Materials Data on MgNiO2 by Materials Project
MgNiO2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to five O2- atoms to form MgO5 trigonal bipyramids that share corners with four equivalent MgO4 tetrahedra, corners with two equivalent NiO5 trigonal bipyramids, edges with two equivalent MgO5 trigonal bipyramids, and a faceface with one NiO5 trigonal bipyramid. There are three shorter (2.04 Å) and two longer (2.11 Å) Mg–O bond lengths. In the second Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with two equivalent MgO4 tetrahedra, corners with four equivalent MgO5 trigonal bipyramids, corners with four equivalent NiO5 trigonal bipyramids, and an edgeedge with one NiO5 trigonal bipyramid. There are a spread of Mg–O bond distances ranging from 1.95–1.99 Å. There are two inequivalent Ni2+ sites. In the first Ni2+ site, Ni2+ is bonded in a rectangular see-saw-like geometry to four O2- atoms. There is two shorter (1.89 Å) and two longer (2.03 Å) Ni–O bond length. In the second Ni2+ site, Ni2+ is bonded to five O2- atoms to form distorted NiO5 trigonal bipyramids that share corners with four equivalent MgO4 tetrahedra, corners with two equivalent MgO5 trigonal bipyramids, an edgeedge with one MgO4 tetrahedra, edges with two equivalent NiO5 trigonal bipyramids, and a faceface with one MgO5 trigonal bipyramid. There are a spread of Ni–O bond distances ranging from 2.02–2.18 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+ and three Ni2+ atoms to form distorted OMgNi3 tetrahedra that share corners with two equivalent OMgNi3 tetrahedra, corners with four equivalent OMg3Ni2 trigonal bipyramids, and an edgeedge with one OMg3Ni2 trigonal bipyramid. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to two equivalent Mg2+ and two equivalent Ni2+ atoms. In the third O2- site, O2- is bonded to three Mg2+ and two equivalent Ni2+ atoms to form distorted OMg3Ni2 trigonal bipyramids that share corners with four equivalent OMgNi3 tetrahedra, an edgeedge with one OMgNi3 tetrahedra, and edges with two equivalent OMg3Ni2 trigonal bipyramids. In the fourth O2- site, O2- is bonded in a 5-coordinate geometry to three Mg2+ and two equivalent Ni2+ atoms.