Ca(Ni2O3)2 crystallizes in the orthorhombic Cmcm space group. Ca(1) is bonded in a 6-coordinate geometry to two equivalent O(4) and four equivalent O(2) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), two equivalent O(1), and three equivalent O(3) atoms to form a mixture of edge and corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-8°. In the second Ni site, Ni(2) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form a mixture of edge and corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-46°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ni(2) and four equivalent Ni(1) atoms to form ONi6 octahedra that share corners with four equivalent O(3)Ni5 square pyramids, corners with two equivalent O(4)Ca2Ni2 tetrahedra, edges with two equivalent O(1)Ni6 octahedra, edges with six equivalent O(3)Ni5 square pyramids, and edges with four equivalent O(2)Ca2Ni3 trigonal bipyramids. In the second O site, O(2) is bonded to two equivalent Ca(1), one Ni(1), and two equivalent Ni(2) atoms to form distorted OCa2Ni3 trigonal bipyramids that share corners with five equivalent O(3)Ni5 square pyramids, corners with four equivalent O(4)Ca2Ni2 tetrahedra, corners with two equivalent O(2)Ca2Ni3 trigonal bipyramids, edges with two equivalent O(1)Ni6 octahedra,  an edgeedge with one O(3)Ni5 square pyramid,  an edgeedge with one O(4)Ca2Ni2 tetrahedra, and edges with three equivalent O(2)Ca2Ni3 trigonal bipyramids. In the third O site, O(3) is bonded to two equivalent Ni(2) and three equivalent Ni(1) atoms to form distorted ONi5 square pyramids that share corners with two equivalent O(1)Ni6 octahedra, corners with two equivalent O(4)Ca2Ni2 tetrahedra, corners with five equivalent O(2)Ca2Ni3 trigonal bipyramids, edges with three equivalent O(1)Ni6 octahedra, edges with four equivalent O(3)Ni5 square pyramids, and  an edgeedge with one O(2)Ca2Ni3 trigonal bipyramid. The corner-sharing octahedral tilt angles are 3°. In the fourth O site, O(4) is bonded to two equivalent Ca(1) and two equivalent Ni(2) atoms to form distorted OCa2Ni2 tetrahedra that share corners with two equivalent O(1)Ni6 octahedra, corners with four equivalent O(3)Ni5 square pyramids, corners with two equivalent O(4)Ca2Ni2 tetrahedra, corners with eight equivalent O(2)Ca2Ni3 trigonal bipyramids, and edges with two equivalent O(2)Ca2Ni3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 1°.
Ca(Ni2O3)2 crystallizes in the orthorhombic Cmcm space group. Ca(1) is bonded in a 6-coordinate geometry to two equivalent O(4) and four equivalent O(2) atoms. Both Ca(1)-O(4) bond lengths are 2.28 Å. All Ca(1)-O(2) bond lengths are 2.38 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), two equivalent O(1), and three equivalent O(3) atoms to form a mixture of edge and corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-8°. The Ni(1)-O(2) bond length is 1.91 Å. Both Ni(1)-O(1) bond lengths are 2.12 Å. There is one shorter (1.98 Å) and two longer (2.10 Å) Ni(1)-O(3) bond lengths. In the second Ni site, Ni(2) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form a mixture of edge and corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-46°. The Ni(2)-O(1) bond length is 2.16 Å. The Ni(2)-O(4) bond length is 1.96 Å. Both Ni(2)-O(2) bond lengths are 2.03 Å. Both Ni(2)-O(3) bond lengths are 2.16 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ni(2) and four equivalent Ni(1) atoms to form ONi6 octahedra that share corners with four equivalent O(3)Ni5 square pyramids, corners with two equivalent O(4)Ca2Ni2 tetrahedra, edges with two equivalent O(1)Ni6 octahedra, edges with six equivalent O(3)Ni5 square pyramids, and edges with four equivalent O(2)Ca2Ni3 trigonal bipyramids. In the second O site, O(2) is bonded to two equivalent Ca(1), one Ni(1), and two equivalent Ni(2) atoms to form distorted OCa2Ni3 trigonal bipyramids that share corners with five equivalent O(3)Ni5 square pyramids, corners with four equivalent O(4)Ca2Ni2 tetrahedra, corners with two equivalent O(2)Ca2Ni3 trigonal bipyramids, edges with two equivalent O(1)Ni6 octahedra,  an edgeedge with one O(3)Ni5 square pyramid,  an edgeedge with one O(4)Ca2Ni2 tetrahedra, and edges with three equivalent O(2)Ca2Ni3 trigonal bipyramids. In the third O site, O(3) is bonded to two equivalent Ni(2) and three equivalent Ni(1) atoms to form distorted ONi5 square pyramids that share corners with two equivalent O(1)Ni6 octahedra, corners with two equivalent O(4)Ca2Ni2 tetrahedra, corners with five equivalent O(2)Ca2Ni3 trigonal bipyramids, edges with three equivalent O(1)Ni6 octahedra, edges with four equivalent O(3)Ni5 square pyramids, and  an edgeedge with one O(2)Ca2Ni3 trigonal bipyramid. The corner-sharing octahedral tilt angles are 3°. In the fourth O site, O(4) is bonded to two equivalent Ca(1) and two equivalent Ni(2) atoms to form distorted OCa2Ni2 tetrahedra that share corners with two equivalent O(1)Ni6 octahedra, corners with four equivalent O(3)Ni5 square pyramids, corners with two equivalent O(4)Ca2Ni2 tetrahedra, corners with eight equivalent O(2)Ca2Ni3 trigonal bipyramids, and edges with two equivalent O(2)Ca2Ni3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 1°.