Ground-state geometries and stability of Na<SUB>n</SUB>Mg (n=1-2) clusters using ab initio molecular dynamics method

The ground-state geometries, energetics and the stability of NanMg (n=1-12) clusters are studied using ab initio molecular dynamics method. Our results indicate that the ground-state geometries of large clusters ( n &#8805; 6) are different from those of NanAL clusters where a trivalent impurity Al is added to the same monovalent host Na. Other features observed are an early appearance of 3-dimensional structure and a pentagonal growth path from n=6 up to n=11. As expected, the ground-state geometry of Na12Mg is not an icosahedron but can be viewed as a distorted form of one of the low lying geometries of Na13 cluster. In the energetically favored structures impurity atom Mg is never located at the center of the cluster. The stability analysis based on the energetics shows Na6Mg (8 valence electrons) to be the most stable. In addition there is a remarkable even-odd pattern observed in the dissociation energy and the second difference in energy which is absent in earlier studies of NanAL and LinAl clusters