STABILITY OF NANPB (N-LESS-THAN-OR-EQUAL-TO-7) CLUSTERS - A FIRST-PRINCIPLES MOLECULAR-DYNAMICS STUDY

The structural and electronic properties of bimetallic clusters NanPb (n less than or equal to 7) are calculated by means of a first-princip les molecular-dynamics simulated annealing, using the local-density ap proximation and the pseudopotential plane-wave method. We obtain that the observed exceptional abundance of Na6Pb in molecular beams is due to the combination of electronic and geometrical factors, which are ab sent in the case of n not equal 6 clusters. In particular, we find tha t adding another Na atom to Na6Pb is energetically less favorable than adding it to a pure Na cluster, in contrast to what we obtain for sma ller NanPb clusters.