DOE OSTI2020
Mg(NiO2)2 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine NiO6 octahedra. The corner-sharing octahedra tilt angles range from 54–63°. There are a spread of Mg–O bond distances ranging from 1.96–2.00 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three NiO4 tetrahedra, and edges with six NiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.03–2.06 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine NiO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There are a spread of Mg–O bond distances ranging from 1.96–2.00 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four NiO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five NiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.02–2.06 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six NiO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent NiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.03–2.07 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six NiO4 tetrahedra, edges with two MgO6 octahedra, and edges with four NiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.08 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five NiO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five NiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.02–2.07 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six NiO4 tetrahedra, edges with two MgO6 octahedra, and edges with four NiO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.02–2.07 Å. There are twelve inequivalent Ni3+ sites. In the first Ni3+ site, Ni3+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with three MgO4 tetrahedra, corners with three NiO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four NiO6 octahedra. There are a spread of Ni–O bond distances ranging from 1.90–2.06 Å. In the second Ni3+ site, Ni3+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent NiO4 tetrahedra, edges with two MgO6 octahedra, and edges with four NiO6 octahedra. There are a spread of Ni–O bond distances ranging from 1.91–2.06 Å. In the third Ni3+ site, Ni3+ is bonded to four O2- atoms to form NiO4 tetrahedra that share corners with six MgO6 octahedra and corners with six NiO6 octahedra. The corner-sharing octahedra tilt angles range from 54–59°. There is two shorter (1.88 Å) and two longer (1.90 Å) Ni–O bond length. In the fourth Ni3+ site, Ni3+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four NiO4 tetrahedra, edges with three MgO6 octahedra, and edges with three NiO6 octahedra. There are a spread of Ni–O bond distances ranging from 1.87–2.02 Å. In the fifth Ni3+ site, Ni3+ is bonded to four O2- atoms to form NiO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine NiO6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There are a spread of Ni–O bond distances ranging from 1.89–1.94 Å. In the sixth Ni3+ site, Ni3+ is bonded to four O2- atoms to form NiO4 tetrahedra that share corners with six MgO6 octahedra and corners with six NiO6 octahedra. The corner-sharing octahedra tilt angles range from 53–59°. There are a spread of Ni–O bond distances ranging from 1.83–1.88 Å. In the seventh Ni3+ site, Ni3+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with six NiO4 tetrahedra, edges with two equivalent NiO6 octahedra, and edges with four MgO6 octahedra. There are a spread of Ni–O bond distances ranging from 1.87–2.02 Å. In the eighth Ni3+ site, Ni3+ is bonded to four O2- atoms to form NiO4 tetrahedra that share corners with six MgO6 octahedra and corners with six NiO6 octahedra. The corner-sharing octahedra tilt angles range from 54–62°. There is three shorter (1.91 Å) and one longer (1.93 Å) Ni–O bond length. In the ninth Ni3+ site, Ni3+ is bonded to six O2- atoms to form NiO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five NiO4 tetrahedra, edges with three MgO6 octahedra, and edges with three NiO6 octahedra. There are a spread of Ni–O bond distances ranging from 1.91–2.10 Å. In the tenth Ni3+ site, Ni3+ is bonded to four O2- atoms to form NiO4 tetrahedra that share corners with six MgO6 octahedra and corners with six NiO6 octahedra. The corner-sharing octahedra tilt angles range from 56–63°. There are a spread of Ni–O bond distances ranging from 1.90–2.02 Å. In the eleventh Ni3+ site, Ni3+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent NiO4 tetrahedra, edges with two MgO6 octahedra, and edges with four NiO6 octahedra. There are a spread of Ni–O bond distances ranging from 1.87–1.91 Å. In the twelfth Ni3+ site, Ni3+ is bonded to four O2- atoms to form NiO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine NiO6 octahedra. The corner-sharing octahedra tilt angles range from 49–62°. There is two shorter (1.96 Å) and two longer (1.98 Å) Ni–O bond length. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded to two Mg2+ and two Ni3+ atoms to form distorted OMg2Ni2 trigonal pyramids that share a cornercorner with one OMg2Ni2 tetrahedra, corners with five OMgNi3 trigonal pyramids, and an edgeedge with one OMg2Ni2 trigonal pyramid. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two equivalent Ni3+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Ni3+ atoms. In the fifth O2- site, O2- is bonded to two Mg2+ and two Ni3+ atoms to form a mixture of distorted corner and edge-sharing OMg2Ni2 trigonal pyramids. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the eighth O2- site, O2- is bonded to one Mg2+ and three Ni3+ atoms to form distorted corner-sharing OMgNi3 trigonal pyramids. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the tenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Ni3+ atoms. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the twelfth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Ni3+ atoms. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the fourteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the sixteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the seventeenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Ni3+ atoms. In the eighteenth O2- site, O2- is bonded to two Mg2+ and two Ni3+ atoms to form a mixture of distorted corner and edge-sharing OMg2Ni2 trigonal pyramids. In the nineteenth O2- site, O2- is bonded to two Mg2+ and two equivalent Ni3+ atoms to form distorted corner-sharing OMg2Ni2 tetrahedra. In the twentieth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the twenty-first O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms. In the twenty-second O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Ni3+ atoms. In the twenty-third O2- site, O2- is bonded to one Mg2+ and three Ni3+ atoms to form distorted OMgNi3 trigonal pyramids that share corners with two equivalent OMg2Ni2 tetrahedra, corners with four OMgNi3 trigonal pyramids, and an edgeedge with one OMgNi3 trigonal pyramid. In the twenty-fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ni3+ atoms.