A quantum-mechanical investigation of oxygen vacancies and copper doping in the orthorhombic CaSnO₃perovskite

Abstract

In this study we explore the implications of oxygen vacancy formation and of copper doping in the orthorhombic CaSnO3 perovskite, by means of density functional theory, focusing on energetic and electronic properties. In particular, the electronic charge distribution is analyzed by Mulliken, Hirshfeld-I, Bader and Wannier approaches. Calculations are performed at the PBE and the PBE0 level (for doping with Cu, only PBE0), with both spin-restricted and spin-unrestricted formulations; unrestricted calculations are used for spin-polarized cases and for the naturally open-shell cases (Cu doping). An oxygen vacancy is found to have the tendency to reduce Sn neighbors by giving rise to an energy band within the energy band-gap of the pristine system, close to the valence band. At variance with what happens in the CaTiO3 perovskite (also investigated here), an oxygen vacancy in the CaSnO3 perovskite is found to lose two valence electrons and thus to be positively charged so that no F-center is formed. Regarding Cu doping, when one Sn atom is substituted by a Cu one, the most stable configuration corresponds to having the Cu atom as a first neighbor to the vacancy. These findings shed some light on the catalytic and phosphorous host properties of this perovskite.

Uncovering the Origin of the Emitting States in Bi3+-Activated CaMO3 (M = Zr, Sn, Ti) Perovskites: Metal-To-Metal Charge Transfer Versus s–p Transitions

“…Because of the charge-transfer nature of the emitting state that is strongly related to the CB bottom of the host, a temperature dependence linked to the band gap behavior is expected. Density functional theory calculations of the density of states (DOS) of CaSnO 3 and CaTiO 3 have demonstrated that the bottom of the CB is mainly formed by the 6s, 6p-Sn orbitals and the 3d-Ti orbitals, respectively. In this context, the temperature dependence of the band gap is usually characterized by a red shift by increasing the temperature, − and a consequent red shift is expected for the MMCT emission band, raising the temperature.…”

Computational procedure to an accurate DFT simulation to solid state systems

“…Nevertheless, the B3LYP functional was also used to perform the simulations for the sake of comparison with the WC1LYP, because it is one of the most used functional to study crystalline materials. 50 Although the results have been somewhat favorable, they can still be improved. The preliminary structural and electronic results of both paths are described below.…”

Light Harvesting from Oxygen Vacancies and A- and B-Site Dopants in CaSnO3 Perovskite through Efficient Photon Utilization and Local Site Engineering

“…Perovskites are considered one of the most investigated materials for a variety of applications owing to their unique electronic, optical, magnetic, catalytic, and ferroelectric properties. ,, Among perovskites, CaSnO 3 (CSO), a high band gap semiconductor with a band gap of ∼4.7 eV is considered a highly diverse oxide owing to its unique structure, properties, and multifunctional applications. These included optoelectronics, catalysis, sensors, photodetectors, phosphors, lithium-ion batteries, and so forth. ,− Defects such as antisites, Schottky, oxygen vacancies (OVs), and so forth are abundantly present in CSO and are reported to have significant influence on its optical, catalytic, magnetic, and electrical properties. − These defects can also lead to interesting photoluminescence properties in CSO as well, which is an extremely important area of research in these days for designing dopant- and lattice strain-free phosphors . Each defect has a specific role and can be engineered to achieve specific applications.…”