DOE OSTI2020
CeCoAl crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are two inequivalent Ce sites. In the first Ce site, Ce is bonded in a 12-coordinate geometry to three equivalent Ce, five Co, and seven Al atoms. There are two shorter (3.24 Å) and one longer (3.27 Å) Ce–Ce bond lengths. There are a spread of Ce–Co bond distances ranging from 2.81–3.24 Å. There are a spread of Ce–Al bond distances ranging from 3.11–3.23 Å. In the second Ce site, Ce is bonded in a 10-coordinate geometry to four Ce, seven Co, and five Al atoms. The Ce–Ce bond length is 2.78 Å. There are a spread of Ce–Co bond distances ranging from 2.98–3.14 Å. There are a spread of Ce–Al bond distances ranging from 3.07–3.20 Å. There are three inequivalent Co sites. In the first Co site, Co is bonded to six Ce and six Al atoms to form CoCe6Al6 cuboctahedra that share corners with four equivalent AlCe6Al2Co4 cuboctahedra, corners with fourteen CoCe6Al6 cuboctahedra, edges with six CoCe6Al6 cuboctahedra, faces with four equivalent CoCe6Al2Co4 cuboctahedra, and faces with fourteen AlCe6Al2Co4 cuboctahedra. There are a spread of Co–Al bond distances ranging from 2.65–2.71 Å. In the second Co site, Co is bonded to six Ce, four Co, and two equivalent Al atoms to form distorted CoCe6Al2Co4 cuboctahedra that share corners with eight CoCe6Al6 cuboctahedra, corners with ten AlCe6Al2Co4 cuboctahedra, edges with two equivalent CoCe6Al2Co4 cuboctahedra, edges with four equivalent AlCe6Al4Co2 cuboctahedra, faces with eight AlCe6Al2Co4 cuboctahedra, and faces with ten CoCe6Al6 cuboctahedra. There are a spread of Co–Co bond distances ranging from 2.68–2.72 Å. Both Co–Al bond lengths are 2.51 Å. In the third Co site, Co is bonded to six Ce, four equivalent Co, and two equivalent Al atoms to form distorted CoCe6Al2Co4 cuboctahedra that share corners with six CoCe6Al6 cuboctahedra, corners with twelve AlCe6Al2Co4 cuboctahedra, edges with six CoCe6Al6 cuboctahedra, faces with eight equivalent CoCe6Al2Co4 cuboctahedra, and faces with ten AlCe6Al2Co4 cuboctahedra. Both Co–Al bond lengths are 2.50 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded to six Ce, four Co, and two equivalent Al atoms to form distorted AlCe6Al2Co4 cuboctahedra that share corners with four equivalent AlCe6Al4Co2 cuboctahedra, corners with eight CoCe6Al6 cuboctahedra, edges with six equivalent AlCe6Al2Co4 cuboctahedra, faces with eight AlCe6Al2Co4 cuboctahedra, and faces with twelve CoCe6Al6 cuboctahedra. Both Al–Al bond lengths are 2.71 Å. In the second Al site, Al is bonded to six Ce, two equivalent Co, and four Al atoms to form distorted AlCe6Al4Co2 cuboctahedra that share corners with eight AlCe6Al2Co4 cuboctahedra, corners with ten CoCe6Al2Co4 cuboctahedra, edges with two equivalent AlCe6Al4Co2 cuboctahedra, edges with four equivalent CoCe6Al2Co4 cuboctahedra, faces with eight CoCe6Al6 cuboctahedra, and faces with ten AlCe6Al2Co4 cuboctahedra. There are one shorter (2.66 Å) and one longer (2.74 Å) Al–Al bond lengths.