CaMn2O4 crystallizes in the monoclinic C2 space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent O(1), two equivalent O(7), and two equivalent O(8) atoms to form distorted CaO6 octahedra that share corners with four equivalent Ca(3)O6 octahedra, corners with two equivalent Mn(2)O5 square pyramids, corners with four equivalent Mn(4)O5 square pyramids, edges with two equivalent Mn(1)O5 square pyramids, and edges with two equivalent Mn(4)O5 square pyramids. The corner-sharing octahedral tilt angles range from 46-48°. In the second Ca site, Ca(2) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms to form CaO6 octahedra that share corners with four equivalent Ca(3)O6 octahedra, corners with two equivalent Mn(1)O5 square pyramids, corners with four equivalent Mn(3)O5 square pyramids, edges with two equivalent Mn(2)O5 square pyramids, and edges with two equivalent Mn(3)O5 square pyramids. The corner-sharing octahedral tilt angles range from 47-49°. In the third Ca site, Ca(3) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(8) atom to form CaO6 octahedra that share corners with two equivalent Ca(1)O6 octahedra, corners with two equivalent Ca(2)O6 octahedra,  a cornercorner with one Mn(3)O5 square pyramid,  a cornercorner with one Mn(4)O5 square pyramid, corners with two equivalent Mn(1)O5 square pyramids, corners with two equivalent Mn(2)O5 square pyramids,  an edgeedge with one Mn(1)O5 square pyramid,  an edgeedge with one Mn(2)O5 square pyramid,  an edgeedge with one Mn(3)O5 square pyramid, and  an edgeedge with one Mn(4)O5 square pyramid. The corner-sharing octahedral tilt angles range from 46-49°. There are four inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(7) atom to form distorted MnO5 square pyramids that share  a cornercorner with one Ca(2)O6 octahedra, corners with two equivalent Ca(3)O6 octahedra,  a cornercorner with one Mn(3)O5 square pyramid, corners with three equivalent Mn(4)O5 square pyramids,  an edgeedge with one Ca(1)O6 octahedra,  an edgeedge with one Ca(3)O6 octahedra, and edges with two equivalent Mn(2)O5 square pyramids. The corner-sharing octahedral tilt angles range from 59-71°. In the second Mn site, Mn(2) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(6) atom to form distorted MnO5 square pyramids that share  a cornercorner with one Ca(1)O6 octahedra, corners with two equivalent Ca(3)O6 octahedra,  a cornercorner with one Mn(4)O5 square pyramid, corners with three equivalent Mn(3)O5 square pyramids,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Ca(3)O6 octahedra, and edges with two equivalent Mn(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 59-76°. In the third Mn site, Mn(3) is bonded to one O(4), two equivalent O(5), and two equivalent O(6) atoms to form distorted MnO5 square pyramids that share  a cornercorner with one Ca(3)O6 octahedra, corners with two equivalent Ca(2)O6 octahedra,  a cornercorner with one Mn(1)O5 square pyramid, corners with three equivalent Mn(2)O5 square pyramids,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Ca(3)O6 octahedra, and edges with two equivalent Mn(3)O5 square pyramids. The corner-sharing octahedral tilt angles range from 57-71°. In the fourth Mn site, Mn(4) is bonded to one O(2), two equivalent O(7), and two equivalent O(8) atoms to form distorted MnO5 square pyramids that share  a cornercorner with one Ca(3)O6 octahedra, corners with two equivalent Ca(1)O6 octahedra,  a cornercorner with one Mn(2)O5 square pyramid, corners with three equivalent Mn(1)O5 square pyramids,  an edgeedge with one Ca(1)O6 octahedra,  an edgeedge with one Ca(3)O6 octahedra, and edges with two equivalent Mn(4)O5 square pyramids. The corner-sharing octahedral tilt angles range from 56-69°. