Materials Data on KNb(CuSe2)2 by Materials Project
KCu2NbSe4 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 3.45–3.93 Å. Nb5+ is bonded to four Se2- atoms to form NbSe4 tetrahedra that share edges with four CuSe4 tetrahedra. There are a spread of Nb–Se bond distances ranging from 2.43–2.48 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 NbSe4 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 NbSe4 tetrahedra. There are two shorter (2.45 Å) and two longer (2.46 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 Nb5+, and three Cu1+ atoms. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to two equivalent K1+, one Nb5+, and two Cu1+ atoms. In the third Se2- site, Se2- is bonded in a 6-coordinate geometry to four equivalent K1+, one Nb5+, and one Cu1+ atom.