Ca2ZnSi2O7 crystallizes in the tetragonal P-42_1m space group. Ca(1) is bonded in a 8-coordinate geometry to one O(3), three equivalent O(2), and four equivalent O(1) atoms. Zn(1) is bonded to four equivalent O(1) atoms to form ZnO4 tetrahedra that share corners with four equivalent Si(1)O4 tetrahedra. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with two equivalent Zn(1)O4 tetrahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Zn(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to three equivalent Ca(1) and one Si(1) atom. In the third O site, O(3) is bonded in a distorted tetrahedral geometry to two equivalent Ca(1) and two equivalent Si(1) atoms.
Ca2ZnSi2O7 crystallizes in the tetragonal P-42_1m space group. Ca(1) is bonded in a 8-coordinate geometry to one O(3), three equivalent O(2), and four equivalent O(1) atoms. The Ca(1)-O(3) bond length is 2.49 Å. There is one shorter (2.45 Å) and two longer (2.77 Å) Ca(1)-O(2) bond lengths. There are two shorter (2.41 Å) and two longer (2.70 Å) Ca(1)-O(1) bond lengths. Zn(1) is bonded to four equivalent O(1) atoms to form ZnO4 tetrahedra that share corners with four equivalent Si(1)O4 tetrahedra. All Zn(1)-O(1) bond lengths are 1.96 Å. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with two equivalent Zn(1)O4 tetrahedra. The Si(1)-O(2) bond length is 1.61 Å. The Si(1)-O(3) bond length is 1.68 Å. Both Si(1)-O(1) bond lengths are 1.65 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Zn(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to three equivalent Ca(1) and one Si(1) atom. In the third O site, O(3) is bonded in a distorted tetrahedral geometry to two equivalent Ca(1) and two equivalent Si(1) atoms.