Mg(NiO2)2 is Spinel-like structured and crystallizes in the trigonal P3m1 space group. There are six inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(10) and three equivalent O(1) atoms to form MgO4 tetrahedra that share corners with three equivalent Mg(3)O6 octahedra, corners with three equivalent Ni(4)O6 octahedra, and corners with six equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 58-62°. In the second Mg site, Mg(2) is bonded to one O(2) and three equivalent O(4) atoms to form MgO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra, corners with three equivalent Ni(3)O6 octahedra, and corners with six equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-60°. In the third Mg site, Mg(3) is bonded to three equivalent O(1) and three equivalent O(11) atoms to form MgO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Ni(6)O4 tetrahedra, edges with three equivalent Ni(1)O6 octahedra, and edges with three equivalent Ni(4)O6 octahedra. In the fourth Mg site, Mg(4) is bonded to one O(6) and three equivalent O(8) atoms to form MgO4 tetrahedra that share corners with three equivalent Ni(2)O6 octahedra, corners with three equivalent Ni(5)O6 octahedra, and corners with six equivalent Ni(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 57-59°. In the fifth Mg site, Mg(5) is bonded to one O(9) and three equivalent O(3) atoms to form MgO4 tetrahedra that share corners with three equivalent Ni(2)O6 octahedra, corners with three equivalent Ni(3)O6 octahedra, and corners with six equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 58-62°. In the sixth Mg site, Mg(6) is bonded to one O(12) and three equivalent O(7) atoms to form MgO4 tetrahedra that share corners with three equivalent Ni(4)O6 octahedra, corners with three equivalent Ni(5)O6 octahedra, and corners with six equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-60°. There are six inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(5), two equivalent O(1), and two equivalent O(3) atoms to form NiO6 octahedra that share  a cornercorner with one Mg(2)O4 tetrahedra,  a cornercorner with one Ni(6)O4 tetrahedra, corners with two equivalent Mg(1)O4 tetrahedra, corners with two equivalent Mg(5)O4 tetrahedra,  an edgeedge with one Mg(3)O6 octahedra,  an edgeedge with one Ni(3)O6 octahedra, and edges with four equivalent Ni(1)O6 octahedra. In the second Ni site, Ni(2) is bonded to one O(6), one O(9), two equivalent O(4), and two equivalent O(7) atoms to form NiO6 octahedra that share  a cornercorner with one Mg(4)O4 tetrahedra,  a cornercorner with one Mg(5)O4 tetrahedra, corners with two equivalent Mg(2)O4 tetrahedra, corners with two equivalent Mg(6)O4 tetrahedra,  an edgeedge with one Ni(3)O6 octahedra,  an edgeedge with one Ni(5)O6 octahedra, and edges with four equivalent Ni(2)O6 octahedra. In the third Ni site, Ni(3) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form NiO6 octahedra that share corners with three equivalent Mg(2)O4 tetrahedra, corners with three equivalent Mg(5)O4 tetrahedra, edges with three equivalent Ni(1)O6 octahedra, and edges with three equivalent Ni(2)O6 octahedra. In the fourth Ni site, Ni(4) is bonded to one O(10), one O(12), two equivalent O(11), and two equivalent O(8) atoms to form NiO6 octahedra that share  a cornercorner with one Mg(1)O4 tetrahedra,  a cornercorner with one Mg(6)O4 tetrahedra, corners with two equivalent Mg(4)O4 tetrahedra, corners with two equivalent Ni(6)O4 tetrahedra,  an edgeedge with one Mg(3)O6 octahedra,  an edgeedge with one Ni(5)O6 octahedra, and edges with four equivalent Ni(4)O6 octahedra. In the