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ca(3), one Mn(1), and one Mn(2) atom to form OCa2Mn2 trigonal pyramids that share  a cornercorner with one O(1)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(3)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(5)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  a cornercorner with one O(6)CaMn3 trigonal pyramid,  a cornercorner with one O(7)CaMn3 trigonal pyramid, corners with three equivalent O(8)Ca2Mn2 trigonal pyramids, corners with three equivalent O(4)CaMn3 trigonal pyramids,  an edgeedge with one O(3)Ca2Mn2 trigonal pyramid,  an edgeedge with one O(2)CaMn3 trigonal pyramid, and  an edgeedge with one O(7)CaMn3 trigonal pyramid. In the second O site, O(2) is bonded to one Ca(3), one Mn(1), one Mn(2), and one Mn(4) atom to form distorted OCaMn3 trigonal pyramids that share  a cornercorner with one O(1)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(5)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(8)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(4)CaMn3 trigonal pyramid,  a cornercorner with one O(6)CaMn3 trigonal pyramid, corners with three equivalent O(3)Ca2Mn2 trigonal pyramids, corners with three equivalent O(7)CaMn3 trigonal pyramids,  an edgeedge with one O(1)Ca2Mn2 trigonal pyramid,  an edgeedge with one O(8)Ca2Mn2 trigonal pyramid, and  an edgeedge with one O(4)CaMn3 trigonal pyramid. In the third O site, O(3) is bonded to one Ca(2), one Ca(3), one Mn(1), and one Mn(2) atom to form OCa2Mn2 trigonal pyramids that share  a cornercorner with one O(1)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(3)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(8)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(4)CaMn3 trigonal pyramid,  a cornercorner with one O(6)CaMn3 trigonal pyramid,  a cornercorner with one O(7)CaMn3 trigonal pyramid, corners with three equivalent O(5)Ca2Mn2 trigonal pyramids, corners with three equivalent O(2)CaMn3 trigonal pyramids,  an edgeedge with one O(1)Ca2Mn2 trigonal pyramid,  an edgeedge with one O(4)CaMn3 trigonal pyramid, and  an edgeedge with one O(6)CaMn3 trigonal pyramid. In the fourth O site, O(4) is bonded to one Ca(3), one Mn(1), one Mn(2), and one Mn(3) atom to form distorted OCaMn3 trigonal pyramids that share  a cornercorner with one O(3)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(5)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(8)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  a cornercorner with one O(7)CaMn3 trigonal pyramid, corners with three equivalent O(1)Ca2Mn2 trigonal pyramids, corners with three equivalent O(6)CaMn3 trigonal pyramids,  an edgeedge with one O(3)Ca2Mn2 trigonal pyramid,  an edgeedge with one O(5)Ca2Mn2 trigonal pyramid, and  an edgeedge with one O(2)CaMn3 trigonal pyramid. In the fifth O site, O(5) is bonded to one Ca(2), one Ca(3), and two equivalent Mn(3) atoms to form OCa2Mn2 trigonal pyramids that share  a cornercorner with one O(1)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(8)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  a cornercorner with one O(4)CaMn3 trigonal pyramid, corners with two equivalent O(6)CaMn3 trigonal pyramids, corners with three equivalent O(3)Ca2Mn2 trigonal pyramids, corners with three equivalent O(5)Ca2Mn2 trigonal pyramids,  an edgeedge with one O(4)CaMn3 trigonal pyramid, and edges with two equivalent O(6)CaMn3 trigonal pyramids. In the sixth O site, O(6) is bonded to one Ca(2), one Mn(2), and two equivalent Mn(3) atoms to form distorted OCaMn3 trigonal pyramids that share  a cornercorner with one O(1)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(3)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(2)CaMn3 trigonal pyramid, corners with two equivalent O(5)Ca2Mn2 trigonal pyramids, corners with three equivalent O(4)CaMn3 trigonal pyramids, corners with three equivalent O(6)CaMn3 trigonal pyramids,  an edgeedge with one O(3)Ca2Mn2 trigonal