Ca3Sn2S7 crystallizes in the orthorhombic Pbam space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a body-centered cubic geometry to four equivalent S(2) and four equivalent S(3) atoms. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to two equivalent S(1), two equivalent S(2), two equivalent S(3), and two equivalent S(4) atoms. Sn(1) is bonded to one S(2), one S(3), one S(4), and two equivalent S(1) atoms to form corner-sharing SnS5 trigonal bipyramids. There are four inequivalent S sites. In the first S site, S(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ca(2) and two equivalent Sn(1) atoms. In the second S site, S(2) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Sn(1) atom to form SCa4Sn square pyramids that share corners with two equivalent S(4)Ca4Sn2 octahedra, corners with two equivalent S(2)Ca4Sn square pyramids, corners with six equivalent S(3)Ca4Sn square pyramids, edges with two equivalent S(3)Ca4Sn square pyramids, edges with three equivalent S(2)Ca4Sn square pyramids,  a faceface with one S(4)Ca4Sn2 octahedra, and  a faceface with one S(3)Ca4Sn square pyramid. The corner-sharing octahedral tilt angles are 59°. In the third S site, S(3) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Sn(1) atom to form SCa4Sn square pyramids that share corners with three equivalent S(4)Ca4Sn2 octahedra, corners with two equivalent S(3)Ca4Sn square pyramids, corners with six equivalent S(2)Ca4Sn square pyramids,  an edgeedge with one S(4)Ca4Sn2 octahedra, edges with two equivalent S(2)Ca4Sn square pyramids, edges with three equivalent S(3)Ca4Sn square pyramids, and  a faceface with one S(2)Ca4Sn square pyramid. The corner-sharing octahedral tilt angles range from 7-33°. In the fourth S site, S(4) is bonded to four equivalent Ca(2) and two equivalent Sn(1) atoms to form SCa4Sn2 octahedra that share corners with four equivalent S(2)Ca4Sn square pyramids, corners with six equivalent S(3)Ca4Sn square pyramids, edges with two equivalent S(4)Ca4Sn2 octahedra, edges with two equivalent S(3)Ca4Sn square pyramids, and faces with two equivalent S(2)Ca4Sn square pyramids.
Ca3Sn2S7 crystallizes in the orthorhombic Pbam space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a body-centered cubic geometry to four equivalent S(2) and four equivalent S(3) atoms. All Ca(1)-S(2) bond lengths are 3.12 Å. All Ca(1)-S(3) bond lengths are 3.11 Å. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to two equivalent S(1), two equivalent S(2), two equivalent S(3), and two equivalent S(4) atoms. There is one shorter (3.01 Å) and one longer (3.30 Å) Ca(2)-S(1) bond length. Both Ca(2)-S(2) bond lengths are 3.05 Å. Both Ca(2)-S(3) bond lengths are 2.92 Å. Both Ca(2)-S(4) bond lengths are 2.95 Å. Sn(1) is bonded to one S(2), one S(3), one S(4), and two equivalent S(1) atoms to form corner-sharing SnS5 trigonal bipyramids. The Sn(1)-S(2) bond length is 2.40 Å. The Sn(1)-S(3) bond length is 2.48 Å. The Sn(1)-S(4) bond length is 2.86 Å. Both Sn(1)-S(1) bond lengths are 2.47 Å. There are four inequivalent S sites. In the first S site, S(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ca(2) and two equivalent Sn(1) atoms. In the second S site, S(2) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Sn(1) atom to form SCa4Sn square pyramids that share corners with two equivalent S(4)Ca4Sn2 octahedra, corners with two equivalent S(2)Ca4Sn square pyramids, corners with six equivalent S(3)Ca4Sn square pyramids, edges with two equivalent S(3)Ca4Sn square pyramids, edges with three equivalent S(2)Ca4Sn square pyramids,  a faceface with one S(4)Ca4Sn2 octahedra, and  a faceface with one S(3)Ca4Sn square pyramid. The corner-sharing octahedral tilt angles are 59°. In the third S site, S(3) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Sn(1) atom to form SCa4Sn square pyramids that share corners with three equivalent S(4)Ca4Sn2 octahedra, corners with two equivalent S(3)Ca4Sn square pyramids, corners with six equivalent S(2)Ca4Sn square pyramids,  an edgeedge with one S(4)Ca4Sn2 octahedra, edges with two equivalent S(2)Ca4Sn square pyramids, edges with three equivalent S(3)Ca4Sn square pyramids, and  a faceface with one S(2)Ca4Sn square pyramid. The corner-sharing octahedral tilt angles range from 7-33°. In the fourth S site, S(4) is bonded to four equivalent Ca(2) and two equivalent Sn(1) atoms to form SCa4Sn2 octahedra that share corners with four equivalent S(2)Ca4Sn square pyramids, corners with six equivalent S(3)Ca4Sn square pyramids, edges with two equivalent S(4)Ca4Sn2 octahedra, edges with two equivalent S(3)Ca4Sn square pyramids, and faces with two equivalent S(2)Ca4Sn square pyramids.