Ca3GeSi2O9 crystallizes in the triclinic P-1 space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(7), and one O(9) atom to form distorted CaO6 octahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Ge(1)O4 tetrahedra, edges with two equivalent Ca(2)O6 octahedra, and  an edgeedge with one Si(2)O4 tetrahedra. In the second Ca site, Ca(2) is bonded to one O(1), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form CaO6 octahedra that share  a cornercorner with one Ge(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra, edges with two equivalent Ca(1)O6 octahedra, and  an edgeedge with one Si(2)O4 tetrahedra. In the third Ca site, Ca(3) is bonded in a 7-coordinate geometry to one O(1), one O(5), one O(8), two equivalent O(4), and two equivalent O(9) atoms. Ge(1) is bonded to one O(2), one O(7), one O(8), and one O(9) atom to form GeO4 tetrahedra that share  a cornercorner with one Ca(2)O6 octahedra, corners with three equivalent Ca(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-63°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(4), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(1)O6 octahedra, corners with three equivalent Ca(2)O6 octahedra,  a cornercorner with one Ge(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-60°. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(1)O6 octahedra,  a cornercorner with one Ca(2)O6 octahedra,  a cornercorner with one Ge(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra,  an edgeedge with one Ca(1)O6 octahedra, and  an edgeedge with one Ca(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-54°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Ca(1), one Ca(2), one Ca(3), and one Si(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ge(1), and one Si(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ca(2), and one Si(1) atom. In the fourth O site, O(4) is bonded to one Ca(2), two equivalent Ca(3), and one Si(1) atom to form distorted OCa3Si trigonal pyramids that share corners with four equivalent O(9)Ca3Ge tetrahedra and  an edgeedge with one O(4)Ca3Si trigonal pyramid. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ca(3), and one Si(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Ca(2), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Ca(1), one Ca(2), and one Ge(1) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Ca(3), one Ge(1), and one Si(1) atom. In the ninth O site, O(9) is bonded to one Ca(1), two equivalent Ca(3), and one Ge(1) atom to form distorted OCa3Ge tetrahedra that share corners with four equivalent O(4)Ca3Si trigonal pyramids and  an edgeedge with one O(9)Ca3Ge tetrahedra.
Ca3GeSi2O9 crystallizes in the triclinic P-1 space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(7), and one O(9) atom to form distorted CaO6 octahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Ge(1)O4 tetrahedra, edges with two equivalent Ca(2)O6 octahedra, and  an edgeedge with one Si(2)O4 tetrahedra. The Ca(1)-O(1) bond length is 2.59 Å. The Ca(1)-O(2) bond length is 2.38 Å. The Ca(1)-O(3) bond length is 2.33 Å. The Ca(1)-O(5) bond length is 2.51 Å. The Ca(1)-O(7) bond length is 2.31 Å. The Ca(1)-O(9) bond length is 2.31 Å. In the second Ca site, Ca(2) is bonded to one O(1), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form CaO6 octahedra that share  a cornercorner with one Ge(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra, edges with two equivalent Ca(1)O6 octahedra, and  an edgeedge with one Si(2)O4 tetrahedra. The Ca(2)-O(1) bond length is 2.54 Å. The Ca(2)-O(3) bond length is 2.36 Å. The Ca(2)-O(4) bond length is 2.34 Å. The Ca(2)-O(5) bond length is 2.43 Å. The Ca(2)-O(6) bond length is 2.46 Å. The Ca(2)-O(7) bond length is 2.36 Å. In the third Ca site, Ca(3) is bonded in a 7-coordinate geometry to one O(1), one O(5), one O(8), two equivalent O(4), and two equivalent O(9) atoms. The Ca(3)-O(1) bond length is 2.48 Å. The Ca(3)-O(5) bond length is 2.38 Å. The Ca(3)-O(8) bond length is 2.63 Å. There is one shorter (2.39 Å) and one longer (2.49 Å) Ca(3)-O(4) bond length. There is one shorter (2.35 Å) and one longer (2.46 Å) Ca(3)-O(9) bond length. Ge(1) is bonded to one O(2), one O(7), one O(8), and one O(9) atom to form GeO4 tetrahedra that share  a cornercorner with one Ca(2)O6 octahedra, corners with three equivalent Ca(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-63°. The Ge(1)-O(2) bond length is 1.79 Å. The Ge(1)-O(7) bond length is 1.72 Å. The Ge(1)-O(8) bond length is 1.79 Å. The Ge(1)-O(9) bond length is 1.75 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(4), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(1)O6 octahedra, corners with three equivalent Ca(2)O6 octahedra,  a cornercorner with one Ge(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-60°. The Si(1)-O(3) bond length is 1.62 Å. The Si(1)-O(4) bond length is 1.63 Å. The Si(1)-O(6) bond length is 1.67 Å. The Si(1)-O(8) bond length is 1.65 Å. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(1)O6 octahedra,  a cornercorner with one Ca(2)O6 octahedra,  a cornercorner with one Ge(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra,  an edgeedge with one Ca(1)O6 octahedra, and  an edgeedge with one Ca(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-54°. The Si(2)-O(1) bond length is 1.62 Å. The Si(2)-O(2) bond length is 1.68 Å. The Si(2)-O(5) bond length is 1.63 Å. The Si(2)-O(6) bond length is 1.69 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Ca(1), one Ca(2), one Ca(3), and one Si(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ge(1), and one Si(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ca(2), and one Si(1) atom. In the fourth O site, O(4) is bonded to one Ca(2), two equivalent Ca(3), and one Si(1) atom to form distorted OCa3Si trigonal pyramids that share corners with four equivalent O(9)Ca3Ge tetrahedra and  an edgeedge with one O(4)Ca3Si trigonal pyramid. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ca(3), and one Si(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Ca(2), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Ca(1), one Ca(2), and one Ge(1) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Ca(3), one Ge(1), and one Si(1) atom. In the ninth O site, O(9) is bonded to one Ca(1), two equivalent Ca(3), and one Ge(1) atom to form distorted OCa3Ge tetrahedra that share corners with four equivalent O(4)Ca3Si trigonal pyramids and  an edgeedge with one O(9)Ca3Ge tetrahedra.