DOE OSTI2020
Mo15Cd2Se19 crystallizes in the trigonal R-3c space group. The structure is three-dimensional. there are three inequivalent Mo+2.27+ sites. In the first Mo+2.27+ site, Mo+2.27+ is bonded in a see-saw-like geometry to four Se2- atoms. There are two shorter (2.56 Å) and two longer (2.60 Å) Mo–Se bond lengths. In the second Mo+2.27+ site, Mo+2.27+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share corners with three equivalent MoSe5 square pyramids, corners with two equivalent CdSe5 trigonal bipyramids, and edges with five MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.56–2.64 Å. In the third Mo+2.27+ site, Mo+2.27+ is bonded to five Se2- atoms to form MoSe5 square pyramids that share corners with four MoSe5 square pyramids, corners with three equivalent CdSe5 trigonal bipyramids, and edges with three MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.55–2.73 Å. Cd2+ is bonded to five Se2- atoms to form distorted CdSe5 trigonal bipyramids that share corners with fifteen MoSe5 square pyramids. There are a spread of Cd–Se bond distances ranging from 3.16–3.57 Å. There are five inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 10-coordinate geometry to three equivalent Mo+2.27+ and one Cd2+ atom. In the second Se2- site, Se2- is bonded in a 4-coordinate geometry to four Mo+2.27+ atoms. In the third Se2- site, Se2- is bonded in a 7-coordinate geometry to three equivalent Mo+2.27+ and one Cd2+ atom. In the fourth Se2- site, Se2- is bonded in a 5-coordinate geometry to four Mo+2.27+ and one Cd2+ atom. In the fifth Se2- site, Se2- is bonded in a 4-coordinate geometry to four Mo+2.27+ atoms.