Theoretical Investigation of Ta2O5, TaON, and Ta3N5: Electronic Band Structures and Absolute Band Edges

Abstract

Early transition metal oxides, nitrides, and oxynitrides have attracted a great deal of interest because of their potential applications in photovoltaics and photocatalysis. In this work, a systematic investigation is conducted of the electronic band structures of the Ta2O5 polymorphs, β-Ta3N5 and β-TaON, which are crucial for the understanding of their photocatalytic properties, based on state-of-the-art first-principles approaches. The calculated results imply that many-body perturbation theory in the GW approximation can overcome the severe underestimation of the band gap caused by standard density functional theory (DFT) in the local and semilocal approximations and provide a quantitative agreement with experiment. The effects of the electron–phonon coupling on the electronic band structure are considered by the Frolich model, and especially for ϵ-Ta2O5, a strong electron–phonon coupling is predicted as a result of small high-frequency dielectric constants and large effective masses. Based on an analy...