Magic Rule for ${\mathrm{Al}}_n{\mathrm{H}}_m$ Magic Clusters

Using the electronic shell closure criteria, we propose a new electron counting rule that enables us to predict the size, composition, and structure of many hitherto unknown magic clusters consisting of hydrogen and aluminum atoms. This rule, whose validity is established through a synergy between first-principles calculations and anion-photoelectron spectroscopy experiments, provides a powerful basis for searching magic clusters consisting of hydrogen and simple metal atoms.

Figure 1

Computed geometries of two low lying isomers of representative ${\mathrm{Al}}_n{\mathrm{H}}_m$ ($n>m$) clusters along with their relative energies (eV).

Figure 2

Computed geometries of two low lying isomers of ${\mathrm{Al}}_n\mathrm{H}_m{}^{-}$ clusters. The relative energies and the ADE (in italics) are given in eV.

Figure 3

Photoelectron spectra of (a) ${\mathrm{Al}}_7{\mathrm{H}}^{-}$ and (b) ${\mathrm{Al}}_8\mathrm{H}_4{}^{-}$. Estimated HOMO-LUMO gaps of the corresponding neutrals are marked with horizontal arrows.