CaMnGe2O6 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and two equivalent O(1) atoms to form distorted CaO7 pentagonal bipyramids that share corners with two equivalent Ca(1)O7 pentagonal bipyramids, corners with four equivalent Ge(1)O4 tetrahedra, corners with three equivalent Ge(2)O5 trigonal bipyramids, edges with three equivalent Mn(1)O6 octahedra, and edges with two equivalent Ge(2)O5 trigonal bipyramids. Mn(1) is bonded to one O(3), one O(4), two equivalent O(5), and two equivalent O(6) atoms to form MnO6 octahedra that share corners with three equivalent Ge(1)O4 tetrahedra, corners with two equivalent Ge(2)O5 trigonal bipyramids, edges with two equivalent Mn(1)O6 octahedra, edges with three equivalent Ca(1)O7 pentagonal bipyramids, and  an edgeedge with one Ge(2)O5 trigonal bipyramid. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to one O(4), one O(5), and two equivalent O(2) atoms to form GeO4 tetrahedra that share corners with three equivalent Mn(1)O6 octahedra, corners with four equivalent Ca(1)O7 pentagonal bipyramids, and corners with two equivalent Ge(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-63°. In the second Ge site, Ge(2) is bonded to one O(6), two equivalent O(1), and two equivalent O(3) atoms to form distorted GeO5 trigonal bipyramids that share corners with two equivalent Mn(1)O6 octahedra, corners with three equivalent Ca(1)O7 pentagonal bipyramids, corners with two equivalent Ge(2)O5 trigonal bipyramids,  an edgeedge with one Mn(1)O6 octahedra, edges with two equivalent Ca(1)O7 pentagonal bipyramids, and  an edgeedge with one Ge(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 41-45°. There are six inequivalent O sites. In the first O site, O(5) is bonded to one Ca(1), two equivalent Mn(1), and one Ge(1) atom to form distorted OCaMn2Ge trigonal pyramids that share corners with two equivalent O(1)Ca2Ge2 tetrahedra,  a cornercorner with one O(6)CaMn2Ge trigonal pyramid, corners with two equivalent O(5)CaMn2Ge trigonal pyramids, and edges with two equivalent O(6)CaMn2Ge trigonal pyramids. In the second O site, O(6) is bonded to one Ca(1), two equivalent Mn(1), and one Ge(2) atom to form distorted OCaMn2Ge trigonal pyramids that share corners with four equivalent O(1)Ca2Ge2 tetrahedra,  a cornercorner with one O(5)CaMn2Ge trigonal pyramid, corners with two equivalent O(6)CaMn2Ge trigonal pyramids, and edges with two equivalent O(5)CaMn2Ge trigonal pyramids. In the third O site, O(1) is bonded to two equivalent Ca(1) and two equivalent Ge(2) atoms to form distorted OCa2Ge2 tetrahedra that share corners with two equivalent O(5)CaMn2Ge trigonal pyramids, corners with four equivalent O(6)CaMn2Ge trigonal pyramids, and edges with two equivalent O(1)Ca2Ge2 tetrahedra. In the fourth O site, O(2) is bonded in a trigonal planar geometry to one Ca(1) and two equivalent Ge(1) atoms. In the fifth O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1), one Mn(1), and two equivalent Ge(2) atoms. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ca(1), one Mn(1), and one Ge(1) atom.
