CaCr2O4 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 Cr(6)O6 octahedra, corners with three equivalent Cr(3)O6 octahedra, and corners with four equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-71°. 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 Cr(2)O4 tetrahedra, corners with three equivalent Cr(7)O4 tetrahedra,  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(5)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, and edges with two equivalent Cr(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 Cr(2)O4 tetrahedra,  a cornercorner with one Cr(9)O4 tetrahedra, corners with two equivalent Ca(1)O4 tetrahedra, corners with two equivalent Cr(7)O4 tetrahedra,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Cr(3)O6 octahedra, and edges with four equivalent Cr(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 Cr(5)O4 tetrahedra, corners with three equivalent Cr(8)O4 tetrahedra,  an edgeedge with one Ca(5)O6 octahedra,  an edgeedge with one Ca(6)O6 octahedra, edges with two equivalent Cr(4)O6 octahedra, and edges with two equivalent Cr(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 Cr(5)O4 tetrahedra,  a cornercorner with one Cr(7)O4 tetrahedra, corners with two equivalent Cr(2)O4 tetrahedra, corners with two equivalent Cr(8)O4 tetrahedra,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Ca(4)O6 octahedra, and edges with four equivalent Cr(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 Cr(8)O4 tetrahedra, corners with two equivalent Cr(5)O4 tetrahedra, corners with two equivalent Cr(9)O4 tetrahedra,  an edgeedge with one Ca(4)O6 octahedra,  an edgeedge with one Cr(3)O6 octahedra, and edges with four equivalent Cr(6)O6 octahedra. There are nine inequivalent Cr sites. In the first Cr site, Cr(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 CrO6 octahedra that share  a cornercorner with one Cr(2)O4 tetrahedra,  a cornercorner with one Cr(9)O4 tetrahedra, corners with two equivalent Ca(1)O4 tetrahedra, corners with two equivalent Cr(7)O4 tetrahedra,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Cr(3)O6 octahedra, edges with two equivalent Ca(3)O6 octahedra, and edges with two equivalent Cr(1)O6 octahedra. In the second Cr site, Cr(2) is bonded to one O(2), one O(9), and two equivalent O(4) atoms to form CrO4 tetrahedra that share  a cornercorner with one Ca(3)O6 octahedra, corners with two equivalent Ca(5)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, corners with three equivalent Ca(2)O6 octahedra, and corners with four equivalent Cr(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-64°. In the third Cr site, Cr(3) is bonded to one O(16), one O(3), two equivalent O(1), and two equivalent O(17) atoms to form CrO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Cr(9)O4 tetrahedra,  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(6)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, and edges with two equivalent Cr(6)O6 octahedra. In the fourth Cr site, Cr(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 CrO6 octahedra that share  a cornercorner with one Cr(5)O4 tetrahedra,  a cornercorner with one Cr(7)O4 tetrahedra, corners with two equivalent Cr(2)O4 tetrahedra, corners with two equivalent Cr(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 Cr(4)O6 octahedra. In the fifth Cr site, Cr(5) is bonded to one O(15), one O(6), and two equivalent O(10) atoms to form CrO4 tetrahedra that share  a cornercorner with one Ca(5)O6 octahedra, corners with two equivalent Ca(6)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, corners with three equivalent Ca(4)O6 octahedra, and corners with four equivalent Cr(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-66°. In the sixth Cr site, Cr(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 CrO6 octahedra that share  a