fifth Ni site, Ni(5) is bonded to three equivalent O(7) and three equivalent O(8) atoms to form NiO6 octahedra that share corners with three equivalent Mg(4)O4 tetrahedra, corners with three equivalent Mg(6)O4 tetrahedra, edges with three equivalent Ni(2)O6 octahedra, and edges with three equivalent Ni(4)O6 octahedra. In the sixth Ni site, Ni(6) is bonded to one O(5) and three equivalent O(11) atoms to form NiO4 tetrahedra that share corners with three equivalent Mg(3)O6 octahedra, corners with three equivalent Ni(1)O6 octahedra, and corners with six equivalent Ni(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-58°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Mg(3), and two equivalent Ni(1) atoms to form distorted OMg2Ni2 trigonal pyramids that share corners with four equivalent O(3)MgNi3 tetrahedra,  a cornercorner with one O(10)MgNi3 trigonal pyramid, corners with two equivalent O(1)Mg2Ni2 trigonal pyramids, and edges with two equivalent O(1)Mg2Ni2 trigonal pyramids. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(2) and three equivalent Ni(1) atoms. In the third O site, O(3) is bonded to one Mg(5), one Ni(3), and two equivalent Ni(1) atoms to form distorted OMgNi3 tetrahedra that share corners with two equivalent O(3)MgNi3 tetrahedra,  a cornercorner with one O(9)MgNi3 trigonal pyramid, corners with three equivalent O(4)MgNi3 trigonal pyramids, corners with four equivalent O(1)Mg2Ni2 trigonal pyramids, and edges with two equivalent O(3)MgNi3 tetrahedra. In the fourth O site, O(4) is bonded to one Mg(2), one Ni(3), and two equivalent Ni(2) atoms to form a mixture of distorted edge and corner-sharing OMgNi3 trigonal pyramids. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Ni(6) and three equivalent Ni(1) atoms. In the sixth O site, O(6) is bonded to one Mg(4) and three equivalent Ni(2) atoms to form a mixture of distorted edge and corner-sharing OMgNi3 trigonal pyramids. In the seventh O site, O(7) is bonded to one Mg(6), one Ni(5), and two equivalent Ni(2) atoms to form a mixture of distorted edge and corner-sharing OMgNi3 trigonal pyramids. In the eighth O site, O(8) is bonded to one Mg(4), one Ni(5), and two equivalent Ni(4) atoms to form a mixture of distorted edge and corner-sharing OMgNi3 trigonal pyramids. In the ninth O site, O(9) is bonded to one Mg(5) and three equivalent Ni(2) atoms to form a mixture of distorted edge and corner-sharing OMgNi3 trigonal pyramids. In the tenth O site, O(10) is bonded to one Mg(1) and three equivalent Ni(4) atoms to form distorted OMgNi3 trigonal pyramids that share corners with three equivalent O(12)MgNi3 tetrahedra, corners with three equivalent O(1)Mg2Ni2 trigonal pyramids, and edges with three equivalent O(8)MgNi3 trigonal pyramids. In the eleventh O site, O(11) is bonded in a rectangular see-saw-like geometry to one Mg(3), one Ni(6), and two equivalent Ni(4) atoms. In the twelfth O site, O(12) is bonded to one Mg(6) and three equivalent Ni(4) atoms to form distorted corner-sharing OMgNi3 tetrahedra.
Mg(NiO2)2 is Spinel-like structured and crystallizes in the trigonal P3m1 space group. There are six inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(10) and three equivalent O(1) atoms to form MgO4 tetrahedra that share corners with three equivalent Mg(3)O6 octahedra, corners with three equivalent Ni(4)O6 octahedra, and corners with six equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 58-62°. The Mg(1)-O(10) bond length is 2.02 Å. All Mg(1)-O(1) bond lengths are 1.98 Å. In the second Mg site, Mg(2) is bonded to one O(2) and three equivalent O(4) atoms to form