DFT study of the fragmentation channels and electronic properties of Cu ^ν_n (ν= ±1,0,2; n=3-13) clusters

Abstract

We report a theoretical study on small copper clusters Cu ^ν_n (ν= ±1,0,2; n=3-13). We have published the optimized geometries in a previous paper, obtained with a gradient embedded genetic algorithm (GEGA) technique, and further density functional theory (DFT) geometry reoptimization of the best GEGA cluster structures for each size and charge. For the lower energy isomers of these clusters, we report in this paper the total all-electron energies and electronic properties such as the adiabatic ionization potentials, electron affinities, global hardnesses, and binding energies. Furthermore, we compute for each possible fragmentation channels of cationic copper clusters, the involved energetics, ΔE, and the extended-hardness change, Δη, based on the maximum hardness principle of Pearson and Chattaraj, Lee, and Parr, within the conceptual DFT formalism, but where η is computed with adiabatic rather than vertical energies. Both methods are shown to be in very good agreement with most available experimental findings. We argue that extended-hardness and the extended-hardness change are good DFT descriptors to assess the preferred fragmentation channels of charged copper clusters, where formation of the hardest fragments seems to be the driving force. Our theoretical results suggest that relaxation in these species is perhaps faster than usually assumed in the experiments performed to measure their fragmentation.