cornercorner with one Ca(1)O4 tetrahedra,  a cornercorner with one Cr(8)O4 tetrahedra, corners with two equivalent Cr(5)O4 tetrahedra, corners with two equivalent Cr(9)O4 tetrahedra,  an edgeedge with one Ca(4)O6 octahedra,  an edgeedge with one Cr(3)O6 octahedra, edges with two equivalent Ca(6)O6 octahedra, and edges with two equivalent Cr(6)O6 octahedra. In the seventh Cr site, Cr(7) is bonded to one O(14), one O(5), and two equivalent O(7) atoms to form CrO4 tetrahedra that share  a cornercorner with one Ca(5)O6 octahedra, corners with two equivalent Ca(3)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, corners with three equivalent Ca(2)O6 octahedra, and corners with four equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-65°. In the eighth Cr site, Cr(8) is bonded to one O(11), one O(18), and two equivalent O(12) atoms to form CrO4 tetrahedra that share  a cornercorner with one Ca(6)O6 octahedra, corners with two equivalent Ca(5)O6 octahedra, corners with two equivalent Cr(6)O6 octahedra, corners with three equivalent Ca(4)O6 octahedra, and corners with four equivalent Cr(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-64°. In the ninth Cr site, Cr(9) is bonded to one O(16), one O(8), and two equivalent O(17) atoms to form CrO4 tetrahedra that share  a cornercorner with one Ca(3)O6 octahedra, corners with two equivalent Ca(6)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, corners with three equivalent Cr(3)O6 octahedra, and corners with four equivalent Cr(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-61°. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ca(3), one Cr(1), and one Cr(3) atom to form distorted OCa2Cr2 trigonal pyramids that share  a cornercorner with one O(13)Ca2Cr2 tetrahedra,  a cornercorner with one O(1)Ca2Cr2 trigonal pyramid,  a cornercorner with one O(3)CaCr3 trigonal pyramid,  a cornercorner with one O(16)Cr4 trigonal pyramid,  an edgeedge with one O(1)Ca2Cr2 trigonal pyramid, and  an edgeedge with one O(3)CaCr3 trigonal pyramid. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Ca(3), one Cr(2), and two equivalent Cr(1) atoms. In the third O site, O(3) is bonded to one Ca(1), one Cr(3), and two equivalent Cr(1) atoms to form distorted OCaCr3 trigonal pyramids that share  a cornercorner with one O(13)Ca2Cr2 tetrahedra,  a cornercorner with one O(16)Cr4 trigonal pyramid, corners with two equivalent O(1)Ca2Cr2 trigonal pyramids, and edges with two equivalent O(1)Ca2Cr2 trigonal pyramids. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Ca(2), one Ca(5), one Cr(2), and one Cr(4) atom. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Ca(2), one Cr(7), and two equivalent Cr(1) atoms. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Ca(5), one Cr(5), and two equivalent Cr(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 Cr(1), and one Cr(7) atom. In the eighth O site, O(8) is bonded in a rectangular see-saw-like geometry to one Ca(3), one Cr(9), and two equivalent Cr(1) atoms. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to one Ca(2), one Cr(2), and two equivalent Cr(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 Cr(5), and one Cr(6) atom. In the eleventh O site, O(11) is bonded in a rectangular see-saw-like geometry to one Ca(4), one Cr(8), and two equivalent Cr(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 Cr(4), and one Cr(8) atom. In the thirteenth O site, O(13) is bonded to one Ca(1), one Ca(6), and two equivalent Cr(6) atoms to form OCa2Cr2 tetrahedra that share  a cornercorner with one O(3)CaCr3 trigonal pyramid, corners with two equivalent O(1)Ca2Cr2 trigonal pyramids, and corners with two equivalent O(16)Cr4 trigonal pyramids. In the fourteenth O site, O(14) is bonded in a rectangular see-saw-like geometry to one Ca(5), one Cr(7), and two equivalent Cr(4) atoms. In