Theory of the copper vacancy in cuprous oxide

Density-functional theory is used to examine aspects of the copper vacancy (VCu) in cuprous oxide (Cu2O). The normal vacancy configuration, obtained by simple removal of a Cu atom from the lattice, is found to be 0.1 eV higher in energy than a split vacancy configuration wherein a nearby Cu atom is displaced toward a normal vacancy site by half the bulk Cu–Cu separation. Jumps between the normal and split vacancy configurations are predicted to be rate limiting for VCu diffusion with an energy barrier of 0.3 eV. Binding of VCu to substitutional aluminum (AlCu) and indium (InCu) is examined. The neutral (AlCu+2VCu) complex is found to have a binding energy of 3.3 eV whereas the neutral (InCu+2VCu) complex is bound by 1.7 eV. The magnitudes of these binding energies suggest that AlCu and InCu should inhibit VCu diffusion in Cu2O.