Ground-state geometries and stability of NanMg (n=1-12) 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 r esults indicate that the ground-state geometries of large clusters (n great er than or equal to 6) are different from those of NanAl clusters where a t rivalent impurity Al is added to the same monovalent host Na. Other feature s observed are an early appearance of 3-dimensional structure and a pentago nal growth path from n = 6 up to n = 11. As expected, the ground-state geom etry of Na12Mg is not an icosahedron but can be viewed as a distorted form of one of the low lying geometries of Na-13 cluster. In the energetically f avored structures impurity atom Mg is never located at the center of the cl uster. The stability analysis based on the energetics shows Na6Mg (8 valenc e electrons) to be the most stable. In addition there is a remarkable even- odd pattern observed in the dissociation energy and the second difference i n energy which is absent in earlier studies of NanAl and LinAl clusters.