Lowest-Energy Structures and Electronic Properties of Al-n(-) Clusters (n=2-35) from Ab Initio Genetic Algorithm Search

摘要

Genetic algorithm combined with density functional theory (DFT) calculations is used to explore the size evolution of structural and electronic properties of anionic aluminum cluster (Al-n(-) with n = 2-35) in terms of their ground-state structures, binding energies, second order differences of total energies, HOMO-LUMO gaps, and photoelectron spectra. The lowest-energy structures of smallest Al-5(-) clusters (n <= 5) are planar, while three dimensional configurations dominate for n >= 6. The icosahedron of Al-13(-) and double icosahedrons of Al-19(-) are found as the core for the growth motif of aluminum clusters. For n = 20-24, a competition between double icosahedrons and fragments of fcc crystal is found. As the cluster size exceeds 25, the lowest-energy structures tend to adopt layered structure with fcc-like packing. We also simulated photoelectron spectra and vertical detach energies of Al-n(-) and reproduced the experimental data rather well, confirming the reliability of our theoretical results.