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.