K4Sn3Se8 crystallizes in the orthorhombic Ccce space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 8-coordinate geometry to four equivalent Se(1) and four equivalent Se(2) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to six equivalent Se(2) atoms. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form edge-sharing SnSe4 tetrahedra. In the second Sn site, Sn(2) is bonded to four equivalent Se(1) atoms to form edge-sharing SnSe4 tetrahedra. There are two inequivalent Se sites. In the first Se site, Se(2) is bonded in a 6-coordinate geometry to two equivalent K(1), three equivalent K(2), and one Sn(1) atom. In the second Se site, Se(1) is bonded to two equivalent K(1), one Sn(1), and one Sn(2) atom to form a mixture of edge and corner-sharing SeK2Sn2 trigonal pyramids.
K4Sn3Se8 crystallizes in the orthorhombic Ccce space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 8-coordinate geometry to four equivalent Se(1) and four equivalent Se(2) atoms. There are two shorter (3.34 Å) and two longer (3.35 Å) K(1)-Se(1) bond lengths. All K(1)-Se(2) bond lengths are 3.60 Å. In the second K site, K(2) is bonded in a 6-coordinate geometry to six equivalent Se(2) atoms. There are a spread of K(2)-Se(2) bond distances ranging from 3.38-3.48 Å. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form edge-sharing SnSe4 tetrahedra. Both Sn(1)-Se(1) bond lengths are 2.64 Å. Both Sn(1)-Se(2) bond lengths are 2.49 Å. In the second Sn site, Sn(2) is bonded to four equivalent Se(1) atoms to form edge-sharing SnSe4 tetrahedra. All Sn(2)-Se(1) bond lengths are 2.55 Å. There are two inequivalent Se sites. In the first Se site, Se(2) is bonded in a 6-coordinate geometry to two equivalent K(1), three equivalent K(2), and one Sn(1) atom. In the second Se site, Se(1) is bonded to two equivalent K(1), one Sn(1), and one Sn(2) atom to form a mixture of edge and corner-sharing SeK2Sn2 trigonal pyramids.