First-Principles Study of Intrinsic Point Defects and Optical Properties of SmNiO3

Defects are closely related to the optical properties and metal-to-insulator phase transition in SmNiO3 (SNO) and therefore play an important role in their applications. In this paper, the intrinsic point defects were studied in both stoichiometric and nonstoichiometric SNO by first-principles calculations. In stoichiometric SNO, the Schottky defects composed of nominally charged Sm, Ni, and O vacancies are the most stable existence. In nonstoichiometric SNO, excess Sm2O3 (or Sm) creates the formation of O vacancies and Ni vacancies and Sm-Ni antisite defects, while Ni-Sm antisite defects form in an excess Ni2O3 (or Ni and NiO) environment. Oxygen vacancies affect electronic structures by introducing additional electrons, leading to the formation of an occupied Ni-O state in SNO. Moreover, the calculations of optical properties show that the O vacancies increase the transmittance in the visible light region, while the Ni interstitials decrease transmittance within visible light and infrared light regions. This work provides a coherent picture of native point defects and optical properties in SNO, which have implications for the current experimental work on rare-earth nickelates compounds.