First-principles studies of Cu clusters

Equilibrium geometries and electronic properties of neutral and anionic Cu_n (n = 2, 10) clusters are determined via first-principles calculations which treat s and d electrons on an equal footing. We find cluster shapes similar to those reported in the literature for Na_n clusters, but the highly coordinated structures are energetically preferred. Electronic states with atomic s character are strongly hybridized with d states and located mostly at the band edges. Angular decomposition of the electronic wave functions shows that the predictions of the shell model are followed only approximately in Cu_n clusters. Finally we interpret successfully the photoelectron spectrum of Cu^-₃ by accounting for final-state effects.