CaSn2O5 crystallizes in the orthorhombic Cmcm space group. Ca(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. Sn(1) is bonded to one O(1), one O(3), and three equivalent O(2) atoms to form a mixture of distorted corner and edge-sharing SnO5 trigonal bipyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ca(1) and two equivalent Sn(1) atoms to form OCa2Sn2 tetrahedra that share corners with two equivalent O(1)Ca2Sn2 tetrahedra, corners with two equivalent O(2)CaSn3 tetrahedra, and edges with four equivalent O(2)CaSn3 tetrahedra. In the second O site, O(2) is bonded to one Ca(1) and three equivalent Sn(1) atoms to form distorted OCaSn3 tetrahedra that share  a cornercorner with one O(1)Ca2Sn2 tetrahedra, corners with three equivalent O(2)CaSn3 tetrahedra, edges with two equivalent O(1)Ca2Sn2 tetrahedra, and edges with two equivalent O(2)CaSn3 tetrahedra. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Ca(1) and one Sn(1) atom.
CaSn2O5 crystallizes in the orthorhombic Cmcm space group. Ca(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. Both Ca(1)-O(1) bond lengths are 2.42 Å. Both Ca(1)-O(2) bond lengths are 2.72 Å. Both Ca(1)-O(3) bond lengths are 2.14 Å. Sn(1) is bonded to one O(1), one O(3), and three equivalent O(2) atoms to form a mixture of distorted corner and edge-sharing SnO5 trigonal bipyramids. The Sn(1)-O(1) bond length is 2.11 Å. The Sn(1)-O(3) bond length is 1.89 Å. All Sn(1)-O(2) bond lengths are 2.14 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ca(1) and two equivalent Sn(1) atoms to form OCa2Sn2 tetrahedra that share corners with two equivalent O(1)Ca2Sn2 tetrahedra, corners with two equivalent O(2)CaSn3 tetrahedra, and edges with four equivalent O(2)CaSn3 tetrahedra. In the second O site, O(2) is bonded to one Ca(1) and three equivalent Sn(1) atoms to form distorted OCaSn3 tetrahedra that share  a cornercorner with one O(1)Ca2Sn2 tetrahedra, corners with three equivalent O(2)CaSn3 tetrahedra, edges with two equivalent O(1)Ca2Sn2 tetrahedra, and edges with two equivalent O(2)CaSn3 tetrahedra. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Ca(1) and one Sn(1) atom.