CaSnP2O7 crystallizes in the triclinic P-1 space group. Ca(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(7), and two equivalent O(4) atoms to form CaO7 pentagonal bipyramids that share  a cornercorner with one Sn(1)O5 square pyramid, corners with three equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra,  an edgeedge with one Ca(1)O7 pentagonal bipyramid, and edges with two equivalent Sn(1)O5 square pyramids. Sn(1) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(7) atom to form distorted SnO5 square pyramids that share  a cornercorner with one Ca(1)O7 pentagonal bipyramid, corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and edges with two equivalent Ca(1)O7 pentagonal bipyramids. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Ca(1)O7 pentagonal bipyramids, corners with three equivalent Sn(1)O5 square pyramids, and  a cornercorner with one P(2)O4 tetrahedra. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with four equivalent Ca(1)O7 pentagonal bipyramids, corners with two equivalent Sn(1)O5 square pyramids, and  a cornercorner with one P(1)O4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(1), one Sn(1), and one P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Ca(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one P(2) atom.
CaSnP2O7 crystallizes in the triclinic P-1 space group. Ca(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(7), and two equivalent O(4) atoms to form CaO7 pentagonal bipyramids that share  a cornercorner with one Sn(1)O5 square pyramid, corners with three equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra,  an edgeedge with one Ca(1)O7 pentagonal bipyramid, and edges with two equivalent Sn(1)O5 square pyramids. The Ca(1)-O(1) bond length is 2.42 Å. The Ca(1)-O(2) bond length is 2.67 Å. The Ca(1)-O(3) bond length is 2.46 Å. The Ca(1)-O(5) bond length is 2.53 Å. The Ca(1)-O(7) bond length is 2.36 Å. There is one shorter (2.35 Å) and one longer (2.46 Å) Ca(1)-O(4) bond length. Sn(1) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(7) atom to form distorted SnO5 square pyramids that share  a cornercorner with one Ca(1)O7 pentagonal bipyramid, corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and edges with two equivalent Ca(1)O7 pentagonal bipyramids. The Sn(1)-O(1) bond length is 2.43 Å. The Sn(1)-O(2) bond length is 2.31 Å. The Sn(1)-O(3) bond length is 2.60 Å. The Sn(1)-O(5) bond length is 2.25 Å. The Sn(1)-O(7) bond length is 2.58 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Ca(1)O7 pentagonal bipyramids, corners with three equivalent Sn(1)O5 square pyramids, and  a cornercorner with one P(2)O4 tetrahedra. The P(1)-O(1) bond length is 1.55 Å. The P(1)-O(2) bond length is 1.54 Å. The P(1)-O(3) bond length is 1.52 Å. The P(1)-O(6) bond length is 1.64 Å. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with four equivalent Ca(1)O7 pentagonal bipyramids, corners with two equivalent Sn(1)O5 square pyramids, and  a cornercorner with one P(1)O4 tetrahedra. The P(2)-O(4) bond length is 1.52 Å. The P(2)-O(5) bond length is 1.56 Å. The P(2)-O(6) bond length is 1.62 Å. The P(2)-O(7) bond length is 1.54 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(1), one Sn(1), and one P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Ca(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one P(2) atom.