Ca6Sn5S16 crystallizes in the tetragonal I4/mmm space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to four equivalent S(1), four equivalent S(5), and four equivalent S(6) atoms to form distorted CaS12 cuboctahedra that share corners with eight equivalent Ca(1)S12 cuboctahedra, faces with five equivalent Ca(1)S12 cuboctahedra, faces with four equivalent Sn(1)S6 octahedra, and faces with four equivalent Sn(2)S6 octahedra. In the second Ca site, Ca(2) is bonded in a 4-coordinate geometry to four equivalent S(5) atoms. In the third Ca site, Ca(3) is bonded in a 5-coordinate geometry to one S(3) and four equivalent S(4) atoms. There are three inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to two equivalent S(1) and four equivalent S(6) atoms to form SnS6 octahedra that share corners with two equivalent Sn(2)S6 octahedra, corners with four equivalent Sn(1)S6 octahedra, and faces with eight equivalent Ca(1)S12 cuboctahedra. The corner-sharing octahedra are not tilted. In the second Sn site, Sn(2) is bonded to one S(1), one S(2), and four equivalent S(5) atoms to form SnS6 octahedra that share  a cornercorner with one Sn(1)S6 octahedra, corners with four equivalent Sn(2)S6 octahedra, and faces with four equivalent Ca(1)S12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-11°. In the third Sn site, Sn(3) is bonded in a 6-coordinate geometry to one S(2), one S(3), and four equivalent S(4) atoms. There are six inequivalent S sites. In the first S site, S(5) is bonded to two equivalent Ca(1), two equivalent Ca(2), and two equivalent Sn(2) atoms to form a mixture of distorted face, corner, and edge-sharing SCa4Sn2 octahedra. The corner-sharing octahedral tilt angles are 11°. In the second S site, S(6) is bonded in a distorted linear geometry to four equivalent Ca(1) and two equivalent Sn(1) atoms. In the third S site, S(1) is bonded in a linear geometry to four equivalent Ca(1), one Sn(1), and one Sn(2) atom. In the fourth S site, S(2) is bonded in a distorted linear geometry to one Sn(2) and one Sn(3) atom. In the fifth S site, S(3) is bonded in a linear geometry to one Ca(3) and one Sn(3) atom. In the sixth S site, S(4) is bonded in a distorted see-saw-like geometry to two equivalent Ca(3) and two equivalent Sn(3) atoms.
Ca6Sn5S16 crystallizes in the tetragonal I4/mmm space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to four equivalent S(1), four equivalent S(5), and four equivalent S(6) atoms to form distorted CaS12 cuboctahedra that share corners with eight equivalent Ca(1)S12 cuboctahedra, faces with five equivalent Ca(1)S12 cuboctahedra, faces with four equivalent Sn(1)S6 octahedra, and faces with four equivalent Sn(2)S6 octahedra. All Ca(1)-S(1) bond lengths are 3.54 Å. All Ca(1)-S(5) bond lengths are 3.44 Å. All Ca(1)-S(6) bond lengths are 3.49 Å. In the second Ca site, Ca(2) is bonded in a 4-coordinate geometry to four equivalent S(5) atoms. All Ca(2)-S(5) bond lengths are 3.35 Å. In the third Ca site, Ca(3) is bonded in a 5-coordinate geometry to one S(3) and four equivalent S(4) atoms. The Ca(3)-S(3) bond length is 2.74 Å. All Ca(3)-S(4) bond lengths are 3.05 Å. There are three inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to two equivalent S(1) and four equivalent S(6) atoms to form SnS6 octahedra that share corners with two equivalent Sn(2)S6 octahedra, corners with four equivalent Sn(1)S6 octahedra, and faces with eight equivalent Ca(1)S12 cuboctahedra. The corner-sharing octahedra are not tilted. Both Sn(1)-S(1) bond lengths are 2.48 Å. All Sn(1)-S(6) bond lengths are 2.50 Å. In the second Sn site, Sn(2) is bonded to one S(1), one S(2), and four equivalent S(5) atoms to form SnS6 octahedra that share  a cornercorner with one Sn(1)S6 octahedra, corners with four equivalent Sn(2)S6 octahedra, and faces with four equivalent Ca(1)S12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-11°. The Sn(2)-S(1) bond length is 2.55 Å. The Sn(2)-S(2) bond length is 2.42 Å. All Sn(2)-S(5) bond lengths are 2.51 Å. In the third Sn site, Sn(3) is bonded in a 6-coordinate geometry to one S(2), one S(3), and four equivalent S(4) atoms. The Sn(3)-S(2) bond length is 2.72 Å. The Sn(3)-S(3) bond length is 2.37 Å. All Sn(3)-S(4) bond lengths are 2.56 Å. There are six inequivalent S sites. In the first S site, S(5) is bonded to two equivalent Ca(1), two equivalent Ca(2), and two equivalent Sn(2) atoms to form a mixture of distorted face, corner, and edge-sharing SCa4Sn2 octahedra. The corner-sharing octahedral tilt angles are 11°. In the second S site, S(6) is bonded in a distorted linear geometry to four equivalent Ca(1) and two equivalent Sn(1) atoms. In the third S site, S(1) is bonded in a linear geometry to four equivalent Ca(1), one Sn(1), and one Sn(2) atom. In the fourth S site, S(2) is bonded in a distorted linear geometry to one Sn(2) and one Sn(3) atom. In the fifth S site, S(3) is bonded in a linear geometry to one Ca(3) and one Sn(3) atom. In the sixth S site, S(4) is bonded in a distorted see-saw-like geometry to two equivalent Ca(3) and two equivalent Sn(3) atoms.