The group 14 cationic clusters by encapsulation of coinage metals X10M+, with X = Ge, Sn, Pb and M = Cu, Ag, Au: Enhanced stability of 40 valence electron systems

The coinage metal encapsulated group 14 cationic clusters X10M+ (X = Ge, Sn, Pb and M = Cu, Ag, Au) are investigated using quantum chemical calculations. While Cu- and Au-doped clusters have similar stability, Ag-doped counterparts are less stable. The D4d global minima have large frontier orbital gaps and binding energies, and are magic clusters of 40 valence electrons that satisfy the jellium shell model. The concept of doubly spherical aromaticity, based on the number of 2(N + 1)2 π and σ valence electrons, is proposed to account for the enhanced stability. Predictions are in good agreement with experiment for available X10Cu+ clusters.