Ca3Sn2S7 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to two equivalent S(1) and four equivalent S(3) atoms. In the second Ca site, Ca(2) is bonded to one S(3), two equivalent S(4), and three equivalent S(2) atoms to form distorted CaS6 octahedra that share corners with two equivalent Sn(1)S6 octahedra, corners with eight equivalent Ca(2)S6 octahedra, edges with two equivalent Sn(1)S6 octahedra, and  a faceface with one Sn(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 45-73°. Sn(1) is bonded to one S(1), one S(2), two equivalent S(3), and two equivalent S(4) atoms to form SnS6 octahedra that share corners with two equivalent Ca(2)S6 octahedra, corners with five equivalent Sn(1)S6 octahedra, edges with two equivalent Ca(2)S6 octahedra, and  a faceface with one Ca(2)S6 octahedra. The corner-sharing octahedral tilt angles range from 36-62°. There are four inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Ca(1) and two equivalent Sn(1) atoms to form distorted SCa2Sn2 trigonal pyramids that share corners with two equivalent S(2)Ca3Sn tetrahedra, corners with eight equivalent S(3)Ca3Sn2 trigonal bipyramids, corners with two equivalent S(1)Ca2Sn2 trigonal pyramids, and edges with two equivalent S(3)Ca3Sn2 trigonal bipyramids. In the second S site, S(2) is bonded to three equivalent Ca(2) and one Sn(1) atom to form distorted SCa3Sn tetrahedra that share corners with six equivalent S(2)Ca3Sn tetrahedra,  a cornercorner with one S(3)Ca3Sn2 trigonal bipyramid,  a cornercorner with one S(1)Ca2Sn2 trigonal pyramid, and edges with two equivalent S(3)Ca3Sn2 trigonal bipyramids. In the third S site, S(3) is bonded to one Ca(2), two equivalent Ca(1), and two equivalent Sn(1) atoms to form distorted SCa3Sn2 trigonal bipyramids that share  a cornercorner with one S(2)Ca3Sn tetrahedra, corners with two equivalent S(3)Ca3Sn2 trigonal bipyramids, corners with four equivalent S(1)Ca2Sn2 trigonal pyramids, edges with two equivalent S(2)Ca3Sn tetrahedra, edges with three equivalent S(3)Ca3Sn2 trigonal bipyramids, and  an edgeedge with one S(1)Ca2Sn2 trigonal pyramid. In the fourth S site, S(4) is bonded in a 4-coordinate geometry to two equivalent Ca(2) and two equivalent Sn(1) atoms.
Ca3Sn2S7 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to two equivalent S(1) and four equivalent S(3) atoms. There is one shorter (2.84 Å) and one longer (2.88 Å) Ca(1)-S(1) bond length. There are two shorter (2.88 Å) and two longer (3.03 Å) Ca(1)-S(3) bond lengths. In the second Ca site, Ca(2) is bonded to one S(3), two equivalent S(4), and three equivalent S(2) atoms to form distorted CaS6 octahedra that share corners with two equivalent Sn(1)S6 octahedra, corners with eight equivalent Ca(2)S6 octahedra, edges with two equivalent Sn(1)S6 octahedra, and  a faceface with one Sn(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 45-73°. The Ca(2)-S(3) bond length is 2.99 Å. There is one shorter (2.83 Å) and one longer (2.91 Å) Ca(2)-S(4) bond length. There are two shorter (2.77 Å) and one longer (2.81 Å) Ca(2)-S(2) bond length. Sn(1) is bonded to one S(1), one S(2), two equivalent S(3), and two equivalent S(4) atoms to form SnS6 octahedra that share corners with two equivalent Ca(2)S6 octahedra, corners with five equivalent Sn(1)S6 octahedra, edges with two equivalent Ca(2)S6 octahedra, and  a faceface with one Ca(2)S6 octahedra. The corner-sharing octahedral tilt angles range from 36-62°. The Sn(1)-S(1) bond length is 2.62 Å. The Sn(1)-S(2) bond length is 2.51 Å. There is one shorter (2.58 Å) and one longer (2.69 Å) Sn(1)-S(3) bond length. There is one shorter (2.59 Å) and one longer (2.66 Å) Sn(1)-S(4) bond length. There are four inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Ca(1) and two equivalent Sn(1) atoms to form distorted SCa2Sn2 trigonal pyramids that share corners with two equivalent S(2)Ca3Sn tetrahedra, corners with eight equivalent S(3)Ca3Sn2 trigonal bipyramids, corners with two equivalent S(1)Ca2Sn2 trigonal pyramids, and edges with two equivalent S(3)Ca3Sn2 trigonal bipyramids. In the second S site, S(2) is bonded to three equivalent Ca(2) and one Sn(1) atom to form distorted SCa3Sn tetrahedra that share corners with six equivalent S(2)Ca3Sn tetrahedra,  a cornercorner with one S(3)Ca3Sn2 trigonal bipyramid,  a cornercorner with one S(1)Ca2Sn2 trigonal pyramid, and edges with two equivalent S(3)Ca3Sn2 trigonal bipyramids. In the third S site, S(3) is bonded to one Ca(2), two equivalent Ca(1), and two equivalent Sn(1) atoms to form distorted SCa3Sn2 trigonal bipyramids that share  a cornercorner with one S(2)Ca3Sn tetrahedra, corners with two equivalent S(3)Ca3Sn2 trigonal bipyramids, corners with four equivalent S(1)Ca2Sn2 trigonal pyramids, edges with two equivalent S(2)Ca3Sn tetrahedra, edges with three equivalent S(3)Ca3Sn2 trigonal bipyramids, and  an edgeedge with one S(1)Ca2Sn2 trigonal pyramid. In the fourth S site, S(4) is bonded in a 4-coordinate geometry to two equivalent Ca(2) and two equivalent Sn(1) atoms.