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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on K9Fe2Se7 by Materials Project

K9Fe2Se7 crystallizes in the cubic P2_13 space group. The structure is three-dimensional. there are five inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to five Se2- atoms to form distorted KSe5 trigonal bipyramids that share a cornercorner with one KSe6 octahedra, a cornercorner with one FeSe4 tetrahedra, corners with six equivalent KSe5 trigonal bipyramids, an edgeedge with one FeSe4 tetrahedra, and a faceface with one KSe6 octahedra. The corner-sharing octahedral tilt angles are 38°. There are a spread of K–Se bond distances ranging from 3.19–3.43 Å. In the second K1+ site, K1+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are three shorter (3.36 Å) and three longer (3.53 Å) K–Se bond lengths. In the third K1+ site, K1+ is bonded in a 5-coordinate geometry to five Se2- atoms. There are a spread of K–Se bond distances ranging from 3.45–3.57 Å. In the fourth K1+ site, K1+ is bonded in a distorted T-shaped geometry to three equivalent Se2- atoms. All K–Se bond lengths are 3.31 Å. In the fifth K1+ site, K1+ is bonded to six Se2- atoms to form distorted KSe6 octahedra that share corners with three equivalent FeSe4 tetrahedra, corners with three equivalent KSe5 trigonal bipyramids, and faces with three equivalent KSe5 trigonal bipyramids. There are three shorter (3.35 Å) and three longer (3.55 Å) K–Se bond lengths. There are two inequivalent Fe+2.50+ sites. In the first Fe+2.50+ site, Fe+2.50+ is bonded in a trigonal planar geometry to three equivalent Se2- atoms. All Fe–Se bond lengths are 2.36 Å. In the second Fe+2.50+ site, Fe+2.50+ is bonded to four Se2- atoms to form FeSe4 tetrahedra that share corners with three equivalent KSe6 octahedra, corners with three equivalent KSe5 trigonal bipyramids, and edges with three equivalent KSe5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 45°. There are three shorter (2.43 Å) and one longer (2.49 Å) Fe–Se bond lengths. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 7-coordinate geometry to six K1+ and one Fe+2.50+ atom. In the second Se2- site, Se2- is bonded in a 1-coordinate geometry to seven K1+ and one Fe+2.50+ atom. In the third Se2- site, Se2- is bonded in a 1-coordinate geometry to six K1+ and one Fe+2.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3FeSe3 by Materials Project

K3FeSe3 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are three inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of K–Se bond distances ranging from 3.30–3.88 Å. In the second K1+ site, K1+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are a spread of K–Se bond distances ranging from 3.26–3.88 Å. In the third K1+ site, K1+ is bonded in a 4-coordinate geometry to five Se2- atoms. There are a spread of K–Se bond distances ranging from 3.23–3.66 Å. Fe3+ is bonded to four Se2- atoms to form edge-sharing FeSe4 tetrahedra. There are a spread of Fe–Se bond distances ranging from 2.39–2.42 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 6-coordinate geometry to four K1+ and two equivalent Fe3+ atoms. In the second Se2- site, Se2- is bonded in a 1-coordinate geometry to seven K1+ and one Fe3+ atom. In the third Se2- site, Se2- is bonded in a 1-coordinate geometry to seven K1+ and one Fe3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3(FeSe2)2 by Materials Project

K3(FeSe2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six Se2- atoms to form KSe6 octahedra that share corners with eight equivalent FeSe4 tetrahedra, edges with two equivalent FeSe4 tetrahedra, and faces with two equivalent KSe6 octahedra. There are a spread of K–Se bond distances ranging from 3.26–3.41 Å. In the second K1+ site, K1+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of K–Se bond distances ranging from 3.26–3.95 Å. Fe+2.50+ is bonded to four Se2- atoms to form FeSe4 tetrahedra that share corners with four equivalent KSe6 octahedra, an edgeedge with one KSe6 octahedra, and edges with two equivalent FeSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 20–62°. There are a spread of Fe–Se bond distances ranging from 2.40–2.46 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 6-coordinate geometry to four equivalent K1+ and two equivalent Fe+2.50+ atoms. In the second Se2- site, Se2- is bonded in a 7-coordinate geometry to five K1+ and two equivalent Fe+2.50+ atoms. In the third Se2- site, Se2- is bonded in a 6-coordinate geometry to six K1+ and two equivalent Fe+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KFeSe2 by Materials Project

KFeSe2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. K1+ is bonded to eight equivalent Se2- atoms to form distorted KSe8 hexagonal bipyramids that share corners with four equivalent KSe8 hexagonal bipyramids, corners with six equivalent FeSe4 tetrahedra, edges with six equivalent KSe8 hexagonal bipyramids, edges with five equivalent FeSe4 tetrahedra, and faces with two equivalent KSe8 hexagonal bipyramids. There are a spread of K–Se bond distances ranging from 3.49–3.59 Å. Fe3+ is bonded to four equivalent Se2- atoms to form FeSe4 tetrahedra that share corners with six equivalent KSe8 hexagonal bipyramids, edges with five equivalent KSe8 hexagonal bipyramids, and edges with two equivalent FeSe4 tetrahedra. There are two shorter (2.33 Å) and two longer (2.35 Å) Fe–Se bond lengths. Se2- is bonded in a 6-coordinate geometry to four equivalent K1+ and two equivalent Fe3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2(FeSe)5 by Materials Project

K2(FeSe)5 crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. K is bonded in a distorted body-centered cubic geometry to eight Se atoms. There are a spread of K–Se bond distances ranging from 3.32–3.53 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to four Se atoms to form a mixture of distorted corner and edge-sharing FeSe4 tetrahedra. There are a spread of Fe–Se bond distances ranging from 2.47–2.49 Å. In the second Fe site, Fe is bonded to four equivalent Se atoms to form a mixture of distorted corner and edge-sharing FeSe4 tetrahedra. All Fe–Se bond lengths are 2.46 Å. There are two inequivalent Se sites. In the first Se site, Se is bonded in a 7-coordinate geometry to three equivalent K and four Fe atoms. In the second Se site, Se is bonded in a 8-coordinate geometry to four equivalent K and four equivalent Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KFe2Se3 by Materials Project

KFe2Se3 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. K1+ is bonded in a 10-coordinate geometry to ten Se2- atoms. There are a spread of K–Se bond distances ranging from 3.39–3.75 Å. Fe+2.50+ is bonded to four Se2- atoms to form a mixture of edge and corner-sharing FeSe4 tetrahedra. There are two shorter (2.25 Å) and two longer (2.31 Å) Fe–Se bond lengths. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 6-coordinate geometry to two equivalent K1+ and four equivalent Fe+2.50+ atoms. In the second Se2- site, Se2- is bonded in a 2-coordinate geometry to four equivalent K1+ and two equivalent Fe+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K(FeSe)2 by Materials Project

KFe2Se2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. K is bonded in a body-centered cubic geometry to eight equivalent Se atoms. All K–Se bond lengths are 3.40 Å. Fe is bonded to four equivalent Se atoms to form a mixture of distorted edge and corner-sharing FeSe4 tetrahedra. All Fe–Se bond lengths are 2.49 Å. Se is bonded in a 8-coordinate geometry to four equivalent K and four equivalent Fe atoms.

36 MATERIALS SCIENCE↗