Materials Data on KFeSeS by Materials Project
KFeSeS crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to four equivalent Se2- and four equivalent S2- atoms to form distorted KSe4S4 hexagonal bipyramids that share corners with four equivalent KSe4S4 hexagonal bipyramids, corners with six FeSe2S2 tetrahedra, edges with six KSe4S4 hexagonal bipyramids, edges with five FeSe2S2 tetrahedra, and faces with two equivalent KSe4S4 hexagonal bipyramids. There are two shorter (3.38 Å) and two longer (3.43 Å) K–Se bond lengths. There are two shorter (3.44 Å) and two longer (3.61 Å) K–S bond lengths. In the second K1+ site, K1+ is bonded to four equivalent Se2- and four equivalent S2- atoms to form distorted KSe4S4 hexagonal bipyramids that share corners with four equivalent KSe4S4 hexagonal bipyramids, corners with six FeSe2S2 tetrahedra, edges with six KSe4S4 hexagonal bipyramids, edges with five FeSe2S2 tetrahedra, and faces with two equivalent KSe4S4 hexagonal bipyramids. There are two shorter (3.49 Å) and two longer (3.53 Å) K–Se bond lengths. There are two shorter (3.46 Å) and two longer (3.51 Å) K–S bond lengths. There are two inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to two equivalent Se2- and two equivalent S2- atoms to form FeSe2S2 tetrahedra that share corners with six KSe4S4 hexagonal bipyramids, edges with five KSe4S4 hexagonal bipyramids, and edges with two equivalent FeSe2S2 tetrahedra. Both Fe–Se bond lengths are 2.33 Å. Both Fe–S bond lengths are 2.19 Å. In the second Fe3+ site, Fe3+ is bonded to two equivalent Se2- and two equivalent S2- atoms to form FeSe2S2 tetrahedra that share corners with six KSe4S4 hexagonal bipyramids, edges with five KSe4S4 hexagonal bipyramids, and edges with two equivalent FeSe2S2 tetrahedra. Both Fe–Se bond lengths are 2.34 Å. Both Fe–S bond lengths are 2.18 Å. Se2- is bonded in a 6-coordinate geometry to four K1+ and two Fe3+ atoms. S2- is bonded in a 2-coordinate geometry to four K1+ and two Fe3+ atoms.