CaMn2O4 is Spinel-like structured and crystallizes in the trigonal R3m space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(3) and three equivalent O(4) atoms to form CaO4 tetrahedra that share corners with three equivalent Ca(2)O6 octahedra and corners with nine equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-69°. In the second Ca site, Ca(2) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form distorted CaO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Mn(1)O4 tetrahedra, and edges with six equivalent Mn(2)O6 octahedra. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(2) and three equivalent O(1) atoms to form MnO4 tetrahedra that share corners with three equivalent Ca(2)O6 octahedra and corners with nine equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-67°. In the second Mn site, Mn(2) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Mn(1)O4 tetrahedra, edges with two equivalent Ca(2)O6 octahedra, and edges with four equivalent Mn(2)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ca(2), one Mn(1), and two equivalent Mn(2) atoms to form distorted OCaMn3 trigonal pyramids that share corners with seven equivalent O(4)Ca2Mn2 tetrahedra, corners with two equivalent O(1)CaMn3 trigonal pyramids, and edges with two equivalent O(1)CaMn3 trigonal pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Mn(1) and three equivalent Mn(2) atoms. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Ca(1) and three equivalent Mn(2) atoms. In the fourth O site, O(4) is bonded to one Ca(1), one Ca(2), and two equivalent Mn(2) atoms to form distorted OCa2Mn2 tetrahedra that share corners with two equivalent O(4)Ca2Mn2 tetrahedra, corners with seven equivalent O(1)CaMn3 trigonal pyramids, and edges with two equivalent O(4)Ca2Mn2 tetrahedra.
CaMn2O4 is Spinel-like structured and crystallizes in the trigonal R3m space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(3) and three equivalent O(4) atoms to form CaO4 tetrahedra that share corners with three equivalent Ca(2)O6 octahedra and corners with nine equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-69°. The Ca(1)-O(3) bond length is 2.27 Å. All Ca(1)-O(4) bond lengths are 2.19 Å. In the second Ca site, Ca(2) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form distorted CaO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Mn(1)O4 tetrahedra, and edges with six equivalent Mn(2)O6 octahedra. All Ca(2)-O(1) bond lengths are 2.31 Å. All Ca(2)-O(4) bond lengths are 2.29 Å. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(2) and three equivalent O(1) atoms to form MnO4 tetrahedra that share corners with three equivalent Ca(2)O6 octahedra and corners with nine equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-67°. The Mn(1)-O(2) bond length is 2.13 Å. All Mn(1)-O(1) bond lengths are 2.12 Å. In the second Mn site, Mn(2) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Mn(1)O4 tetrahedra, edges with two equivalent Ca(2)O6 octahedra, and edges with four equivalent Mn(2)O6 octahedra. The Mn(2)-O(2) bond length is 2.25 Å. The Mn(2)-O(3) bond length is 2.14 Å. Both Mn(2)-O(1) bond lengths are 2.01 Å. Both Mn(2)-O(4) bond lengths are 1.96 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ca(2), one Mn(1), and two equivalent Mn(2) atoms to form distorted OCaMn3 trigonal pyramids that share corners with seven equivalent O(4)Ca2Mn2 tetrahedra, corners with two equivalent O(1)CaMn3 trigonal pyramids, and edges with two equivalent O(1)CaMn3 trigonal pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Mn(1) and three equivalent Mn(2) atoms. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Ca(1) and three equivalent Mn(2) atoms. In the fourth O site, O(4) is bonded to one Ca(1), one Ca(2), and two equivalent Mn(2) atoms to form distorted OCa2Mn2 tetrahedra that share corners with two equivalent O(4)Ca2Mn2 tetrahedra, corners with seven equivalent O(1)CaMn3 trigonal pyramids, and edges with two equivalent O(4)Ca2Mn2 tetrahedra.