We have investigated the ground-state geometries of aluminum-doped sod
ium clusters NanAl (n=1,10) using an ab initio molecular-dynamics meth
od. It is seen that a single Al impurity atom affects significantly th
e geometries of small Na-n (n less than or equal to 6) clusters, where
as the effect is less pronounced for large clusters. Our results show
an early appearance of nonplanar ground-state geometries and it is obs
erved that for n greater than or equal to 6 the Al atom gets trapped i
nside the Na cage. The stability of these clusters has been examined f
rom the systematic analysis of energetics. This indicates Na5Al and Na
7Al having 8 and 10 valence electrons to be the stable clusters.