Ca(NiO2)2 is Spinel-like structured and crystallizes in the monoclinic Cm space group. There are six inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(13), one O(3), and two equivalent O(1) atoms to form CaO4 tetrahedra that share  a cornercorner with one Ca(6)O6 octahedra, corners with two equivalent Ca(3)O6 octahedra, corners with two equivalent Ni(6)O6 octahedra, corners with three equivalent Ni(3)O6 octahedra, and corners with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-75°. In the second Ca site, Ca(2) is bonded to one O(5), one O(9), two equivalent O(4), and two equivalent O(7) atoms to form CaO6 octahedra that share corners with three equivalent Ni(2)O4 tetrahedra, corners with three equivalent Ni(7)O4 tetrahedra,  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(5)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. In the third Ca site, Ca(3) is bonded to one O(2), one O(8), two equivalent O(1), and two equivalent O(7) atoms to form CaO6 octahedra that share  a cornercorner with one Ni(2)O4 tetrahedra,  a cornercorner with one Ni(9)O4 tetrahedra, corners with two equivalent Ca(1)O4 tetrahedra, corners with two equivalent Ni(7)O4 tetrahedra,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Ni(3)O6 octahedra, and edges with four equivalent Ni(1)O6 octahedra. In the fourth Ca site, Ca(4) is bonded to one O(11), one O(15), two equivalent O(10), and two equivalent O(12) atoms to form CaO6 octahedra that share corners with three equivalent Ni(5)O4 tetrahedra, corners with three equivalent Ni(8)O4 tetrahedra,  an edgeedge with one Ca(5)O6 octahedra,  an edgeedge with one Ca(6)O6 octahedra, edges with two equivalent Ni(4)O6 octahedra, and edges with two equivalent Ni(6)O6 octahedra. In the fifth Ca site, Ca(5) is bonded to one O(14), one O(6), two equivalent O(12), and two equivalent O(4) atoms to form CaO6 octahedra that share  a cornercorner with one Ni(5)O4 tetrahedra,  a cornercorner with one Ni(7)O4 tetrahedra, corners with two equivalent Ni(2)O4 tetrahedra, corners with two equivalent Ni(8)O4 tetrahedra,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Ca(4)O6 octahedra, and edges with four equivalent Ni(4)O6 octahedra. In the sixth Ca site, Ca(6) is bonded to one O(13), one O(18), two equivalent O(10), and two equivalent O(17) atoms to form CaO6 octahedra that share  a cornercorner with one Ca(1)O4 tetrahedra,  a cornercorner with one Ni(8)O4 tetrahedra, corners with two equivalent Ni(5)O4 tetrahedra, corners with two equivalent Ni(9)O4 tetrahedra,  an edgeedge with one Ca(4)O6 octahedra,  an edgeedge with one Ni(3)O6 octahedra, and edges with four equivalent Ni(6)O6 octahedra. There are nine inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(7), and one O(8) atom to form NiO6 octahedra that share  a cornercorner with one Ni(2)O4 tetrahedra,  a cornercorner with one Ni(9)O4 tetrahedra, corners with two equivalent Ca(1)O4 tetrahedra, corners with two equivalent Ni(7)O4 tetrahedra,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Ni(3)O6 octahedra, edges with two equivalent Ca(3)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. In the second Ni site, Ni(2) is bonded to one O(2), one O(9), and two equivalent O(4) atoms to form NiO4 tetrahedra that share  a cornercorner with one Ca(3)O6 octahedra, corners with two equivalent Ca(5)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, corners with three equivalent Ca(2)O6 octahedra, and corners with four equivalent Ni(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-61°. In the third Ni site, Ni(3) is