KFeSeS crystallizes in the monoclinic C2 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 S(1) atoms. In the second K site, K(2) is bonded to four equivalent Se(1) and four equivalent S(1) atoms to form distorted KSe4S4 hexagonal bipyramids that share corners with four equivalent K(2)Se4S4 hexagonal bipyramids, corners with two equivalent Fe(2)Se2S2 tetrahedra, corners with four equivalent Fe(1)Se2S2 tetrahedra, edges with two equivalent K(2)Se4S4 hexagonal bipyramids, edges with two equivalent Fe(1)Se2S2 tetrahedra, and edges with three equivalent Fe(2)Se2S2 tetrahedra. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Se(1) and two equivalent S(1) atoms to form FeSe2S2 tetrahedra that share corners with four equivalent K(2)Se4S4 hexagonal bipyramids, edges with two equivalent K(2)Se4S4 hexagonal bipyramids, and edges with two equivalent Fe(2)Se2S2 tetrahedra. In the second Fe site, Fe(2) is bonded to two equivalent Se(1) and two equivalent S(1) atoms to form FeSe2S2 tetrahedra that share corners with two equivalent K(2)Se4S4 hexagonal bipyramids, edges with three equivalent K(2)Se4S4 hexagonal bipyramids, and edges with two equivalent Fe(1)Se2S2 tetrahedra. Se(1) is bonded in a 6-coordinate geometry to two equivalent K(1), two equivalent K(2), one Fe(1), and one Fe(2) atom. S(1) is bonded in a 6-coordinate geometry to two equivalent K(1), two equivalent K(2), one Fe(1), and one Fe(2) atom.
KFeSeS crystallizes in the monoclinic C2 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 S(1) atoms. There are two shorter (3.38 Å) and two longer (3.43 Å) K(1)-Se(1) bond lengths. There are two shorter (3.44 Å) and two longer (3.61 Å) K(1)-S(1) bond lengths. In the second K site, K(2) is bonded to four equivalent Se(1) and four equivalent S(1) atoms to form distorted KSe4S4 hexagonal bipyramids that share corners with four equivalent K(2)Se4S4 hexagonal bipyramids, corners with two equivalent Fe(2)Se2S2 tetrahedra, corners with four equivalent Fe(1)Se2S2 tetrahedra, edges with two equivalent K(2)Se4S4 hexagonal bipyramids, edges with two equivalent Fe(1)Se2S2 tetrahedra, and edges with three equivalent Fe(2)Se2S2 tetrahedra. There are two shorter (3.49 Å) and two longer (3.53 Å) K(2)-Se(1) bond lengths. There are two shorter (3.46 Å) and two longer (3.51 Å) K(2)-S(1) bond lengths. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Se(1) and two equivalent S(1) atoms to form FeSe2S2 tetrahedra that share corners with four equivalent K(2)Se4S4 hexagonal bipyramids, edges with two equivalent K(2)Se4S4 hexagonal bipyramids, and edges with two equivalent Fe(2)Se2S2 tetrahedra. Both Fe(1)-Se(1) bond lengths are 2.33 Å. Both Fe(1)-S(1) bond lengths are 2.19 Å. In the second Fe site, Fe(2) is bonded to two equivalent Se(1) and two equivalent S(1) atoms to form FeSe2S2 tetrahedra that share corners with two equivalent K(2)Se4S4 hexagonal bipyramids, edges with three equivalent K(2)Se4S4 hexagonal bipyramids, and edges with two equivalent Fe(1)Se2S2 tetrahedra. Both Fe(2)-Se(1) bond lengths are 2.34 Å. Both Fe(2)-S(1) bond lengths are 2.18 Å. Se(1) is bonded in a 6-coordinate geometry to two equivalent K(1), two equivalent K(2), one Fe(1), and one Fe(2) atom. S(1) is bonded in a 6-coordinate geometry to two equivalent K(1), two equivalent K(2), one Fe(1), and one Fe(2) atom.