CaMn2O4 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(1), one O(2), one O(5), one O(6), one O(7), and one O(8) atom to form distorted CaO6 pentagonal pyramids that share corners with three equivalent Mn(1)O6 octahedra, corners with three equivalent Mn(2)O6 octahedra,  an edgeedge with one Mn(1)O6 octahedra,  an edgeedge with one Mn(2)O6 octahedra,  an edgeedge with one Mn(3)O6 octahedra,  an edgeedge with one Mn(4)O6 octahedra,  an edgeedge with one Mn(5)O6 octahedra, and  an edgeedge with one Mn(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-24°. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom. There are six inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), one O(3), two equivalent O(5), and two equivalent O(7) atoms to form distorted MnO6 octahedra that share corners with three equivalent Ca(1)O6 pentagonal pyramids, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Mn(3)O6 octahedra, edges with two equivalent Mn(5)O6 octahedra, and  an edgeedge with one Ca(1)O6 pentagonal pyramid. In the second Mn site, Mn(2) is bonded to one O(2), one O(4), two equivalent O(6), and two equivalent O(8) atoms to form distorted MnO6 octahedra that share corners with three equivalent Ca(1)O6 pentagonal pyramids, edges with two equivalent Mn(2)O6 octahedra, edges with two equivalent Mn(4)O6 octahedra, edges with two equivalent Mn(6)O6 octahedra, and  an edgeedge with one Ca(1)O6 pentagonal pyramid. In the third Mn site, Mn(3) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form MnO6 octahedra that share edges with two equivalent Mn(5)O6 octahedra, edges with four equivalent Mn(1)O6 octahedra, and edges with two equivalent Ca(1)O6 pentagonal pyramids. In the fourth Mn site, Mn(4) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form MnO6 octahedra that share edges with two equivalent Mn(6)O6 octahedra, edges with four equivalent Mn(2)O6 octahedra, and edges with two equivalent Ca(1)O6 pentagonal pyramids. In the fifth Mn site, Mn(5) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(7) atoms to form MnO6 octahedra that share edges with two equivalent Mn(3)O6 octahedra, edges with four equivalent Mn(1)O6 octahedra, and edges with two equivalent Ca(1)O6 pentagonal pyramids. In the sixth Mn site, Mn(6) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(8) atoms to form MnO6 octahedra that share edges with two equivalent Mn(4)O6 octahedra, edges with four equivalent Mn(2)O6 octahedra, and edges with two equivalent Ca(1)O6 pentagonal pyramids. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Ca(1), one Mn(1), one Mn(3), and one Mn(5) atom. In the second O site, O(2) is bonded to one Ca(1), one Mn(2), one Mn(4), and one Mn(6) atom to form OCaMn3 trigonal pyramids that share  a cornercorner with one O(5)Ca2Mn3 trigonal bipyramid,  a cornercorner with one O(6)Ca2Mn3 trigonal bipyramid,  a cornercorner with one O(7)Ca2Mn3 trigonal bipyramid,  a cornercorner with one O(8)Ca2Mn3 trigonal bipyramid, corners with two equivalent O(2)CaMn3 trigonal pyramids, edges with two equivalent O(6)Ca2Mn3 trigonal bipyramids, and edges with two equivalent O(8)Ca2Mn3 trigonal bipyramids. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Ca(2), one Mn(1), one Mn(3), and one Mn(5) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Ca(2), one Mn(2), one Mn(4), and one Mn(6) atom. In the fifth O site, O(5) is bonded to one Ca(1), one Ca(2), one Mn(3), and two equivalent Mn(1) atoms to form distorted OCa2Mn3 trigonal bipyramids that share  a cornercorner with one O(5)Ca2Mn3 trigonal bipyramid, corners with two equivalent O(6)Ca2Mn3 trigonal bipyramids, corners with two equivalent O(7)Ca2Mn3 trigonal bipyramids,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  an edgeedge with one O(5)Ca2Mn3 trigonal bipyramid,  an edgeedge with one O(8)Ca2Mn3 trigonal bipyramid, and edges with two equivalent O(7)Ca2Mn3 trigonal bipyramids. In the sixth O site, O(6) is bonded to one Ca(1), one Ca(2), one Mn(4), and two equivalent Mn(2) atoms to form OCa2Mn3 trigonal bipyramids that share  a cornercorner with one O(6)Ca2Mn3 trigonal bipyramid, corners with two equivalent O(5)Ca2Mn3 trigonal bipyramids, corners with two equivalent O(8)Ca2Mn3 trigonal