bonded to one O(16), one O(3), two equivalent O(1), and two equivalent O(17) atoms to form NiO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Ni(9)O4 tetrahedra,  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(6)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(6)O6 octahedra. In the fourth Ni site, Ni(4) is bonded to one O(11), one O(12), one O(14), one O(4), one O(6), and one O(9) atom to form NiO6 octahedra that share  a cornercorner with one Ni(5)O4 tetrahedra,  a cornercorner with one Ni(7)O4 tetrahedra, corners with two equivalent Ni(2)O4 tetrahedra, corners with two equivalent Ni(8)O4 tetrahedra,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Ca(4)O6 octahedra, edges with two equivalent Ca(5)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. In the fifth Ni site, Ni(5) is bonded to one O(15), one O(6), and two equivalent O(10) atoms to form NiO4 tetrahedra that share  a cornercorner with one Ca(5)O6 octahedra, corners with two equivalent Ca(6)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra, corners with three equivalent Ca(4)O6 octahedra, and corners with four equivalent Ni(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-64°. In the sixth Ni site, Ni(6) is bonded to one O(10), one O(13), one O(15), one O(16), one O(17), and one O(18) atom to form NiO6 octahedra that share  a cornercorner with one Ca(1)O4 tetrahedra,  a cornercorner with one Ni(8)O4 tetrahedra, corners with two equivalent Ni(5)O4 tetrahedra, corners with two equivalent Ni(9)O4 tetrahedra,  an edgeedge with one Ca(4)O6 octahedra,  an edgeedge with one Ni(3)O6 octahedra, edges with two equivalent Ca(6)O6 octahedra, and edges with two equivalent Ni(6)O6 octahedra. In the seventh Ni site, Ni(7) is bonded to one O(14), one O(5), and two equivalent O(7) atoms to form NiO4 tetrahedra that share  a cornercorner with one Ca(5)O6 octahedra, corners with two equivalent Ca(3)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra, corners with three equivalent Ca(2)O6 octahedra, and corners with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-67°. In the eighth Ni site, Ni(8) is bonded to one O(11), one O(18), and two equivalent O(12) atoms to form NiO4 tetrahedra that share  a cornercorner with one Ca(6)O6 octahedra, corners with two equivalent Ca(5)O6 octahedra, corners with two equivalent Ni(6)O6 octahedra, corners with three equivalent Ca(4)O6 octahedra, and corners with four equivalent Ni(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-69°. In the ninth Ni site, Ni(9) is bonded to one O(16), one O(8), and two equivalent O(17) atoms to form NiO4 tetrahedra that share  a cornercorner with one Ca(3)O6 octahedra, corners with two equivalent Ca(6)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, corners with three equivalent Ni(3)O6 octahedra, and corners with four equivalent Ni(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-66°. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ca(3), one Ni(1), and one Ni(3) atom to form distorted OCa2Ni2 tetrahedra that share  a cornercorner with one O(1)Ca2Ni2 tetrahedra,  a cornercorner with one O(13)Ca2Ni2 tetrahedra,  a cornercorner with one O(3)CaNi3 trigonal pyramid, corners with two equivalent O(8)CaNi3 trigonal pyramids,  an edgeedge with one O(1)Ca2Ni2 tetrahedra, and  an edgeedge with one O(3)CaNi3 trigonal pyramid. