Effect of Cr substitution on the electronic structure of CuAl1−xCrxO2

The geometries and electronic structures of CuAl1−xCrxO2 have been investigated using density-functional theory with on-site corrections for strongly correlated systems GGA+U for x=0, 1 2 ,1. Al is found to be well described within the ionic model, with a valence charge corresponding to a +3 oxidation state. Substituting Cr for Al is predicted to increase the density of states at the top of the valence band, in agreement with experimental x-ray photoemission spectroscopy data. Analysis of atom-projected densities of states and valence charges suggests that this is due to increased covalency between Cr and O; the valence charge for O in the Cu-OAl,Cr subunits changes from −1.74 to −1.25 when Cr replaces Al. This produces an indirect oxygenmediated change to the Cu d states.