Bulk and surface properties of the Ruddlesden-Popper oxynitride Sr₂TaO₃N

Oxynitrides with the perovskite structure are promising candidates for photocatalysis under visible light due to their appropriate optical and electronic properties. Recently, layered perovskites have attracted attention for their improved performance with respect to bulk perovskites in photocatalytic water splitting. In this paper, we investigate the structural and electronic properties of the layered Ruddlesden-Popper oxynitride Sr₂TaO₃N and its (001) and (100) surfaces using density functional theory (DFT) calculations. We find that the energetically favoured configuration of the bulk has an in-plane cis anion order and exhibits rotations of the TaON octahedra. Furthermore, we show that the TaON-terminated (001) surface suppresses exciton recombination due to higher-energy surface states, giving a potential explanation for the good photocatalytic performance.