Co2Zn3(Si2O7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted CoO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Zn(1)O5 square pyramids, and  an edgeedge with one Zn(2)O4 tetrahedra. In the second Co site, Co(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form CoO6 octahedra that share corners with two equivalent Zn(1)O5 square pyramids, corners with two equivalent Zn(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Co(1)O6 octahedra, and edges with two equivalent Zn(1)O5 square pyramids. There are two inequivalent Zn sites. In the first Zn site, Zn(1) is bonded to one O(1), one O(2), one O(4), and two equivalent O(7) atoms to form distorted ZnO5 square pyramids that share  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one Zn(2)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra,  an edgeedge with one Co(2)O6 octahedra, and  an edgeedge with one Zn(1)O5 square pyramid. The corner-sharing octahedral tilt angles are 44°. In the second Zn site, Zn(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted ZnO4 tetrahedra that share corners with two equivalent Co(2)O6 octahedra, corners with two equivalent Zn(1)O5 square pyramids, corners with four equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Co(1)O6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra, corners with three equivalent Zn(1)O5 square pyramids, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-61°. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one Zn(1)O5 square pyramid, corners with two equivalent Zn(2)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 61-72°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Co(2), one Zn(1), one Zn(2), and one Si(2) atom to form distorted corner-sharing OZn2CoSi tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one Zn(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Co(1), one Zn(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Co(1), one Co(2), one Zn(1), and one Si(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Zn(1) and one Si(1) atom.
Co2Zn3(Si2O7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted CoO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Zn(1)O5 square pyramids, and  an edgeedge with one Zn(2)O4 tetrahedra. Both Co(1)-O(2) bond lengths are 1.88 Å. Both Co(1)-O(3) bond lengths are 1.95 Å. Both Co(1)-O(4) bond lengths are 2.30 Å. In the second Co site, Co(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form CoO6 octahedra that share corners with two equivalent Zn(1)O5 square pyramids, corners with two equivalent Zn(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Co(1)O6 octahedra, and edges with two equivalent Zn(1)O5 square pyramids. Both Co(2)-O(1) bond lengths are 2.28 Å. Both Co(2)-O(2) bond lengths are 1.84 Å. Both Co(2)-O(4) bond lengths are 2.04 Å. There are two inequivalent Zn sites. In the first Zn site, Zn(1) is bonded to one O(1), one O(2), one O(4), and two equivalent O(7) atoms to form distorted ZnO5 square pyramids that share  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one Zn(2)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra,  an edgeedge with one Co(2)O6 octahedra, and  an edgeedge with one Zn(1)O5 square pyramid. The corner-sharing octahedral tilt angles are 44°. The Zn(1)-O(1) bond length is 2.13 Å. The Zn(1)-O(2) bond length is 2.05 Å. The Zn(1)-O(4) bond length is 2.33 Å. There is one shorter (2.03 Å) and one longer (2.20 Å) Zn(1)-O(7) bond length. In the second Zn site, Zn(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted ZnO4 tetrahedra that share corners with two equivalent Co(2)O6 octahedra, corners with two equivalent Zn(1)O5 square pyramids, corners with four equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Co(1)O6 octahedra. The corner-sharing octahedral tilt angles are 55°. Both Zn(2)-O(1) bond lengths are 2.05 Å. Both Zn(2)-O(3) bond lengths are 2.04 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra, corners with three equivalent Zn(1)O5 square pyramids, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-61°. The Si(1)-O(4) bond length is 1.64 Å. The Si(1)-O(5) bond length is 1.64 Å. The Si(1)-O(6) bond length is 1.64 Å. The Si(1)-O(7) bond length is 1.63 Å. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one Zn(1)O5 square pyramid, corners with two equivalent Zn(2)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 61-72°. The Si(2)-O(1) bond length is 1.67 Å. The Si(2)-O(3) bond length is 1.64 Å. The Si(2)-O(5) bond length is 1.64 Å. The Si(2)-O(6) bond length is 1.64 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Co(2), one Zn(1), one Zn(2), and one Si(2) atom to form distorted corner-sharing OZn2CoSi tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one Zn(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Co(1), one Zn(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Co(1), one Co(2), one Zn(1), and one Si(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Zn(1) and one Si(1) atom.