Stability and magic numbers of hetero-atomic clusters of simple metals

The main trends in the magic numbers observed for a class of simple-metal hetero-atomic clusters M_xN (M = Na or K; N = monovalent or divalent impurity; X = number of host atoms) is explained using an extension of the jellium model of clusters. The appearance of a “new” magic number, n = 10 (n = number of valence electrons), and the growing importance of n = 20 over n = 18, as Δ₊ increases (Δ₊ is the difference in the density of the jellium backgrounds of the two metals) are explained by an inversion of the order of the energy levels with respect to that of pure clusters.