the fifteenth O site, O(15) is bonded in a rectangular see-saw-like geometry to one Ca(4), one Cr(5), and two equivalent Cr(6) atoms. In the sixteenth O site, O(16) is bonded to one Cr(3), one Cr(9), and two equivalent Cr(6) atoms to form distorted OCr4 trigonal pyramids that share corners with two equivalent O(13)Ca2Cr2 tetrahedra,  a cornercorner with one O(3)CaCr3 trigonal pyramid, and corners with two equivalent O(1)Ca2Cr2 trigonal pyramids. In the seventeenth O site, O(17) is bonded in a rectangular see-saw-like geometry to one Ca(6), one Cr(3), one Cr(6), and one Cr(9) atom. In the eighteenth O site, O(18) is bonded in a rectangular see-saw-like geometry to one Ca(6), one Cr(8), and two equivalent Cr(6) atoms.
CaCr2O4 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 Cr(6)O6 octahedra, corners with three equivalent Cr(3)O6 octahedra, and corners with four equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-71°. The Ca(1)-O(13) bond length is 2.23 Å. The Ca(1)-O(3) bond length is 2.28 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 Cr(2)O4 tetrahedra, corners with three equivalent Cr(7)O4 tetrahedra,  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(5)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, and edges with two equivalent Cr(4)O6 octahedra. The Ca(2)-O(5) bond length is 2.33 Å. The Ca(2)-O(9) bond length is 2.31 Å. Both Ca(2)-O(4) bond lengths are 2.28 Å. Both Ca(2)-O(7) bond lengths are 2.29 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 Cr(2)O4 tetrahedra,  a cornercorner with one Cr(9)O4 tetrahedra, corners with two equivalent Ca(1)O4 tetrahedra, corners with two equivalent Cr(7)O4 tetrahedra,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Cr(3)O6 octahedra, and edges with four equivalent Cr(1)O6 octahedra. The Ca(3)-O(2) bond length is 2.32 Å. The Ca(3)-O(8) bond length is 2.32 Å. Both Ca(3)-O(1) bond lengths are 2.22 Å. Both Ca(3)-O(7) bond lengths are 2.26 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 Cr(5)O4 tetrahedra, corners with three equivalent Cr(8)O4 tetrahedra,  an edgeedge with one Ca(5)O6 octahedra,  an edgeedge with one Ca(6)O6 octahedra, edges with two equivalent Cr(4)O6 octahedra, and edges with two equivalent Cr(6)O6 octahedra. The Ca(4)-O(11) bond length is 2.30 Å. The Ca(4)-O(15) bond length is 2.32 Å. Both Ca(4)-O(10) bond lengths are 2.28 Å. Both Ca(4)-O(12) bond lengths are 2.27 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 Cr(5)O4 tetrahedra,  a cornercorner with one Cr(7)O4 tetrahedra, corners with two equivalent Cr(2)O4 tetrahedra, corners with two equivalent Cr(8)O4 tetrahedra,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Ca(4)O6 octahedra, and edges with four equivalent Cr(4)O6 octahedra. The Ca(5)-O(14) bond length is 2.31 Å. The Ca(5)-O(6) bond length is 2.31 Å. Both Ca(5)-O(12) bond lengths are 2.28 Å. Both Ca(5)-O(4) bond lengths are 2.28 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 Cr(8)O4 tetrahedra, corners with two equivalent Cr(5)O4 tetrahedra, corners with two equivalent Cr(9)O4 tetrahedra,  an edgeedge with one Ca(4)O6 octahedra,  an edgeedge with one Cr(3)O6 octahedra, and edges with four equivalent Cr(6)O6 octahedra. The Ca(6)-O(13) bond length is 2.23 Å. The Ca(6)-O(18) bond length is 2.29 Å. Both Ca(6)-O(10) bond lengths are 2.30 Å. Both Ca(6)-O(17) bond lengths are 2.32 Å. There are nine inequivalent Cr sites. In the first Cr site, Cr(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 CrO6 octahedra that share  a cornercorner with one Cr(2)O4 tetrahedra,  a cornercorner with one Cr(9)O4 tetrahedra, corners with two equivalent Ca(1)O4 tetrahedra, corners with two equivalent Cr(7)O4 tetrahedra,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Cr(3)O6 octahedra, edges with two equivalent Ca(3)O6 octahedra, and edges with two