bipyramids,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  an edgeedge with one O(6)Ca2Mn3 trigonal bipyramid,  an edgeedge with one O(7)Ca2Mn3 trigonal bipyramid, edges with two equivalent O(8)Ca2Mn3 trigonal bipyramids, and edges with two equivalent O(2)CaMn3 trigonal pyramids. In the seventh O site, O(7) is bonded to one Ca(1), one Ca(2), one Mn(5), and two equivalent Mn(1) atoms to form OCa2Mn3 trigonal bipyramids that share  a cornercorner with one O(7)Ca2Mn3 trigonal bipyramid, corners with two equivalent O(5)Ca2Mn3 trigonal bipyramids, corners with two equivalent O(8)Ca2Mn3 trigonal bipyramids,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  an edgeedge with one O(6)Ca2Mn3 trigonal bipyramid,  an edgeedge with one O(7)Ca2Mn3 trigonal bipyramid, and edges with two equivalent O(5)Ca2Mn3 trigonal bipyramids. In the eighth O site, O(8) is bonded to one Ca(1), one Ca(2), one Mn(6), and two equivalent Mn(2) atoms to form distorted OCa2Mn3 trigonal bipyramids that share  a cornercorner with one O(8)Ca2Mn3 trigonal bipyramid, corners with two equivalent O(6)Ca2Mn3 trigonal bipyramids, corners with two equivalent O(7)Ca2Mn3 trigonal bipyramids,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  an edgeedge with one O(5)Ca2Mn3 trigonal bipyramid,  an edgeedge with one O(8)Ca2Mn3 trigonal bipyramid, edges with two equivalent O(6)Ca2Mn3 trigonal bipyramids, and edges with two equivalent O(2)CaMn3 trigonal pyramids.
CaMn2O4 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(1), one O(2), one O(5), one O(6), one O(7), and one O(8) atom to form distorted CaO6 pentagonal pyramids that share corners with three equivalent Mn(1)O6 octahedra, corners with three equivalent Mn(2)O6 octahedra,  an edgeedge with one Mn(1)O6 octahedra,  an edgeedge with one Mn(2)O6 octahedra,  an edgeedge with one Mn(3)O6 octahedra,  an edgeedge with one Mn(4)O6 octahedra,  an edgeedge with one Mn(5)O6 octahedra, and  an edgeedge with one Mn(6)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-24°. The Ca(1)-O(1) bond length is 2.30 Å. The Ca(1)-O(2) bond length is 2.32 Å. The Ca(1)-O(5) bond length is 2.41 Å. The Ca(1)-O(6) bond length is 2.48 Å. The Ca(1)-O(7) bond length is 2.49 Å. The Ca(1)-O(8) bond length is 2.40 Å. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom. The Ca(2)-O(3) bond length is 2.36 Å. The Ca(2)-O(4) bond length is 2.39 Å. The Ca(2)-O(5) bond length is 2.43 Å. The Ca(2)-O(6) bond length is 2.44 Å. The Ca(2)-O(7) bond length is 2.44 Å. The Ca(2)-O(8) bond length is 2.44 Å. There are six inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), one O(3), two equivalent O(5), and two equivalent O(7) atoms to form distorted MnO6 octahedra that share corners with three equivalent Ca(1)O6 pentagonal pyramids, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Mn(3)O6 octahedra, edges with two equivalent Mn(5)O6 octahedra, and  an edgeedge with one Ca(1)O6 pentagonal pyramid. The Mn(1)-O(1) bond length is 1.94 Å. The Mn(1)-O(3) bond length is 1.94 Å. There is one shorter (1.98 Å) and one longer (2.44 Å) Mn(1)-O(5) bond length. There is one shorter (2.05 Å) and one longer (2.23 Å) Mn(1)-O(7) bond length. In the second Mn site, Mn(2) is bonded to one O(2), one O(4), two equivalent O(6), and two equivalent O(8) atoms to form distorted MnO6 octahedra that share corners with three equivalent Ca(1)O6 pentagonal pyramids, edges with two equivalent Mn(2)O6 octahedra, edges with two equivalent Mn(4)O6 octahedra, edges with two equivalent Mn(6)O6 octahedra, and  an edgeedge with one Ca(1)O6 pentagonal pyramid. The Mn(2)-O(2) bond length is 1.95 Å. The Mn(2)-O(4) bond length is 1.95 Å. There is one shorter (2.03 Å) and one longer (2.31 Å) Mn(2)-O(6) bond length. There is one shorter (1.95 Å) and one longer (2.43 Å) Mn(2)-O(8) bond length. In the third Mn site, Mn(3) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form MnO6 octahedra that share edges with two equivalent Mn(5)O6 octahedra, edges with four equivalent Mn(1)O6 octahedra, and edges with two equivalent Ca(1)O6 pentagonal pyramids. Both Mn(3)-O(1) bond lengths are 2.25 Å. Both Mn(3)-O(3) bond lengths are 1.96 Å. Both Mn(3)-O(5) bond lengths are 2.03 Å. In the fourth Mn site, Mn(4) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form