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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on KTa(CuSe2)2 by Materials Project

KCu2TaSe4 crystallizes in the orthorhombic Ama2 space group. The structure is three-dimensional. K1+ is bonded in a 9-coordinate geometry to nine Se2- atoms. There are a spread of K–Se bond distances ranging from 3.46–3.94 Å. Ta5+ is bonded to four Se2- atoms to form TaSe4 tetrahedra that share edges with four CuSe4 tetrahedra. There are a spread of Ta–Se bond distances ranging from 2.42–2.47 Å. There are two inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded to four Se2- atoms to form CuSe4 tetrahedra that share corners with four equivalent CuSe4 tetrahedra and edges with two equivalent TaSe4 tetrahedra. There are three shorter (2.46 Å) and one longer (2.47 Å) Cu–Se bond lengths. In the second Cu1+ site, Cu1+ is bonded to four Se2- atoms to form CuSe4 tetrahedra that share corners with six CuSe4 tetrahedra and edges with two equivalent TaSe4 tetrahedra. There are two shorter (2.45 Å) and two longer (2.47 Å) Cu–Se bond lengths. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to one K1+, one Ta5+, and three Cu1+ atoms. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to four equivalent K1+, one Ta5+, and one Cu1+ atom. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to two equivalent K1+, one Ta5+, and two Cu1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2TaCuSe4 by Materials Project

K2TaCuSe4 crystallizes in the orthorhombic Fddd 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 two equivalent TaSe4 tetrahedra, corners with four equivalent CuSe4 tetrahedra, edges with six equivalent KSe8 hexagonal bipyramids, edges with two equivalent CuSe4 tetrahedra, edges with three equivalent TaSe4 tetrahedra, and faces with two equivalent KSe8 hexagonal bipyramids. There are a spread of K–Se bond distances ranging from 3.52–3.72 Å. Ta5+ is bonded to four equivalent Se2- atoms to form TaSe4 tetrahedra that share corners with four equivalent KSe8 hexagonal bipyramids, edges with six equivalent KSe8 hexagonal bipyramids, and edges with two equivalent CuSe4 tetrahedra. All Ta–Se bond lengths are 2.43 Å. Cu1+ is bonded to four equivalent Se2- atoms to form CuSe4 tetrahedra that share corners with eight equivalent KSe8 hexagonal bipyramids, edges with four equivalent KSe8 hexagonal bipyramids, and edges with two equivalent TaSe4 tetrahedra. All Cu–Se bond lengths are 2.47 Å. Se2- is bonded in a 6-coordinate geometry to four equivalent K1+, one Ta5+, and one Cu1+ atom.

36 MATERIALS SCIENCE↗