FIRST-PRINCIPLES CALCULATIONS OF THE THERMODYNAMICAL STABILITY OF REDUCED NDNIO3-X OXIDES

Work package:
Context: The study of oxygen-deficient perovskites is an active and fast-growing field of research which may allow the discovery of functional materials potentially interesting for a wide range of applications [1]. A revival of the interest for nickelates has recently emerged due to the major breakthrough in condensed matter with the finding of a superconducting state in infinite square-planar lattices [2]. RNiO3 perovskites have stimulated several experimental and theoretical research efforts because of their rich phase diagrams including different crystallographic phases associated with metallic / insulating and paramagnetic / antiferromagnetic states. Owing to their strong electronic correlations, their tunable atomic structures and their rich properties, Ni-based perovskites are thus already promising for memristive and neuromorphic applications [3, 4]. Goals: During this internship, we propose to calculate numerically the physical properties (atomic and electronic structure, spin and orbital magnetic moments) of NdNiO3 bulk oxide. We will then study the thermodynamical stability of reduced phases NdNiO3-x (0 < x <1) as a function of the distribution of oxygen vacancies and of structural strain. The main goal of this internship will be to understand the intricate link between the atomic distortions in the newly generated structural phases and the induced modifications of the reference properties [5] calculated for the perfect crystal. Ab initio numerical calculations of the electronic structure will be performed using the density functional theory (DFT). During the internship, a few code developments may be needed for the post-processing of generated data.