Materials Data on CaNi3O7 by Materials Project
CaNi3O7 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ca2+ is bonded to seven O2- atoms to form distorted CaO7 pentagonal bipyramids that share corners with seven NiO5 trigonal bipyramids and edges with four NiO5 trigonal bipyramids. There are a spread of Ca–O bond distances ranging from 2.31–2.46 Å. There are two inequivalent Ni4+ sites. In the first Ni4+ site, Ni4+ is bonded to five O2- atoms to form distorted NiO5 trigonal bipyramids that share corners with three equivalent CaO7 pentagonal bipyramids, corners with two equivalent NiO5 trigonal bipyramids, an edgeedge with one CaO7 pentagonal bipyramid, and edges with three NiO5 trigonal bipyramids. There are a spread of Ni–O bond distances ranging from 1.79–1.98 Å. In the second Ni4+ site, Ni4+ is bonded to five O2- atoms to form distorted NiO5 trigonal bipyramids that share a cornercorner with one CaO7 pentagonal bipyramid, corners with four equivalent NiO5 trigonal bipyramids, edges with two equivalent CaO7 pentagonal bipyramids, and edges with two equivalent NiO5 trigonal bipyramids. There are a spread of Ni–O bond distances ranging from 1.89–1.92 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ca2+ and one Ni4+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ca2+ and one Ni4+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+ and three Ni4+ atoms. In the fourth O2- site, O2- is bonded in a distorted see-saw-like geometry to one Ca2+ and three Ni4+ atoms.