Materials Data on BaCu2GeSe4 by Materials Project

BaCu2GeSe4 crystallizes in the trigonal P3_1 space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Ba–Se bond distances ranging from 3.35–3.42 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 corners with four equivalent GeSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.45–2.52 Å. In the second Cu1+ site, Cu1+ is bonded to four Se2- atoms to form CuSe4 tetrahedra that share corners with four equivalent CuSe4 tetrahedra and corners with four equivalent GeSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.45–2.52 Å. Ge4+ is bonded to four Se2- atoms to form GeSe4 tetrahedra that share corners with eight CuSe4 tetrahedra. There are three shorter (2.42 Å) and one longer (2.43 Å) Ge–Se bond lengths. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent Ba2+, two Cu1+, and one Ge4+ atom. In the second Se2- site, Se2- is bonded to two equivalent Ba2+, two Cu1+, and one Ge4+ atom to form a mixture of distorted corner and edge-sharing SeBa2Cu2Ge trigonal bipyramids. In the third Se2- site, Se2- is bonded to two equivalent Ba2+, two Cu1+, and one Ge4+ atom to form a mixture of distorted corner and edge-sharing SeBa2Cu2Ge trigonal bipyramids. In the fourth Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent Ba2+, two Cu1+, and one Ge4+ atom.