Materials Data on Mg3Ni2O7 by Materials Project
Mg3Ni2O7 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Mg–O bond distances ranging from 2.06–2.28 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form distorted MgO6 octahedra that share corners with two equivalent NiO6 octahedra, corners with eight equivalent MgO6 octahedra, edges with two equivalent NiO6 octahedra, and a faceface with one NiO6 octahedra. The corner-sharing octahedra tilt angles range from 43–75°. There are a spread of Mg–O bond distances ranging from 2.00–2.32 Å. Ni4+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with five equivalent NiO6 octahedra, edges with two equivalent MgO6 octahedra, and a faceface with one MgO6 octahedra. The corner-sharing octahedra tilt angles range from 39–62°. There are a spread of Ni–O bond distances ranging from 1.87–1.94 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to three equivalent Mg2+ and one Ni4+ atom to form distorted OMg3Ni tetrahedra that share corners with six equivalent OMg3Ni tetrahedra and a cornercorner with one OMg2Ni2 trigonal pyramid. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Mg2+ and two equivalent Ni4+ atoms. In the third O2- site, O2- is bonded in a 5-coordinate geometry to three Mg2+ and two equivalent Ni4+ atoms. In the fourth O2- site, O2- is bonded to two equivalent Mg2+ and two equivalent Ni4+ atoms to form distorted OMg2Ni2 trigonal pyramids that share corners with two equivalent OMg3Ni tetrahedra and corners with two equivalent OMg2Ni2 trigonal pyramids.