Cu2Zn3(Si2O7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a rectangular see-saw-like geometry to two equivalent O(2) and two equivalent O(3) atoms. In the second Cu site, Cu(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted CuO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with two equivalent Zn(2)O4 trigonal pyramids. There are two inequivalent Zn sites. In the first Zn site, Zn(1) is bonded in a see-saw-like geometry to one O(1), one O(2), one O(4), and one O(7) atom. In the second Zn site, Zn(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted ZnO4 trigonal pyramids that share corners with two equivalent Cu(2)O6 octahedra and corners with four equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 60°. 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 Cu(2)O6 octahedra and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 55°. 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 Cu(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Zn(2)O4 trigonal pyramids. The corner-sharing octahedral tilt angles are 73°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Cu(2), one Zn(1), one Zn(2), and one Si(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Cu(1), one Cu(2), and one Zn(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Cu(1), one Zn(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Cu(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 150 degrees geometry to one Si(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Zn(1) and one Si(1) atom.
Cu2Zn3(Si2O7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a rectangular see-saw-like geometry to two equivalent O(2) and two equivalent O(3) atoms. Both Cu(1)-O(2) bond lengths are 1.83 Å. Both Cu(1)-O(3) bond lengths are 1.91 Å. In the second Cu site, Cu(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted CuO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with two equivalent Zn(2)O4 trigonal pyramids. Both Cu(2)-O(1) bond lengths are 2.49 Å. Both Cu(2)-O(2) bond lengths are 1.84 Å. Both Cu(2)-O(4) bond lengths are 1.99 Å. There are two inequivalent Zn sites. In the first Zn site, Zn(1) is bonded in a see-saw-like geometry to one O(1), one O(2), one O(4), and one O(7) atom. The Zn(1)-O(1) bond length is 2.08 Å. The Zn(1)-O(2) bond length is 2.10 Å. The Zn(1)-O(4) bond length is 2.00 Å. The Zn(1)-O(7) bond length is 1.89 Å. In the second Zn site, Zn(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted ZnO4 trigonal pyramids that share corners with two equivalent Cu(2)O6 octahedra and corners with four equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 60°. Both Zn(2)-O(1) bond lengths are 1.99 Å. Both Zn(2)-O(3) bond lengths are 2.03 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 Cu(2)O6 octahedra and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 55°. The Si(1)-O(4) bond length is 1.67 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 1.60 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 Cu(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Zn(2)O4 trigonal pyramids. The corner-sharing octahedral tilt angles are 73°. The Si(2)-O(1) bond length is 1.65 Å. The Si(2)-O(3) bond length is 1.64 Å. The Si(2)-O(5) bond length is 1.65 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 in a 4-coordinate geometry to one Cu(2), one Zn(1), one Zn(2), and one Si(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Cu(1), one Cu(2), and one Zn(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Cu(1), one Zn(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Cu(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 150 degrees geometry to one Si(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Zn(1) and one Si(1) atom.