MgO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra, corners with three equivalent Ni(3)O6 octahedra, and corners with six equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-60°. The Mg(2)-O(2) bond length is 1.95 Å. All Mg(2)-O(4) bond lengths are 1.95 Å. In the third Mg site, Mg(3) is bonded to three equivalent O(1) and three equivalent O(11) atoms to form MgO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Ni(6)O4 tetrahedra, edges with three equivalent Ni(1)O6 octahedra, and edges with three equivalent Ni(4)O6 octahedra. All Mg(3)-O(1) bond lengths are 2.06 Å. All Mg(3)-O(11) bond lengths are 2.09 Å. In the fourth Mg site, Mg(4) is bonded to one O(6) and three equivalent O(8) atoms to form MgO4 tetrahedra that share corners with three equivalent Ni(2)O6 octahedra, corners with three equivalent Ni(5)O6 octahedra, and corners with six equivalent Ni(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 57-59°. The Mg(4)-O(6) bond length is 1.98 Å. All Mg(4)-O(8) bond lengths are 1.96 Å. In the fifth Mg site, Mg(5) is bonded to one O(9) and three equivalent O(3) atoms to form MgO4 tetrahedra that share corners with three equivalent Ni(2)O6 octahedra, corners with three equivalent Ni(3)O6 octahedra, and corners with six equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 58-62°. The Mg(5)-O(9) bond length is 2.01 Å. All Mg(5)-O(3) bond lengths are 2.00 Å. In the sixth Mg site, Mg(6) is bonded to one O(12) and three equivalent O(7) atoms to form MgO4 tetrahedra that share corners with three equivalent Ni(4)O6 octahedra, corners with three equivalent Ni(5)O6 octahedra, and corners with six equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-60°. The Mg(6)-O(12) bond length is 1.98 Å. All Mg(6)-O(7) bond lengths are 2.01 Å. There are six inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(5), two equivalent O(1), and two equivalent O(3) atoms to form NiO6 octahedra that share  a cornercorner with one Mg(2)O4 tetrahedra,  a cornercorner with one Ni(6)O4 tetrahedra, corners with two equivalent Mg(1)O4 tetrahedra, corners with two equivalent Mg(5)O4 tetrahedra,  an edgeedge with one Mg(3)O6 octahedra,  an edgeedge with one Ni(3)O6 octahedra, and edges with four equivalent Ni(1)O6 octahedra. The Ni(1)-O(2) bond length is 2.03 Å. The Ni(1)-O(5) bond length is 2.09 Å. Both Ni(1)-O(1) bond lengths are 1.92 Å. Both Ni(1)-O(3) bond lengths are 1.93 Å. In the second Ni site, Ni(2) is bonded to one O(6), one O(9), two equivalent O(4), and two equivalent O(7) atoms to form NiO6 octahedra that share  a cornercorner with one Mg(4)O4 tetrahedra,  a cornercorner with one Mg(5)O4 tetrahedra, corners with two equivalent Mg(2)O4 tetrahedra, corners with two equivalent Mg(6)O4 tetrahedra,  an edgeedge with one Ni(3)O6 octahedra,  an edgeedge with one Ni(5)O6 octahedra, and edges with four equivalent Ni(2)O6 octahedra. The Ni(2)-O(6) bond length is 1.99 Å. The Ni(2)-O(9) bond length is 2.01 Å. Both Ni(2)-O(4) bond lengths are 1.97 Å. Both Ni(2)-O(7) bond lengths are 1.99 Å. In the third Ni site, Ni(3) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form NiO6 octahedra that share corners with three equivalent Mg(2)O4 tetrahedra, corners with three equivalent Mg(5)O4 tetrahedra, edges with three equivalent Ni(1)O6 octahedra, and edges with three equivalent Ni(2)O6 octahedra. All Ni(3)-O(3) bond lengths are 2.03 Å. All Ni(3)-O(4) bond lengths are 2.05 Å. In the fourth Ni site, Ni(4) is bonded to one O(10), one O(12), two equivalent O(11), and two equivalent O(8) atoms to form NiO6 octahedra that share  a cornercorner with one Mg(1)O4 tetrahedra,  a