Ca(NiO2)2 is Spinel structured and crystallizes in the triclinic P-1 space group. Ca(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form CaO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra, corners with three equivalent Ni(2)O6 octahedra, corners with three equivalent Ni(3)O6 octahedra, and corners with three equivalent Ni(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-70°. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted NiO6 octahedra that share corners with six equivalent Ca(1)O4 tetrahedra, edges with two equivalent Ni(2)O6 octahedra, edges with two equivalent Ni(3)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. In the second Ni site, Ni(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with six equivalent Ca(1)O4 tetrahedra, edges with two equivalent Ni(1)O6 octahedra, edges with two equivalent Ni(3)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. In the third Ni site, Ni(3) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted NiO6 octahedra that share corners with six equivalent Ca(1)O4 tetrahedra, edges with two equivalent Ni(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. In the fourth Ni site, Ni(4) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted NiO6 octahedra that share corners with six equivalent Ca(1)O4 tetrahedra, edges with two equivalent Ni(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with two equivalent Ni(3)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ni(1), one Ni(3), and one Ni(4) atom to form a mixture of distorted edge and corner-sharing OCaNi3 tetrahedra. In the second O site, O(2) is bonded to one Ca(1), one Ni(1), one Ni(2), and one Ni(4) atom to form a mixture of distorted edge and corner-sharing OCaNi3 tetrahedra. In the third O site, O(3) is bonded to one Ca(1), one Ni(1), one Ni(2), and one Ni(3) atom to form a mixture of distorted edge and corner-sharing OCaNi3 trigonal pyramids. In the fourth O site, O(4) is bonded to one Ca(1), one Ni(2), one Ni(3), and one Ni(4) atom to form a mixture of distorted edge and corner-sharing OCaNi3 trigonal pyramids.
Ca(NiO2)2 is Spinel structured and crystallizes in the triclinic P-1 space group. Ca(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form CaO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra, corners with three equivalent Ni(2)O6 octahedra, corners with three equivalent Ni(3)O6 octahedra, and corners with three equivalent Ni(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-70°. The Ca(1)-O(1) bond length is 2.18 Å. The Ca(1)-O(2) bond length is 2.19 Å. The Ca(1)-O(3) bond length is 2.18 Å. The Ca(1)-O(4) bond length is 2.19 Å. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted NiO6 octahedra that share corners with six equivalent Ca(1)O4 tetrahedra, edges with two equivalent Ni(2)O6 octahedra, edges with two equivalent Ni(3)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. Both Ni(1)-O(1) bond lengths are 1.92 Å. Both Ni(1)-O(2) bond lengths are 1.90 Å. Both Ni(1)-O(3) bond lengths are 2.28 Å. In the second Ni site, Ni(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with six equivalent Ca(1)O4 tetrahedra, edges with two equivalent Ni(1)O6 octahedra, edges with two equivalent Ni(3)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. Both Ni(2)-O(2) bond lengths are 2.22 Å. Both Ni(2)-O(3) bond lengths are 1.90 Å. Both Ni(2)-O(4) bond lengths are 1.93 Å. In the third Ni site, Ni(3) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted NiO6 octahedra that share corners with six equivalent Ca(1)O4 tetrahedra, edges with two equivalent Ni(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. Both Ni(3)-O(1) bond lengths are 1.90 Å. Both Ni(3)-O(3) bond lengths are 1.92 Å. Both Ni(3)-O(4) bond lengths are 2.26 Å. In the fourth Ni site, Ni(4) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted NiO6 octahedra that share corners with six equivalent Ca(1)O4 tetrahedra, edges with two equivalent Ni(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with two equivalent Ni(3)O6 octahedra. Both Ni(4)-O(1) bond lengths are 2.24 Å. Both Ni(4)-O(2) bond lengths are 1.93 Å. Both Ni(4)-O(4) bond lengths are 1.90 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ni(1), one Ni(3), and one Ni(4) atom to form a mixture of distorted edge and corner-sharing OCaNi3 tetrahedra. In the second O site, O(2) is bonded to one Ca(1), one Ni(1), one Ni(2), and one Ni(4) atom to form a mixture of distorted edge and corner-sharing OCaNi3 tetrahedra. In the third O site, O(3) is bonded to one Ca(1), one Ni(1), one Ni(2), and one Ni(3) atom to form a mixture of distorted edge and corner-sharing OCaNi3 trigonal pyramids. In the fourth O site, O(4) is bonded to one Ca(1), one Ni(2), one Ni(3), and one Ni(4) atom to form a mixture of distorted edge and corner-sharing OCaNi3 trigonal pyramids.