equivalent Cr(1)O6 octahedra. The Cr(1)-O(1) bond length is 1.96 Å. The Cr(1)-O(2) bond length is 2.10 Å. The Cr(1)-O(3) bond length is 2.02 Å. The Cr(1)-O(5) bond length is 2.12 Å. The Cr(1)-O(7) bond length is 2.08 Å. The Cr(1)-O(8) bond length is 2.14 Å. In the second Cr site, Cr(2) is bonded to one O(2), one O(9), and two equivalent O(4) atoms to form CrO4 tetrahedra that share  a cornercorner with one Ca(3)O6 octahedra, corners with two equivalent Ca(5)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, corners with three equivalent Ca(2)O6 octahedra, and corners with four equivalent Cr(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-64°. The Cr(2)-O(2) bond length is 2.00 Å. The Cr(2)-O(9) bond length is 2.11 Å. Both Cr(2)-O(4) bond lengths are 1.89 Å. In the third Cr site, Cr(3) is bonded to one O(16), one O(3), two equivalent O(1), and two equivalent O(17) atoms to form CrO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Cr(9)O4 tetrahedra,  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(6)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, and edges with two equivalent Cr(6)O6 octahedra. The Cr(3)-O(16) bond length is 2.08 Å. The Cr(3)-O(3) bond length is 2.01 Å. Both Cr(3)-O(1) bond lengths are 1.95 Å. Both Cr(3)-O(17) bond lengths are 2.09 Å. In the fourth Cr site, Cr(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 CrO6 octahedra that share  a cornercorner with one Cr(5)O4 tetrahedra,  a cornercorner with one Cr(7)O4 tetrahedra, corners with two equivalent Cr(2)O4 tetrahedra, corners with two equivalent Cr(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 Cr(4)O6 octahedra. The Cr(4)-O(11) bond length is 2.09 Å. The Cr(4)-O(12) bond length is 2.06 Å. The Cr(4)-O(14) bond length is 2.09 Å. The Cr(4)-O(4) bond length is 2.05 Å. The Cr(4)-O(6) bond length is 2.10 Å. The Cr(4)-O(9) bond length is 2.11 Å. In the fifth Cr site, Cr(5) is bonded to one O(15), one O(6), and two equivalent O(10) atoms to form CrO4 tetrahedra that share  a cornercorner with one Ca(5)O6 octahedra, corners with two equivalent Ca(6)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, corners with three equivalent Ca(4)O6 octahedra, and corners with four equivalent Cr(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-66°. The Cr(5)-O(15) bond length is 2.05 Å. The Cr(5)-O(6) bond length is 2.02 Å. Both Cr(5)-O(10) bond lengths are 1.89 Å. In the sixth Cr site, Cr(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 CrO6 octahedra that share  a cornercorner with one Ca(1)O4 tetrahedra,  a cornercorner with one Cr(8)O4 tetrahedra, corners with two equivalent Cr(5)O4 tetrahedra, corners with two equivalent Cr(9)O4 tetrahedra,  an edgeedge with one Ca(4)O6 octahedra,  an edgeedge with one Cr(3)O6 octahedra, edges with two equivalent Ca(6)O6 octahedra, and edges with two equivalent Cr(6)O6 octahedra. The Cr(6)-O(10) bond length is 2.05 Å. The Cr(6)-O(13) bond length is 2.00 Å. The Cr(6)-O(15) bond length is 2.14 Å. The Cr(6)-O(16) bond length is 2.09 Å. The Cr(6)-O(17) bond length is 2.07 Å. The Cr(6)-O(18) bond length is 2.10 Å. In the seventh Cr site, Cr(7) is bonded to one O(14), one O(5), and two equivalent O(7) atoms to form CrO4 tetrahedra that share  a cornercorner with one Ca(5)O6 octahedra, corners with two equivalent Ca(3)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, corners with three equivalent Ca(2)O6 octahedra, and corners with four equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-65°. The Cr(7)-O(14) bond length is 2.02 Å. The Cr(7)-O(5) bond length is 2.10 Å. Both Cr(7)-O(7) bond lengths are 1.89 Å. In the eighth Cr site, Cr(8) is bonded to one O(11), one O(18), and two equivalent O(12) atoms to form CrO4 tetrahedra that share  a cornercorner with one Ca(6)O6 octahedra, corners with two equivalent Ca(5)O6 