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Ca(3), one Ni(2), and two equivalent Ni(1) atoms. In the third O site, O(3) is bonded to one Ca(1), one Ni(3), and two equivalent Ni(1) atoms to form distorted OCaNi3 trigonal pyramids that share  a cornercorner with one O(13)Ca2Ni2 tetrahedra, corners with two equivalent O(1)Ca2Ni2 tetrahedra, corners with two equivalent O(8)CaNi3 trigonal pyramids, and edges with two equivalent O(1)Ca2Ni2 tetrahedra. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Ca(2), one Ca(5), one Ni(2), and one Ni(4) atom. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Ca(2), one Ni(7), and two equivalent Ni(1) atoms. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Ca(5), one Ni(5), and two equivalent Ni(4) atoms. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to one Ca(2), one Ca(3), one Ni(1), and one Ni(7) atom. In the eighth O site, O(8) is bonded to one Ca(3), one Ni(9), and two equivalent Ni(1) atoms to form distorted OCaNi3 trigonal pyramids that share corners with four equivalent O(1)Ca2Ni2 tetrahedra and corners with two equivalent O(3)CaNi3 trigonal pyramids. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to one Ca(2), one Ni(2), and two equivalent Ni(4) atoms. In the tenth O site, O(10) is bonded in a rectangular see-saw-like geometry to one Ca(4), one Ca(6), one Ni(5), and one Ni(6) atom. In the eleventh O site, O(11) is bonded in a rectangular see-saw-like geometry to one Ca(4), one Ni(8), and two equivalent Ni(4) atoms. In the twelfth O site, O(12) is bonded in a rectangular see-saw-like geometry to one Ca(4), one Ca(5), one Ni(4), and one Ni(8) atom. In the thirteenth O site, O(13) is bonded to one Ca(1), one Ca(6), and two equivalent Ni(6) atoms to form distorted OCa2Ni2 tetrahedra that share corners with two equivalent O(1)Ca2Ni2 tetrahedra and  a cornercorner with one O(3)CaNi3 trigonal pyramid. In the fourteenth O site, O(14) is bonded in a rectangular see-saw-like geometry to one Ca(5), one Ni(7), and two equivalent Ni(4) atoms. In the fifteenth O site, O(15) is bonded in a distorted rectangular see-saw-like geometry to one Ca(4), one Ni(5), and two equivalent Ni(6) atoms. In the sixteenth O site, O(16) is bonded in a rectangular see-saw-like geometry to one Ni(3), one Ni(9), and two equivalent Ni(6) atoms. In the seventeenth O site, O(17) is bonded in a rectangular see-saw-like geometry to one Ca(6), one Ni(3), one Ni(6), and one Ni(9) atom. In the eighteenth O site, O(18) is bonded in a rectangular see-saw-like geometry to one Ca(6), one Ni(8), and two equivalent Ni(6) atoms.
Ca(NiO2)2 is Spinel-like structured and crystallizes in the monoclinic Cm space group. There are six inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(13), one O(3), and two equivalent O(1) atoms to form CaO4 tetrahedra that share  a cornercorner with one Ca(6)O6 octahedra, corners with two equivalent Ca(3)O6 octahedra, corners with two equivalent Ni(6)O6 octahedra, corners with three equivalent Ni(3)O6 octahedra, and corners with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-75°. The Ca(1)-O(13) bond length is 2.21 Å. The Ca(1)-O(3) bond length is 2.31 Å. Both Ca(1)-O(1) bond lengths are 2.16 Å. In the second Ca site, Ca(2) is bonded to one O(5), one O(9), two equivalent O(4), and two equivalent O(7) atoms to form CaO6 octahedra that share corners with three equivalent Ni(2)O4 tetrahedra, corners with three equivalent Ni(7)O4 tetrahedra,  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(5)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. The Ca(2)-O(5) bond length is 2.33 Å. The Ca(2)-O(9) bond length is 2.32 Å. Both Ca(2)-O(4) bond lengths are 2.26 Å. Both Ca(2)-O(7) bond lengths are 2.27 Å. In the third Ca site, Ca(3) is bonded to one