DOE OSTI2020
CeMg2Cu9 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Mg is bonded in a 12-coordinate geometry to twelve Cu atoms. There are a spread of Mg–Cu bond distances ranging from 2.88–2.96 Å. Ce is bonded in a distorted hexagonal planar geometry to eighteen Cu atoms. There are six shorter (2.91 Å) and twelve longer (3.25 Å) Ce–Cu bond lengths. There are four inequivalent Cu sites. In the first Cu site, Cu is bonded to six equivalent Mg and six equivalent Cu atoms to form CuMg6Cu6 cuboctahedra that share corners with twelve equivalent CuCe2Mg3Cu7 cuboctahedra, edges with six equivalent CuMg6Cu6 cuboctahedra, and faces with eighteen equivalent CuCe2Mg3Cu7 cuboctahedra. All Cu–Cu bond lengths are 2.46 Å. In the second Cu site, Cu is bonded in a 12-coordinate geometry to three equivalent Ce and nine Cu atoms. There are six shorter (2.53 Å) and three longer (2.91 Å) Cu–Cu bond lengths. In the third Cu site, Cu is bonded in a 12-coordinate geometry to three equivalent Ce and nine Cu atoms. All Cu–Cu bond lengths are 2.51 Å. In the fourth Cu site, Cu is bonded to three equivalent Mg, two equivalent Ce, and seven Cu atoms to form CuCe2Mg3Cu7 cuboctahedra that share corners with seventeen CuCe2Mg3Cu7 cuboctahedra, edges with eight equivalent CuCe2Mg3Cu7 cuboctahedra, and faces with fourteen CuMg6Cu6 cuboctahedra. There are two shorter (2.50 Å) and two longer (2.54 Å) Cu–Cu bond lengths.