Materials Data on K2Cd3Se4 by Materials Project
K2Cd3Se4 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 distorted KSe6 octahedra that share corners with ten CdSe4 tetrahedra, edges with six KSe6 octahedra, and edges with four CdSe4 tetrahedra. There are a spread of K–Se bond distances ranging from 3.35–3.57 Å. In the second K1+ site, K1+ is bonded to six Se2- atoms to form distorted KSe6 octahedra that share corners with twelve CdSe4 tetrahedra, edges with six KSe6 octahedra, and edges with three CdSe4 tetrahedra. There are a spread of K–Se bond distances ranging from 3.47–3.58 Å. There are two inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded to four Se2- atoms to form CdSe4 tetrahedra that share corners with six KSe6 octahedra, corners with four equivalent CdSe4 tetrahedra, edges with three KSe6 octahedra, and edges with two equivalent CdSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 13–95°. There are a spread of Cd–Se bond distances ranging from 2.64–2.79 Å. In the second Cd2+ site, Cd2+ is bonded to four Se2- atoms to form CdSe4 tetrahedra that share corners with eight KSe6 octahedra, corners with four CdSe4 tetrahedra, edges with two KSe6 octahedra, and edges with two CdSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 10–95°. There are a spread of Cd–Se bond distances ranging from 2.65–2.81 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 6-coordinate geometry to three K1+ and three Cd2+ atoms. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to three K1+ and three Cd2+ atoms. In the third Se2- site, Se2- is bonded to three K1+ and three Cd2+ atoms to form a mixture of distorted edge and corner-sharing SeK3Cd3 octahedra. The corner-sharing octahedra tilt angles range from 0–55°.