O(2), one O(8), two equivalent O(1), and two equivalent O(7) atoms to form CaO6 octahedra that share  a cornercorner with one Ni(2)O4 tetrahedra,  a cornercorner with one Ni(9)O4 tetrahedra, corners with two equivalent Ca(1)O4 tetrahedra, corners with two equivalent Ni(7)O4 tetrahedra,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Ni(3)O6 octahedra, and edges with four equivalent Ni(1)O6 octahedra. The Ca(3)-O(2) bond length is 2.28 Å. The Ca(3)-O(8) bond length is 2.28 Å. Both Ca(3)-O(1) bond lengths are 2.24 Å. Both Ca(3)-O(7) bond lengths are 2.22 Å. In the fourth Ca site, Ca(4) is bonded to one O(11), one O(15), two equivalent O(10), and two equivalent O(12) atoms to form CaO6 octahedra that share corners with three equivalent Ni(5)O4 tetrahedra, corners with three equivalent Ni(8)O4 tetrahedra,  an edgeedge with one Ca(5)O6 octahedra,  an edgeedge with one Ca(6)O6 octahedra, edges with two equivalent Ni(4)O6 octahedra, and edges with two equivalent Ni(6)O6 octahedra. The Ca(4)-O(11) bond length is 2.31 Å. The Ca(4)-O(15) bond length is 2.31 Å. Both Ca(4)-O(10) bond lengths are 2.26 Å. Both Ca(4)-O(12) bond lengths are 2.24 Å. In the fifth Ca site, Ca(5) is bonded to one O(14), one O(6), two equivalent O(12), and two equivalent O(4) atoms to form CaO6 octahedra that share  a cornercorner with one Ni(5)O4 tetrahedra,  a cornercorner with one Ni(7)O4 tetrahedra, corners with two equivalent Ni(2)O4 tetrahedra, corners with two equivalent Ni(8)O4 tetrahedra,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Ca(4)O6 octahedra, and edges with four equivalent Ni(4)O6 octahedra. The Ca(5)-O(14) bond length is 2.30 Å. The Ca(5)-O(6) bond length is 2.29 Å. Both Ca(5)-O(12) bond lengths are 2.24 Å. Both Ca(5)-O(4) bond lengths are 2.25 Å. In the sixth Ca site, Ca(6) is bonded to one O(13), one O(18), two equivalent O(10), and two equivalent O(17) atoms to form CaO6 octahedra that share  a cornercorner with one Ca(1)O4 tetrahedra,  a cornercorner with one Ni(8)O4 tetrahedra, corners with two equivalent Ni(5)O4 tetrahedra, corners with two equivalent Ni(9)O4 tetrahedra,  an edgeedge with one Ca(4)O6 octahedra,  an edgeedge with one Ni(3)O6 octahedra, and edges with four equivalent Ni(6)O6 octahedra. The Ca(6)-O(13) bond length is 2.26 Å. The Ca(6)-O(18) bond length is 2.25 Å. Both Ca(6)-O(10) bond lengths are 2.26 Å. Both Ca(6)-O(17) bond lengths are 2.27 Å. There are nine inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(7), and one O(8) atom to form NiO6 octahedra that share  a cornercorner with one Ni(2)O4 tetrahedra,  a cornercorner with one Ni(9)O4 tetrahedra, corners with two equivalent Ca(1)O4 tetrahedra, corners with two equivalent Ni(7)O4 tetrahedra,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Ni(3)O6 octahedra, edges with two equivalent Ca(3)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. The Ni(1)-O(1) bond length is 1.86 Å. The Ni(1)-O(2) bond length is 2.17 Å. The Ni(1)-O(3) bond length is 2.00 Å. The Ni(1)-O(5) bond length is 2.13 Å. The Ni(1)-O(7) bond length is 1.89 Å. The Ni(1)-O(8) bond length is 2.07 Å. In the second Ni site, Ni(2) is bonded to one O(2), one O(9), and two equivalent O(4) atoms to form NiO4 tetrahedra that share  a cornercorner with one Ca(3)O6 octahedra, corners with two equivalent Ca(5)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, corners with three equivalent Ca(2)O6 octahedra, and corners with four equivalent Ni(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-61°. The Ni(2)-O(2) bond length is 1.90 Å. The Ni(2)-O(9) bond length