Study of Electronic and Thermoelectric Properties of CaNiO₃ Perovskite

Perovskite structured materials find a wide range of technological application, from solar cells, to catalysts, and thermoelectricity. In this study, we investigate the electronic, magnetic, and thermoelectric properties of CaNiO₃, a transition metal perovskite, using all-electron and pseudopotential density-functional-theory. Both meta-GGA and ACBN0 functional predict that the ground state of CaNiO₃ is orthorhombic with a narrow bandgap of E_g~0.3-0.5 eV. The predicted absence of magnetism is consistent with a Ni⁺⁴ oxidation state, as well as the observed opening of a bandgap. In contrast, our ACBN0 computations predict that cubic CaNiO₃ is a ferromagnetic metal. Thus, our preliminary results show that the bandgap opening, and disappearance of magnetism is caused by the continuous octahedral rotations that connect the cubic and orthorhombic structure. The meta-GGA computations predict thermoelectric figure of merit of CaNiO₃, ZT=1.08 at 300K, 66% larger than that of double perovskite CaPd₃B₄O₁₂ (B = Ti, V) reported previously. At T=1200 K, we find ZT=0.57, comparable to other thermoelectric materials. Therefore, our results predict that CaNiO₃ is an excellent candidate for thermoelectric applications at room temperature as well as high temperatures.