Structure and stability of Al-doped small Na clusters: Na_nAl (n=1,10)

Abstract

We have investigated the ground-state geometries of aluminum-doped sodium clusters Na_nAl (n=1,10) using an ab initio molecular-dynamics method. It is seen that a single Al impurity atom affects significantly the geometries of small Na_n (n<~6) clusters, whereas the effect is less pronounced for large clusters. Our results show an early appearance of nonplanar ground-state geometries and it is observed that for n>~6 the Al atom gets trapped inside the Na cage. The stability of these clusters has been examined from the systematic analysis of energetics. This indicates Na₅Al and Na₇Al having 8 and 10 valence electrons to be the stable clusters.