octahedra, corners with two equivalent Cr(6)O6 octahedra, corners with three equivalent Ca(4)O6 octahedra, and corners with four equivalent Cr(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-64°. The Cr(8)-O(11) bond length is 2.11 Å. The Cr(8)-O(18) bond length is 2.01 Å. Both Cr(8)-O(12) bond lengths are 1.89 Å. In the ninth Cr site, Cr(9) is bonded to one O(16), one O(8), and two equivalent O(17) atoms to form CrO4 tetrahedra that share  a cornercorner with one Ca(3)O6 octahedra, corners with two equivalent Ca(6)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, corners with three equivalent Cr(3)O6 octahedra, and corners with four equivalent Cr(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-61°. The Cr(9)-O(16) bond length is 2.38 Å. The Cr(9)-O(8) bond length is 1.93 Å. Both Cr(9)-O(17) bond lengths are 1.91 Å. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ca(3), one Cr(1), and one Cr(3) atom to form distorted OCa2Cr2 trigonal pyramids that share  a cornercorner with one O(13)Ca2Cr2 tetrahedra,  a cornercorner with one O(1)Ca2Cr2 trigonal pyramid,  a cornercorner with one O(3)CaCr3 trigonal pyramid,  a cornercorner with one O(16)Cr4 trigonal pyramid,  an edgeedge with one O(1)Ca2Cr2 trigonal pyramid, and  an edgeedge with one O(3)CaCr3 trigonal pyramid. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Ca(3), one Cr(2), and two equivalent Cr(1) atoms. In the third O site, O(3) is bonded to one Ca(1), one Cr(3), and two equivalent Cr(1) atoms to form distorted OCaCr3 trigonal pyramids that share  a cornercorner with one O(13)Ca2Cr2 tetrahedra,  a cornercorner with one O(16)Cr4 trigonal pyramid, corners with two equivalent O(1)Ca2Cr2 trigonal pyramids, and edges with two equivalent O(1)Ca2Cr2 trigonal pyramids. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Ca(2), one Ca(5), one Cr(2), and one Cr(4) atom. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Ca(2), one Cr(7), and two equivalent Cr(1) atoms. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Ca(5), one Cr(5), and two equivalent Cr(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 Cr(1), and one Cr(7) atom. In the eighth O site, O(8) is bonded in a rectangular see-saw-like geometry to one Ca(3), one Cr(9), and two equivalent Cr(1) atoms. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to one Ca(2), one Cr(2), and two equivalent Cr(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 Cr(5), and one Cr(6) atom. In the eleventh O site, O(11) is bonded in a rectangular see-saw-like geometry to one Ca(4), one Cr(8), and two equivalent Cr(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 Cr(4), and one Cr(8) atom. In the thirteenth O site, O(13) is bonded to one Ca(1), one Ca(6), and two equivalent Cr(6) atoms to form OCa2Cr2 tetrahedra that share  a cornercorner with one O(3)CaCr3 trigonal pyramid, corners with two equivalent O(1)Ca2Cr2 trigonal pyramids, and corners with two equivalent O(16)Cr4 trigonal pyramids. In the fourteenth O site, O(14) is bonded in a rectangular see-saw-like geometry to one Ca(5), one Cr(7), and two equivalent Cr(4) atoms. In the fifteenth O site, O(15) is bonded in a rectangular see-saw-like geometry to one Ca(4), one Cr(5), and two equivalent Cr(6) atoms. In the sixteenth O site, O(16) is bonded to one Cr(3), one Cr(9), and two equivalent Cr(6) atoms to form distorted OCr4 trigonal pyramids that share corners with two equivalent O(13)Ca2Cr2 tetrahedra,  a cornercorner with one O(3)CaCr3 trigonal pyramid, and corners with two equivalent O(1)Ca2Cr2 trigonal pyramids. In the seventeenth O site, O(17) is bonded in a rectangular see-saw-like geometry to one Ca(6), one Cr(3), one Cr(6), and one Cr(9) atom. In the eighteenth O site, O(18) is bonded in a rectangular see-saw-like geometry to one Ca(6), one Cr(8), and two equivalent Cr(6) atoms.