pyramid, and edges with two equivalent O(5)Ca2Mn2 trigonal pyramids. In the seventh O site, O(7) is bonded to one Ca(1), one Mn(1), and two equivalent Mn(4) atoms to form distorted OCaMn3 trigonal pyramids that share  a cornercorner with one O(1)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(3)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(4)CaMn3 trigonal pyramid, corners with two equivalent O(8)Ca2Mn2 trigonal pyramids, corners with three equivalent O(2)CaMn3 trigonal pyramids, corners with three equivalent O(7)CaMn3 trigonal pyramids,  an edgeedge with one O(1)Ca2Mn2 trigonal pyramid, and edges with two equivalent O(8)Ca2Mn2 trigonal pyramids. In the eighth O site, O(8) is bonded to one Ca(1), one Ca(3), and two equivalent Mn(4) atoms to form OCa2Mn2 trigonal pyramids that share  a cornercorner with one O(3)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(5)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  a cornercorner with one O(4)CaMn3 trigonal pyramid, corners with two equivalent O(7)CaMn3 trigonal pyramids, corners with three equivalent O(1)Ca2Mn2 trigonal pyramids, corners with three equivalent O(8)Ca2Mn2 trigonal pyramids,  an edgeedge with one O(2)CaMn3 trigonal pyramid, and edges with two equivalent O(7)CaMn3 trigonal pyramids.
CaMn2O4 crystallizes in the monoclinic C2 space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent O(1), two equivalent O(7), and two equivalent O(8) atoms to form distorted CaO6 octahedra that share corners with four equivalent Ca(3)O6 octahedra, corners with two equivalent Mn(2)O5 square pyramids, corners with four equivalent Mn(4)O5 square pyramids, edges with two equivalent Mn(1)O5 square pyramids, and edges with two equivalent Mn(4)O5 square pyramids. The corner-sharing octahedral tilt angles range from 46-48°. Both Ca(1)-O(1) bond lengths are 2.32 Å. Both Ca(1)-O(7) bond lengths are 2.45 Å. Both Ca(1)-O(8) bond lengths are 2.31 Å. In the second Ca site, Ca(2) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms to form CaO6 octahedra that share corners with four equivalent Ca(3)O6 octahedra, corners with two equivalent Mn(1)O5 square pyramids, corners with four equivalent Mn(3)O5 square pyramids, edges with two equivalent Mn(2)O5 square pyramids, and edges with two equivalent Mn(3)O5 square pyramids. The corner-sharing octahedral tilt angles range from 47-49°. Both Ca(2)-O(3) bond lengths are 2.33 Å. Both Ca(2)-O(5) bond lengths are 2.31 Å. Both Ca(2)-O(6) bond lengths are 2.42 Å. In the third Ca site, Ca(3) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(8) atom to form CaO6 octahedra that share corners with two equivalent Ca(1)O6 octahedra, corners with two equivalent Ca(2)O6 octahedra,  a cornercorner with one Mn(3)O5 square pyramid,  a cornercorner with one Mn(4)O5 square pyramid, corners with two equivalent Mn(1)O5 square pyramids, corners with two equivalent Mn(2)O5 square pyramids,  an edgeedge with one Mn(1)O5 square pyramid,  an edgeedge with one Mn(2)O5 square pyramid,  an edgeedge with one Mn(3)O5 square pyramid, and  an edgeedge with one Mn(4)O5 square pyramid. The corner-sharing octahedral tilt angles range from 46-49°. The Ca(3)-O(1) bond length is 2.39 Å. The Ca(3)-O(2) bond length is 2.36 Å. The Ca(3)-O(3) bond length is 2.36 Å. The Ca(3)-O(4) bond length is 2.37 Å. The Ca(3)-O(5) bond length is 2.29 Å. The Ca(3)-O(8) bond length is 2.31 Å. There are four inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(7) atom to form distorted MnO5 square pyramids that share  a cornercorner with one Ca(2)O6 octahedra, corners with two equivalent Ca(3)O6 octahedra,  a cornercorner with one Mn(3)O5 square pyramid, corners with three equivalent Mn(4)O5 square pyramids,  an edgeedge with one Ca(1)O6 octahedra,  an edgeedge with one Ca(3)O6 octahedra, and edges with two equivalent Mn(2)O5 square