Ionization potential of aluminum clusters

Structure, electronic structure, and ionization potential of aluminum clusters of 2--23 atoms are studied with a total energy method based on the density-functional theory. The calculated adiabatic ionization potentials agree remarkably well with the data from threshold photoionization measurements. The analysis of results gives insight into hybridization effects in the smallest clusters as well as reveals certain clusters that exhibit a clear jellium-type shell structure. An explanation of the experimental results in the size region of 12--23 atoms is given in terms of coexisting, competing icosahedral, decahedral, and fcc-based clusters.