cornercorner with one Mg(6)O4 tetrahedra, corners with two equivalent Mg(4)O4 tetrahedra, corners with two equivalent Ni(6)O4 tetrahedra,  an edgeedge with one Mg(3)O6 octahedra,  an edgeedge with one Ni(5)O6 octahedra, and edges with four equivalent Ni(4)O6 octahedra. The Ni(4)-O(10) bond length is 1.98 Å. The Ni(4)-O(12) bond length is 1.99 Å. Both Ni(4)-O(11) bond lengths are 2.03 Å. Both Ni(4)-O(8) bond lengths are 2.00 Å. In the fifth Ni site, Ni(5) is bonded to three equivalent O(7) and three equivalent O(8) atoms to form NiO6 octahedra that share corners with three equivalent Mg(4)O4 tetrahedra, corners with three equivalent Mg(6)O4 tetrahedra, edges with three equivalent Ni(2)O6 octahedra, and edges with three equivalent Ni(4)O6 octahedra. All Ni(5)-O(7) bond lengths are 1.94 Å. All Ni(5)-O(8) bond lengths are 1.97 Å. In the sixth Ni site, Ni(6) is bonded to one O(5) and three equivalent O(11) atoms to form NiO4 tetrahedra that share corners with three equivalent Mg(3)O6 octahedra, corners with three equivalent Ni(1)O6 octahedra, and corners with six equivalent Ni(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-58°. The Ni(6)-O(5) bond length is 1.86 Å. All Ni(6)-O(11) bond lengths are 1.87 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Mg(3), and two equivalent Ni(1) atoms to form distorted OMg2Ni2 trigonal pyramids that share corners with four equivalent O(3)MgNi3 tetrahedra,  a cornercorner with one O(10)MgNi3 trigonal pyramid, corners with two equivalent O(1)Mg2Ni2 trigonal pyramids, and edges with two equivalent O(1)Mg2Ni2 trigonal pyramids. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(2) and three equivalent Ni(1) atoms. In the third O site, O(3) is bonded to one Mg(5), one Ni(3), and two equivalent Ni(1) atoms to form distorted OMgNi3 tetrahedra that share corners with two equivalent O(3)MgNi3 tetrahedra,  a cornercorner with one O(9)MgNi3 trigonal pyramid, corners with three equivalent O(4)MgNi3 trigonal pyramids, corners with four equivalent O(1)Mg2Ni2 trigonal pyramids, and edges with two equivalent O(3)MgNi3 tetrahedra. In the fourth O site, O(4) is bonded to one Mg(2), one Ni(3), and two equivalent Ni(2) atoms to form a mixture of distorted edge and corner-sharing OMgNi3 trigonal pyramids. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Ni(6) and three equivalent Ni(1) atoms. In the sixth O site, O(6) is bonded to one Mg(4) and three equivalent Ni(2) atoms to form a mixture of distorted edge and corner-sharing OMgNi3 trigonal pyramids. In the seventh O site, O(7) is bonded to one Mg(6), one Ni(5), and two equivalent Ni(2) atoms to form a mixture of distorted edge and corner-sharing OMgNi3 trigonal pyramids. In the eighth O site, O(8) is bonded to one Mg(4), one Ni(5), and two equivalent Ni(4) atoms to form a mixture of distorted edge and corner-sharing OMgNi3 trigonal pyramids. In the ninth O site, O(9) is bonded to one Mg(5) and three equivalent Ni(2) atoms to form a mixture of distorted edge and corner-sharing OMgNi3 trigonal pyramids. In the tenth O site, O(10) is bonded to one Mg(1) and three equivalent Ni(4) atoms to form distorted OMgNi3 trigonal pyramids that share corners with three equivalent O(12)MgNi3 tetrahedra, corners with three equivalent O(1)Mg2Ni2 trigonal pyramids, and edges with three equivalent O(8)MgNi3 trigonal pyramids. In the eleventh O site, O(11) is bonded in a rectangular see-saw-like geometry to one Mg(3), one Ni(6), and two equivalent Ni(4) atoms. In the twelfth O site, O(12) is bonded to one Mg(6) and three equivalent Ni(4) atoms to form distorted corner-sharing OMgNi3 tetrahedra.