pyramids. The corner-sharing octahedral tilt angles range from 59-71°. The Mn(1)-O(1) bond length is 1.98 Å. The Mn(1)-O(2) bond length is 2.00 Å. The Mn(1)-O(3) bond length is 1.95 Å. The Mn(1)-O(4) bond length is 1.95 Å. The Mn(1)-O(7) bond length is 2.26 Å. In the second Mn site, Mn(2) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(6) atom to form distorted MnO5 square pyramids that share  a cornercorner with one Ca(1)O6 octahedra, corners with two equivalent Ca(3)O6 octahedra,  a cornercorner with one Mn(4)O5 square pyramid, corners with three equivalent Mn(3)O5 square pyramids,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Ca(3)O6 octahedra, and edges with two equivalent Mn(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 59-76°. The Mn(2)-O(1) bond length is 1.95 Å. The Mn(2)-O(2) bond length is 1.94 Å. The Mn(2)-O(3) bond length is 1.97 Å. The Mn(2)-O(4) bond length is 1.99 Å. The Mn(2)-O(6) bond length is 2.32 Å. In the third Mn site, Mn(3) is bonded to one O(4), two equivalent O(5), and two equivalent O(6) atoms to form distorted MnO5 square pyramids that share  a cornercorner with one Ca(3)O6 octahedra, corners with two equivalent Ca(2)O6 octahedra,  a cornercorner with one Mn(1)O5 square pyramid, corners with three equivalent Mn(2)O5 square pyramids,  an edgeedge with one Ca(2)O6 octahedra,  an edgeedge with one Ca(3)O6 octahedra, and edges with two equivalent Mn(3)O5 square pyramids. The corner-sharing octahedral tilt angles range from 57-71°. The Mn(3)-O(4) bond length is 2.34 Å. There is one shorter (1.91 Å) and one longer (1.95 Å) Mn(3)-O(5) bond length. There is one shorter (1.98 Å) and one longer (2.01 Å) Mn(3)-O(6) bond length. In the fourth Mn site, Mn(4) is bonded to one O(2), two equivalent O(7), and two equivalent O(8) atoms to form distorted MnO5 square pyramids that share  a cornercorner with one Ca(3)O6 octahedra, corners with two equivalent Ca(1)O6 octahedra,  a cornercorner with one Mn(2)O5 square pyramid, corners with three equivalent Mn(1)O5 square pyramids,  an edgeedge with one Ca(1)O6 octahedra,  an edgeedge with one Ca(3)O6 octahedra, and edges with two equivalent Mn(4)O5 square pyramids. The corner-sharing octahedral tilt angles range from 56-69°. The Mn(4)-O(2) bond length is 2.36 Å. There is one shorter (1.96 Å) and one longer (2.00 Å) Mn(4)-O(7) bond length. There is one shorter (1.91 Å) and one longer (1.95 Å) Mn(4)-O(8) bond length. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ca(3), one Mn(1), and one Mn(2) atom to form OCa2Mn2 trigonal pyramids that share  a cornercorner with one O(1)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(3)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(5)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  a cornercorner with one O(6)CaMn3 trigonal pyramid,  a cornercorner with one O(7)CaMn3 trigonal pyramid, corners with three equivalent O(8)Ca2Mn2 trigonal pyramids, corners with three equivalent O(4)CaMn3 trigonal pyramids,  an edgeedge with one O(3)Ca2Mn2 trigonal pyramid,  an edgeedge with one O(2)CaMn3 trigonal pyramid, and  an edgeedge with one O(7)CaMn3 trigonal pyramid. In the second O site, O(2) is bonded to one Ca(3), one Mn(1), one Mn(2), and one Mn(4) atom to form distorted OCaMn3 trigonal pyramids that share  a cornercorner with one O(1)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(5)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(8)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(4)CaMn3 trigonal pyramid,  a cornercorner with one O(6)CaMn3 trigonal pyramid, corners with three equivalent O(3)Ca2Mn2 trigonal pyramids, corners with three equivalent O(7)CaMn3 trigonal pyramids,  an edgeedge with one O(1)Ca2Mn2 trigonal pyramid,  an edgeedge with one O(8)Ca2Mn2 trigonal pyramid, and  an edgeedge with one O(4)CaMn3 trigonal pyramid. In the third