is 1.96 Å. Both Ni(2)-O(4) bond lengths are 1.87 Å. In the third Ni site, Ni(3) is bonded to one O(16), one O(3), two equivalent O(1), and two equivalent O(17) atoms to form NiO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Ni(9)O4 tetrahedra,  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(6)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(6)O6 octahedra. The Ni(3)-O(16) bond length is 1.92 Å. The Ni(3)-O(3) bond length is 1.93 Å. Both Ni(3)-O(1) bond lengths are 1.86 Å. Both Ni(3)-O(17) bond lengths are 1.94 Å. In the fourth Ni site, Ni(4) is bonded to one O(11), one O(12), one O(14), one O(4), one O(6), and one O(9) atom to form NiO6 octahedra that share  a cornercorner with one Ni(5)O4 tetrahedra,  a cornercorner with one Ni(7)O4 tetrahedra, corners with two equivalent Ni(2)O4 tetrahedra, corners with two equivalent Ni(8)O4 tetrahedra,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Ca(4)O6 octahedra, edges with two equivalent Ca(5)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. The Ni(4)-O(11) bond length is 2.11 Å. The Ni(4)-O(12) bond length is 1.91 Å. The Ni(4)-O(14) bond length is 2.08 Å. The Ni(4)-O(4) bond length is 1.94 Å. The Ni(4)-O(6) bond length is 2.10 Å. The Ni(4)-O(9) bond length is 2.16 Å. In the fifth Ni site, Ni(5) is bonded to one O(15), one O(6), and two equivalent O(10) atoms to form NiO4 tetrahedra that share  a cornercorner with one Ca(5)O6 octahedra, corners with two equivalent Ca(6)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra, corners with three equivalent Ca(4)O6 octahedra, and corners with four equivalent Ni(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-64°. The Ni(5)-O(15) bond length is 1.85 Å. The Ni(5)-O(6) bond length is 1.92 Å. Both Ni(5)-O(10) bond lengths are 1.87 Å. In the sixth Ni site, Ni(6) is bonded to one O(10), one O(13), one O(15), one O(16), one O(17), and one O(18) atom to form NiO6 octahedra that share  a cornercorner with one Ca(1)O4 tetrahedra,  a cornercorner with one Ni(8)O4 tetrahedra, corners with two equivalent Ni(5)O4 tetrahedra, corners with two equivalent Ni(9)O4 tetrahedra,  an edgeedge with one Ca(4)O6 octahedra,  an edgeedge with one Ni(3)O6 octahedra, edges with two equivalent Ca(6)O6 octahedra, and edges with two equivalent Ni(6)O6 octahedra. The Ni(6)-O(10) bond length is 1.92 Å. The Ni(6)-O(13) bond length is 1.93 Å. The Ni(6)-O(15) bond length is 2.32 Å. The Ni(6)-O(16) bond length is 2.20 Å. The Ni(6)-O(17) bond length is 1.97 Å. The Ni(6)-O(18) bond length is 1.97 Å. In the seventh Ni site, Ni(7) is bonded to one O(14), one O(5), and two equivalent O(7) atoms to form NiO4 tetrahedra that share  a cornercorner with one Ca(5)O6 octahedra, corners with two equivalent Ca(3)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra, corners with three equivalent Ca(2)O6 octahedra, and corners with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-67°. The Ni(7)-O(14) bond length is 1.96 Å. The Ni(7)-O(5) bond length is 2.07 Å. Both Ni(7)-O(7) bond lengths are 1.91 Å. In the eighth Ni site, Ni(8) is bonded to one O(11), one O(18), and two equivalent O(12) atoms to form NiO4 tetrahedra that share  a cornercorner with one Ca(6)O6 octahedra, corners with two equivalent Ca(5)O6 octahedra, corners with two equivalent Ni(6)O6 octahedra, corners with three equivalent Ca(4)O6 octahedra, and corners with four equivalent Ni(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-69°. The Ni(8)-O(11) bond length is 2.02 Å. The Ni(8)-O(18) bond length is 2.09 Å. Both Ni(8)-O(12) bond lengths are 1.91 Å. In the ninth Ni site, Ni(9) is bonded to one O(16), one O(8), and two equivalent O(17) atoms to form NiO4 tetrahedra that share  a cornercorner with one Ca(3)O6 octahedra, corners with two equivalent Ca(6)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, corners with three equivalent Ni(3)O6 octahedra, and corners with four equivalent Ni(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-66°. The Ni(9)-O(16) bond length is 2.19 Å. The Ni(9)-O(8) bond length is 1.95 Å. Both Ni(9)-O(17) bond lengths are 2.00 Å. