Ca(NiO2)2 crystallizes in the orthorhombic Pbcm space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. Ni(1) is bonded to one O(3), two equivalent O(2), and three equivalent O(1) atoms to form a mixture of distorted edge and corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 14-48°. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ca(1) and three equivalent Ni(1) atoms to form distorted OCa2Ni3 square pyramids that share corners with four equivalent O(2)Ca2Ni4 octahedra, corners with two equivalent O(1)Ca2Ni3 square pyramids, corners with five equivalent O(3)Ca2Ni2 tetrahedra, edges with three equivalent O(2)Ca2Ni4 octahedra, edges with five equivalent O(1)Ca2Ni3 square pyramids, and  an edgeedge with one O(3)Ca2Ni2 tetrahedra. The corner-sharing octahedral tilt angles range from 6-49°. In the second O site, O(2) is bonded to two equivalent Ca(1) and four equivalent Ni(1) atoms to form distorted OCa2Ni4 octahedra that share corners with two equivalent O(2)Ca2Ni4 octahedra, corners with eight equivalent O(1)Ca2Ni3 square pyramids, edges with two equivalent O(2)Ca2Ni4 octahedra, edges with six equivalent O(1)Ca2Ni3 square pyramids, and edges with four equivalent O(3)Ca2Ni2 tetrahedra. The corner-sharing octahedral tilt angles are 47°. In the third O site, O(3) is bonded to two equivalent Ca(1) and two equivalent Ni(1) atoms to form distorted OCa2Ni2 tetrahedra that share corners with ten equivalent O(1)Ca2Ni3 square pyramids, corners with two equivalent O(3)Ca2Ni2 tetrahedra, edges with four equivalent O(2)Ca2Ni4 octahedra, and edges with two equivalent O(1)Ca2Ni3 square pyramids.
Ca(NiO2)2 crystallizes in the orthorhombic Pbcm space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. Both Ca(1)-O(2) bond lengths are 2.60 Å. Both Ca(1)-O(3) bond lengths are 2.26 Å. There are two shorter (2.39 Å) and two longer (2.47 Å) Ca(1)-O(1) bond lengths. Ni(1) is bonded to one O(3), two equivalent O(2), and three equivalent O(1) atoms to form a mixture of distorted edge and corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 14-48°. The Ni(1)-O(3) bond length is 1.89 Å. There is one shorter (1.95 Å) and one longer (2.49 Å) Ni(1)-O(2) bond length. There are a spread of Ni(1)-O(1) bond distances ranging from 1.89-2.21 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ca(1) and three equivalent Ni(1) atoms to form distorted OCa2Ni3 square pyramids that share corners with four equivalent O(2)Ca2Ni4 octahedra, corners with two equivalent O(1)Ca2Ni3 square pyramids, corners with five equivalent O(3)Ca2Ni2 tetrahedra, edges with three equivalent O(2)Ca2Ni4 octahedra, edges with five equivalent O(1)Ca2Ni3 square pyramids, and  an edgeedge with one O(3)Ca2Ni2 tetrahedra. The corner-sharing octahedral tilt angles range from 6-49°. In the second O site, O(2) is bonded to two equivalent Ca(1) and four equivalent Ni(1) atoms to form distorted OCa2Ni4 octahedra that share corners with two equivalent O(2)Ca2Ni4 octahedra, corners with eight equivalent O(1)Ca2Ni3 square pyramids, edges with two equivalent O(2)Ca2Ni4 octahedra, edges with six equivalent O(1)Ca2Ni3 square pyramids, and edges with four equivalent O(3)Ca2Ni2 tetrahedra. The corner-sharing octahedral tilt angles are 47°. In the third O site, O(3) is bonded to two equivalent Ca(1) and two equivalent Ni(1) atoms to form distorted OCa2Ni2 tetrahedra that share corners with ten equivalent O(1)Ca2Ni3 square pyramids, corners with two equivalent O(3)Ca2Ni2 tetrahedra, edges with four equivalent O(2)Ca2Ni4 octahedra, and edges with two equivalent O(1)Ca2Ni3 square pyramids.