Reduced forms of LaNiO3 perovskite. Part 2.—X-ray structure of LaNiO2 and extended X-ray absorption fine structure study: local environment of monovalent nickel

Abstract

One of the products of the reduction of LaNiO₃ is LaNiO₂, containing monovalent nickel. This valence state of nickel has scarcely been observed in mineral compounds. X-ray data from powder samples and extended X-ray absorption fine structure studies (EXAFS) allow one to define a tetragonal structure with lanthanum at the centre of a prism composed of oxygen atoms having a square base and nickel in the centre of the square. The Ni—O distance (nearest neighbour) was found to be 1.983 Å for this monovalent nickel.