Color and conductivity in Cu2O and CuAlO2: A theoretical analysis of d(10)center dot center dot center dot d(10) interactions in solid-state compounds

The influence of homoatomic d(10)...d(10) interactions in the structural an d physical properties of some copper-containing oxides has been investigate d by using semiempirical band structure calculations of the extended Huckel type. Comparison of the band structures of CuAlO2 and Cu2O, two compounds with Cu(I) ions in practically identical coordination environments, reveals that the spatial arrangement of Cu Cu contacts is responsible for their ma rkedly different electrical and optical properties. The three-dimensional n et of short Cu...Cu distances present in Cu2O is found to be essential for the appearance of color in this p-type semiconductor. In doped CuAlO2, on t he contrary, the 2-D nature of the array of Cu...Cu contacts leads to optic al transparency and a lower conductivity if compared to cuprite.