Structures and electronic properties of stoichiometric hydrogenated aluminum clusters

The lowest-energy geometries and electronic-structure properties have been obtained for AlnHn (n=1-10) clusters within the density-functional theory using the generalized gradient approximation for the exchange correlation potential. The resulting geometries show that the hydrogen atoms tend to occupy outside positions and no hollow positions are found. The subunit Aln of AlnHn (n=1-5) have little distortion, in comparison with corresponding pure Aln cluster, whereas the subunit Aln have large distortion from n=6. The stability has been investigated by analyzing the binding energy per atom and the second difference in energy, indicating that Al8H8 exhibit higher stability than others. The bonding property has been analyzed by calculating the Mulliken charges and Al–H distances. The calculated energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO-LUMO), the vertical ionization potential, and the vertical electron affinity also confirm that Al8H8 is a stable cluster. The density of states (DOS) shows that AlnHn exhibit changes from molecular-like (Al1H1) to band-like structure (Al10H10) as n increases