Comparison of electronic structure of LiInO 2 with NaInO 2

Abstract

Electronic structure of NaCl type LiInO 2 was compared experimentally and theoretically with that of α-NaFeO 2 type NaInO 2 to clarify the influences of Li–In direct interaction peculiar to LiInO 2. Ultraviolet–visible diffuse reflectance spectrum of LiInO 2, with the onset of absorption at 3.7 eV, was rather more simple than that of NaInO 2 accompanied by two small peaks in the band gap of 3.7 eV. Discrete variational-Xα calculations for the [Li 10In 9O 44] 51− and [Na 7In 12O 44] 45− model clusters depicted well the features of absorption spectra of LiInO 2 and α-NaInO 2, respectively. The calculations also revealed that higher valence bands of LiInO 2 and NaInO 2 were dominated, respectively, by the Li 2s–In 5s bonding orbital with a large overlap population and the Na 3s,p–O 2p bonding orbital with a small overlap population, however, lower conduction bands in both LiInO 2 and NaInO 2 were formed by the In 5s–O 2p antibonding orbital. The experimental valence band spectrum of LiInO 2, simply peaked at ∼4 eV below the valence band maximum, can be ascribed to overlapping of the Li 2s–In 5s bonding orbital with the In 5p–O 2p bonding orbital at around −3 eV in the density of states.