Effect of strain on the optical properties of LaNiO3: A first-principle study

Optical properties of the pseudo-cubic lanthanum nickel oxide (LaNiO3) have been investigated using first-principle density-functional theory under unstrained and strained condition. To incorporate the effect of strong electron correlation in LaNiO3, the generalized gradient approximation + Hubbard U (GGA+ U) approach is used. Electronic structure and the optical properties of pure LaNiO3, namely optical conductivity, refractive index, dielectric function and the reflectance have been studied in detail. The non-vanishing density of states at the Fermi level are found to come from the strong hybridization between Ni 3d and O 2p orbitals, which ascertain the metallic nature of LaNiO3. The optical conductivity spectra have a dominant Drude contribution at low energy, and the high energy region is governed by several inter-band transitions. The changes in the optical properties on application of in-plane tensile and compressive strains are ascribed to the altered electronic structure of the system. Our observation reveals that systems under both tensile and compressive strains are metallic albeit strongly correlated. However LaNiO3 under tensile strain is more strongly correlated than under compressive strain. (C) 2015 Elsevier B.V. All rights reserved.