MnO6 octahedra that share edges with two equivalent Mn(6)O6 octahedra, edges with four equivalent Mn(2)O6 octahedra, and edges with two equivalent Ca(1)O6 pentagonal pyramids. Both Mn(4)-O(2) bond lengths are 2.21 Å. Both Mn(4)-O(4) bond lengths are 2.03 Å. Both Mn(4)-O(6) bond lengths are 1.97 Å. In the fifth Mn site, Mn(5) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(7) atoms to form MnO6 octahedra that share edges with two equivalent Mn(3)O6 octahedra, edges with four equivalent Mn(1)O6 octahedra, and edges with two equivalent Ca(1)O6 pentagonal pyramids. Both Mn(5)-O(1) bond lengths are 1.95 Å. Both Mn(5)-O(3) bond lengths are 2.29 Å. Both Mn(5)-O(7) bond lengths are 2.01 Å. In the sixth Mn site, Mn(6) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(8) atoms to form MnO6 octahedra that share edges with two equivalent Mn(4)O6 octahedra, edges with four equivalent Mn(2)O6 octahedra, and edges with two equivalent Ca(1)O6 pentagonal pyramids. Both Mn(6)-O(2) bond lengths are 1.96 Å. Both Mn(6)-O(4) bond lengths are 2.19 Å. Both Mn(6)-O(8) bond lengths are 2.05 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Ca(1), one Mn(1), one Mn(3), and one Mn(5) atom. In the second O site, O(2) is bonded to one Ca(1), one Mn(2), one Mn(4), and one Mn(6) atom to form OCaMn3 trigonal pyramids that share  a cornercorner with one O(5)Ca2Mn3 trigonal bipyramid,  a cornercorner with one O(6)Ca2Mn3 trigonal bipyramid,  a cornercorner with one O(7)Ca2Mn3 trigonal bipyramid,  a cornercorner with one O(8)Ca2Mn3 trigonal bipyramid, corners with two equivalent O(2)CaMn3 trigonal pyramids, edges with two equivalent O(6)Ca2Mn3 trigonal bipyramids, and edges with two equivalent O(8)Ca2Mn3 trigonal bipyramids. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Ca(2), one Mn(1), one Mn(3), and one Mn(5) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Ca(2), one Mn(2), one Mn(4), and one Mn(6) atom. In the fifth O site, O(5) is bonded to one Ca(1), one Ca(2), one Mn(3), and two equivalent Mn(1) atoms to form distorted OCa2Mn3 trigonal bipyramids that share  a cornercorner with one O(5)Ca2Mn3 trigonal bipyramid, corners with two equivalent O(6)Ca2Mn3 trigonal bipyramids, corners with two equivalent O(7)Ca2Mn3 trigonal bipyramids,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  an edgeedge with one O(5)Ca2Mn3 trigonal bipyramid,  an edgeedge with one O(8)Ca2Mn3 trigonal bipyramid, and edges with two equivalent O(7)Ca2Mn3 trigonal bipyramids. In the sixth O site, O(6) is bonded to one Ca(1), one Ca(2), one Mn(4), and two equivalent Mn(2) atoms to form OCa2Mn3 trigonal bipyramids that share  a cornercorner with one O(6)Ca2Mn3 trigonal bipyramid, corners with two equivalent O(5)Ca2Mn3 trigonal bipyramids, corners with two equivalent O(8)Ca2Mn3 trigonal bipyramids,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  an edgeedge with one O(6)Ca2Mn3 trigonal bipyramid,  an edgeedge with one O(7)Ca2Mn3 trigonal bipyramid, edges with two equivalent O(8)Ca2Mn3 trigonal bipyramids, and edges with two equivalent O(2)CaMn3 trigonal pyramids. In the seventh O site, O(7) is bonded to one Ca(1), one Ca(2), one Mn(5), and two equivalent Mn(1) atoms to form OCa2Mn3 trigonal bipyramids that share  a cornercorner with one O(7)Ca2Mn3 trigonal bipyramid, corners with two equivalent O(5)Ca2Mn3 trigonal bipyramids, corners with two equivalent O(8)Ca2Mn3 trigonal bipyramids,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  an edgeedge with one O(6)Ca2Mn3 trigonal bipyramid,  an edgeedge with one O(7)Ca2Mn3 trigonal bipyramid, and edges with two equivalent O(5)Ca2Mn3 trigonal bipyramids. In the eighth O site, O(8) is bonded to one Ca(1), one Ca(2), one Mn(6), and two equivalent Mn(2) atoms to form distorted OCa2Mn3 trigonal bipyramids that share  a cornercorner with one O(8)Ca2Mn3 trigonal bipyramid, corners with two equivalent O(6)Ca2Mn3 trigonal bipyramids, corners with two equivalent O(7)Ca2Mn3 trigonal bipyramids,  a cornercorner with one O(2)CaMn3 trigonal pyramid,  an edgeedge with one O(5)Ca2Mn3 trigonal bipyramid,  an edgeedge with one O(8)Ca2Mn3 trigonal bipyramid, edges with two equivalent O(6)Ca2Mn3 trigonal bipyramids, and edges with two equivalent O(2)CaMn3 trigonal pyramids.