Density functional calculation of structural and electronic properties of Tin-xAlx (n =2-8, 13, x=0-n) clusters

Using density-functional theory, a systematic theoretical study on the structural and electronic properties of Tin-xAlx (n = 2-8, 13, x = 0-n) clusters has been performed. Tin-xAlx (n = 2-8, x = 1-n-1) clusters often employ the substitution patterns based on the structures of pure Tin cluster, while all Ti13-xAlx (x = 0-13) clusters adopt the icosahedral motif. The preference of Ti (Al) atom for high coordination number site experiences a transition with size increasing. In the range of n = 5, 6, the preference for high CN site is Ti atom, while for medium size, e.g., n = 13, Al atom. The clusters with around 7-8 atoms might represent a region of transition. The transition originates from the valent transition of Al atom from one to three. Ti2Al2, TiAl4, Ti4Al2, Ti4Al3, and Ti4Al4 clusters are the most stable ones for a given size when comparing with all possible compositions. TiAl4 cluster possesses the extraordinary stability originating from aromaticity.