O site, O(3) is bonded to one Ca(2), one Ca(3), one Mn(1), and one Mn(2) atom to form OCa2Mn2 trigonal pyramids that share  a cornercorner with one O(1)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(3)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(8)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(4)CaMn3 trigonal pyramid,  a cornercorner with one O(6)CaMn3 trigonal pyramid,  a cornercorner with one O(7)CaMn3 trigonal pyramid, corners with three equivalent O(5)Ca2Mn2 trigonal pyramids, corners with three equivalent O(2)CaMn3 trigonal pyramids,  an edgeedge with one O(1)Ca2Mn2 trigonal pyramid,  an edgeedge with one O(4)CaMn3 trigonal pyramid, and  an edgeedge with one O(6)CaMn3 trigonal pyramid. In the fourth O site, O(4) is bonded to one Ca(3), one Mn(1), one Mn(2), and one Mn(3) atom to form distorted OCaMn3 trigonal pyramids that share  a cornercorner with one O(3)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(5)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(8)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  a cornercorner with one O(7)CaMn3 trigonal pyramid, corners with three equivalent O(1)Ca2Mn2 trigonal pyramids, corners with three equivalent O(6)CaMn3 trigonal pyramids,  an edgeedge with one O(3)Ca2Mn2 trigonal pyramid,  an edgeedge with one O(5)Ca2Mn2 trigonal pyramid, and  an edgeedge with one O(2)CaMn3 trigonal pyramid. In the fifth O site, O(5) is bonded to one Ca(2), one Ca(3), and two equivalent Mn(3) atoms to form OCa2Mn2 trigonal pyramids that share  a cornercorner with one O(1)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(8)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  a cornercorner with one O(4)CaMn3 trigonal pyramid, corners with two equivalent O(6)CaMn3 trigonal pyramids, corners with three equivalent O(3)Ca2Mn2 trigonal pyramids, corners with three equivalent O(5)Ca2Mn2 trigonal pyramids,  an edgeedge with one O(4)CaMn3 trigonal pyramid, and edges with two equivalent O(6)CaMn3 trigonal pyramids. In the sixth O site, O(6) is bonded to one Ca(2), one Mn(2), and two equivalent Mn(3) atoms to form distorted OCaMn3 trigonal pyramids that share  a cornercorner with one O(1)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(3)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(2)CaMn3 trigonal pyramid, corners with two equivalent O(5)Ca2Mn2 trigonal pyramids, corners with three equivalent O(4)CaMn3 trigonal pyramids, corners with three equivalent O(6)CaMn3 trigonal pyramids,  an edgeedge with one O(3)Ca2Mn2 trigonal pyramid, and edges with two equivalent O(5)Ca2Mn2 trigonal pyramids. In the seventh O site, O(7) is bonded to one Ca(1), one Mn(1), and two equivalent Mn(4) atoms to form distorted OCaMn3 trigonal pyramids that share  a cornercorner with one O(1)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(3)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(4)CaMn3 trigonal pyramid, corners with two equivalent O(8)Ca2Mn2 trigonal pyramids, corners with three equivalent O(2)CaMn3 trigonal pyramids, corners with three equivalent O(7)CaMn3 trigonal pyramids,  an edgeedge with one O(1)Ca2Mn2 trigonal pyramid, and edges with two equivalent O(8)Ca2Mn2 trigonal pyramids. In the eighth O site, O(8) is bonded to one Ca(1), one Ca(3), and two equivalent Mn(4) atoms to form OCa2Mn2 trigonal pyramids that share  a cornercorner with one O(3)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(5)Ca2Mn2 trigonal pyramid,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  a cornercorner with one O(4)CaMn3 trigonal pyramid, corners with two equivalent O(7)CaMn3 trigonal pyramids, corners with three equivalent O(1)Ca2Mn2 trigonal pyramids, corners with three equivalent O(8)Ca2Mn2 trigonal pyramids,  an edgeedge with one O(2)CaMn3 trigonal pyramid, and edges with two equivalent O(7)CaMn3 trigonal pyramids.