CaMnGe2O6 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and two equivalent O(1) atoms to form distorted CaO7 pentagonal bipyramids that share corners with two equivalent Ca(1)O7 pentagonal bipyramids, corners with four equivalent Ge(1)O4 tetrahedra, corners with three equivalent Ge(2)O5 trigonal bipyramids, edges with three equivalent Mn(1)O6 octahedra, and edges with two equivalent Ge(2)O5 trigonal bipyramids. The Ca(1)-O(2) bond length is 2.50 Å. The Ca(1)-O(3) bond length is 2.60 Å. The Ca(1)-O(4) bond length is 2.34 Å. The Ca(1)-O(5) bond length is 2.47 Å. The Ca(1)-O(6) bond length is 2.41 Å. There is one shorter (2.57 Å) and one longer (2.66 Å) Ca(1)-O(1) bond length. Mn(1) is bonded to one O(3), one O(4), two equivalent O(5), and two equivalent O(6) atoms to form MnO6 octahedra that share corners with three equivalent Ge(1)O4 tetrahedra, corners with two equivalent Ge(2)O5 trigonal bipyramids, edges with two equivalent Mn(1)O6 octahedra, edges with three equivalent Ca(1)O7 pentagonal bipyramids, and  an edgeedge with one Ge(2)O5 trigonal bipyramid. The Mn(1)-O(3) bond length is 2.27 Å. The Mn(1)-O(4) bond length is 2.11 Å. There is one shorter (2.15 Å) and one longer (2.25 Å) Mn(1)-O(5) bond length. There is one shorter (2.14 Å) and one longer (2.22 Å) Mn(1)-O(6) bond length. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to one O(4), one O(5), and two equivalent O(2) atoms to form GeO4 tetrahedra that share corners with three equivalent Mn(1)O6 octahedra, corners with four equivalent Ca(1)O7 pentagonal bipyramids, and corners with two equivalent Ge(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-63°. The Ge(1)-O(4) bond length is 1.72 Å. The Ge(1)-O(5) bond length is 1.76 Å. There is one shorter (1.82 Å) and one longer (1.83 Å) Ge(1)-O(2) bond length. In the second Ge site, Ge(2) is bonded to one O(6), two equivalent O(1), and two equivalent O(3) atoms to form distorted GeO5 trigonal bipyramids that share corners with two equivalent Mn(1)O6 octahedra, corners with three equivalent Ca(1)O7 pentagonal bipyramids, corners with two equivalent Ge(2)O5 trigonal bipyramids,  an edgeedge with one Mn(1)O6 octahedra, edges with two equivalent Ca(1)O7 pentagonal bipyramids, and  an edgeedge with one Ge(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 41-45°. The Ge(2)-O(6) bond length is 1.77 Å. There is one shorter (1.81 Å) and one longer (1.91 Å) Ge(2)-O(1) bond length. There is one shorter (1.77 Å) and one longer (2.37 Å) Ge(2)-O(3) bond length. There are six inequivalent O sites. In the first O site, O(5) is bonded to one Ca(1), two equivalent Mn(1), and one Ge(1) atom to form distorted OCaMn2Ge trigonal pyramids that share corners with two equivalent O(1)Ca2Ge2 tetrahedra,  a cornercorner with one O(6)CaMn2Ge trigonal pyramid, corners with two equivalent O(5)CaMn2Ge trigonal pyramids, and edges with two equivalent O(6)CaMn2Ge trigonal pyramids. In the second O site, O(6) is bonded to one Ca(1), two equivalent Mn(1), and one Ge(2) atom to form distorted OCaMn2Ge trigonal pyramids that share corners with four equivalent O(1)Ca2Ge2 tetrahedra,  a cornercorner with one O(5)CaMn2Ge trigonal pyramid, corners with two equivalent O(6)CaMn2Ge trigonal pyramids, and edges with two equivalent O(5)CaMn2Ge trigonal pyramids. In the third O site, O(1) is bonded to two equivalent Ca(1) and two equivalent Ge(2) atoms to form distorted OCa2Ge2 tetrahedra that share corners with two equivalent O(5)CaMn2Ge trigonal pyramids, corners with four equivalent O(6)CaMn2Ge trigonal pyramids, and edges with two equivalent O(1)Ca2Ge2 tetrahedra. In the fourth O site, O(2) is bonded in a trigonal planar geometry to one Ca(1) and two equivalent Ge(1) atoms. In the fifth O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1), one Mn(1), and two equivalent Ge(2) atoms. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ca(1), one Mn(1), and one Ge(1) atom.