AlH3 and Al2H6:: Magic clusters with unmagical properties

Enhanced stability, low electron affinity, and high ionization potential are the hallmarks of a "magic" cluster. With an electron affinity of 0.28 eV, ionization potential of 11.43 eV, and a large binding energy, AlH3 satisfies these criteria. However, unlike other magic clusters that interact only weakly with each other, two AlH3 clusters bind to each other with an energy of 1.54 eV. The resulting Al2H6, while also a magic cluster in its own light, possesses the most unusual property that the difference between its adiabatic and vertical detachment energy is about 2 eV-the largest of any known cluster. These results, based on density functional theory, are verified experimentally through photodetachment spectroscopy. DOI: 10.1103/PhvsRevLett.86.692.