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ca(3), one Ni(1), and one Ni(3) atom to form distorted OCa2Ni2 tetrahedra that share  a cornercorner with one O(1)Ca2Ni2 tetrahedra,  a cornercorner with one O(13)Ca2Ni2 tetrahedra,  a cornercorner with one O(3)CaNi3 trigonal pyramid, corners with two equivalent O(8)CaNi3 trigonal pyramids,  an edgeedge with one O(1)Ca2Ni2 tetrahedra, and  an edgeedge with one O(3)CaNi3 trigonal pyramid. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Ca(3), one Ni(2), and two equivalent Ni(1) atoms. In the third O site, O(3) is bonded to one Ca(1), one Ni(3), and two equivalent Ni(1) atoms to form distorted OCaNi3 trigonal pyramids that share  a cornercorner with one O(13)Ca2Ni2 tetrahedra, corners with two equivalent O(1)Ca2Ni2 tetrahedra, corners with two equivalent O(8)CaNi3 trigonal pyramids, and edges with two equivalent O(1)Ca2Ni2 tetrahedra. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Ca(2), one Ca(5), one Ni(2), and one Ni(4) atom. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Ca(2), one Ni(7), and two equivalent Ni(1) atoms. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Ca(5), one Ni(5), and two equivalent Ni(4) atoms. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to one Ca(2), one Ca(3), one Ni(1), and one Ni(7) atom. In the eighth O site, O(8) is bonded to one Ca(3), one Ni(9), and two equivalent Ni(1) atoms to form distorted OCaNi3 trigonal pyramids that share corners with four equivalent O(1)Ca2Ni2 tetrahedra and corners with two equivalent O(3)CaNi3 trigonal pyramids. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to one Ca(2), one Ni(2), and two equivalent Ni(4) atoms. In the tenth O site, O(10) is bonded in a rectangular see-saw-like geometry to one Ca(4), one Ca(6), one Ni(5), and one Ni(6) atom. In the eleventh O site, O(11) is bonded in a rectangular see-saw-like geometry to one Ca(4), one Ni(8), and two equivalent Ni(4) atoms. In the twelfth O site, O(12) is bonded in a rectangular see-saw-like geometry to one Ca(4), one Ca(5), one Ni(4), and one Ni(8) atom. In the thirteenth O site, O(13) is bonded to one Ca(1), one Ca(6), and two equivalent Ni(6) atoms to form distorted OCa2Ni2 tetrahedra that share corners with two equivalent O(1)Ca2Ni2 tetrahedra and  a cornercorner with one O(3)CaNi3 trigonal pyramid. In the fourteenth O site, O(14) is bonded in a rectangular see-saw-like geometry to one Ca(5), one Ni(7), and two equivalent Ni(4) atoms. In the fifteenth O site, O(15) is bonded in a distorted rectangular see-saw-like geometry to one Ca(4), one Ni(5), and two equivalent Ni(6) atoms. In the sixteenth O site, O(16) is bonded in a rectangular see-saw-like geometry to one Ni(3), one Ni(9), and two equivalent Ni(6) atoms. In the seventeenth O site, O(17) is bonded in a rectangular see-saw-like geometry to one Ca(6), one Ni(3), one Ni(6), and one Ni(9) atom. In the eighteenth O site, O(18) is bonded in a rectangular see-saw-like geometry to one Ca(6), one Ni(8), and two equivalent Ni(6) atoms.