Electronic Band Structures of ATaO3(A = Li, Na, and K) from First-Principles Many-Body Perturbation Theory

Abstract

Alkaline tantalates, ATaO3 (A = Li, Na, and K), have attracted a lot of interest in recent years due to their interesting photocatalytic properties and their photocatalytic activity is influenced by a lot of factors, making them ideal model systems for in-depth theoretical investigation. In this work, electronic band structures of alkaline tantalates are investigated based on first-principles many-body perturbation theory in the GW approximation. The band gaps of NaTaO3 and KTaO3 from the GW approach agree very well with experiment; on the other hand, the band gap of LiTaO3 from GW is significantly larger than the experimental values. A strong dependence on crystal structures is observed in LiTaO3, whose band gap in the cubic and rhombohedral structure differs by more than 1.5 eV. Combined with the phenomenological ionic model, it is found that both the Madelung potential and the bandwidth can have strong influences on the band gap. By comparing the structure dependence of LiTaO3 and NaTaO3, it is conclud...