Materials Data on Ca2Ni3O8 by Materials Project

Abstract

Ca2Ni3O8 is Pyrite-derived structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Ca2+ is bonded to six O2- atoms to form distorted CaO6 pentagonal pyramids that share corners with seven NiO6 octahedra, edges with three NiO6 octahedra, and edges with two equivalent CaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 21–56°. There are a spread of Ca–O bond distances ranging from 2.25–2.42 Å. There are two inequivalent Ni4+ sites. In the first Ni4+ site, Ni4+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with six equivalent CaO6 pentagonal pyramids, edges with four equivalent NiO6 octahedra, and edges with two equivalent CaO6 pentagonal pyramids. There is four shorter (1.88 Å) and two longer (1.90 Å) Ni–O bond length. In the second Ni4+ site, Ni4+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with four equivalent CaO6 pentagonal pyramids, edges with four NiO6 octahedra, and edges with two equivalent CaO6 pentagonal pyramids. There are a spread of Ni–O bond distances ranging from 1.86–1.95 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+ and two equivalent Ni4+ atoms. In the second O2- site, O2- is bonded to one Ca2+ and three Ni4+ atoms to form a mixture of distorted edge and corner-sharing OCaNi3 trigonal pyramids. In the third O2- site, O2- is bonded to two equivalent Ca2+ and two Ni4+ atoms to form a mixture of distorted edge and corner-sharing OCa2Ni2 trigonal pyramids.