Geometrical structure, electronic states and stability of NinAl+ clusters

Various structural possibilities for binary alloy NinAl+ (n = 1-8) cationic isomers have been investigated using density functional method (BPW91) with the effective core potential LanL2DZ basis set. Our calculations predicted the existence of a number of previously unknown isomers. The charged-induced structural changes in these cations have been discussed. With Nin+1 forming base, replacing a Ni atom at marginal positions by an Al atom would be helpful to find the stable structures of NinAl+ cationic clusters and neutral NinAl clusters quickly and correctly. The resulting geometries show that the aluminum atom remains on the surface of the clusters. Moreover, the obtained clusters prefer to adopt three-dimensional (3D) structures at the smaller number of nickel atoms compared with the pure Nin+1 clusters (n ⩾ 3), the tetragonal and pentagonal configurations are favored energetically when n > 5. The most stable structures of NinAl+ clusters are same as the neutral ones except n = 7. The analysis of stabilization energies reveals that Ni5Al and Ni4Al+ clusters are the relatively most stable in this series.