DOE OSTI2020
Eu2Cu6P5 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Eu3+ is bonded to eight P3- atoms to form EuP8 hexagonal bipyramids that share corners with sixteen CuP4 tetrahedra, edges with four equivalent EuP8 hexagonal bipyramids, edges with eight CuP4 tetrahedra, and faces with four equivalent EuP8 hexagonal bipyramids. There are four shorter (3.06 Å) and four longer (3.11 Å) Eu–P bond lengths. There are two inequivalent Cu+1.50+ sites. In the first Cu+1.50+ site, Cu+1.50+ is bonded to four P3- atoms to form CuP4 tetrahedra that share corners with four equivalent EuP8 hexagonal bipyramids, corners with ten equivalent CuP4 tetrahedra, edges with two equivalent EuP8 hexagonal bipyramids, and edges with five equivalent CuP4 tetrahedra. All Cu–P bond lengths are 2.41 Å. In the second Cu+1.50+ site, Cu+1.50+ is bonded to four equivalent P3- atoms to form CuP4 tetrahedra that share corners with eight equivalent EuP8 hexagonal bipyramids, corners with four equivalent CuP4 tetrahedra, edges with four equivalent EuP8 hexagonal bipyramids, and edges with four equivalent CuP4 tetrahedra. All Cu–P bond lengths are 2.40 Å. There are three inequivalent P3- sites. In the first P3- site, P3- is bonded in a body-centered cubic geometry to eight equivalent Cu+1.50+ atoms. In the second P3- site, P3- is bonded in a 9-coordinate geometry to four equivalent Eu3+, four equivalent Cu+1.50+, and one P3- atom. The P–P bond length is 2.29 Å. In the third P3- site, P3- is bonded in a 9-coordinate geometry to four equivalent Eu3+, four equivalent Cu+1.50+, and one P3- atom.