Ga_nN (n=2-12) clusters. Through Mulliken population analysis, we found charge transfers from the Ga the N site and the ionic bonding changes into covalent bonding as cluster size increases. The ground state structures of small Ga_nN (n≤10) clusters were found to be N-centered configurations. When n≥11, Ga_nN clusters exhibit similar lowest-energy structure and binding energy of Ga_m (m=n+1) clusters. Ga₈, In₈ and Ga₃N exhibit particularly higher stability and are identified as magic-number clusters.