CaCoSi2O7 crystallizes in the monoclinic P2 space group. Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(6), one O(8), and two equivalent O(5) atoms. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form CoO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. In the second Co site, Co(2) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form CoO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(5), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(1)O4 tetrahedra,  a cornercorner with one Co(2)O4 tetrahedra, and  a cornercorner with one Si(1)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(2), one O(4), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(1)O4 tetrahedra,  a cornercorner with one Co(2)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one Co(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Co(1), and one Si(2) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one Co(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ca(1), one Co(2), and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to two equivalent Ca(1) and one Si(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Ca(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to two equivalent Si(2) atoms. In the eighth O site, O(8) is bonded in a distorted tetrahedral geometry to two equivalent Ca(1) and two equivalent Si(1) atoms.
CaCoSi2O7 crystallizes in the monoclinic P2 space group. Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(6), one O(8), and two equivalent O(5) atoms. The Ca(1)-O(1) bond length is 3.01 Å. The Ca(1)-O(2) bond length is 2.47 Å. The Ca(1)-O(3) bond length is 2.87 Å. The Ca(1)-O(4) bond length is 2.39 Å. The Ca(1)-O(6) bond length is 2.22 Å. The Ca(1)-O(8) bond length is 2.49 Å. There is one shorter (2.53 Å) and one longer (2.58 Å) Ca(1)-O(5) bond length. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form CoO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. Both Co(1)-O(1) bond lengths are 1.83 Å. Both Co(1)-O(2) bond lengths are 1.86 Å. In the second Co site, Co(2) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form CoO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. Both Co(2)-O(3) bond lengths are 1.86 Å. Both Co(2)-O(4) bond lengths are 1.88 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(5), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(1)O4 tetrahedra,  a cornercorner with one Co(2)O4 tetrahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The Si(1)-O(1) bond length is 1.63 Å. The Si(1)-O(3) bond length is 1.62 Å. The Si(1)-O(5) bond length is 1.66 Å. The Si(1)-O(8) bond length is 1.69 Å. In the second Si site, Si(2) is bonded to one O(2), one O(4), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(1)O4 tetrahedra,  a cornercorner with one Co(2)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The Si(2)-O(2) bond length is 1.68 Å. The Si(2)-O(4) bond length is 1.67 Å. The Si(2)-O(6) bond length is 1.61 Å. The Si(2)-O(7) bond length is 1.62 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one Co(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Co(1), and one Si(2) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one Co(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ca(1), one Co(2), and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to two equivalent Ca(1) and one Si(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Ca(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to two equivalent Si(2) atoms. In the eighth O site, O(8) is bonded in a distorted tetrahedral geometry to two equivalent Ca(1) and two equivalent Si(1) atoms.