DOE OSTI2020
Ce2Fe20Si2C crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Ce is bonded in a distorted single-bond geometry to sixteen Fe and one C atom. There are a spread of Ce–Fe bond distances ranging from 3.07–3.48 Å. The Ce–C bond length is 2.63 Å. There are eleven inequivalent Fe sites. In the first Fe site, Fe is bonded in a 1-coordinate geometry to two equivalent Ce, ten Fe, and two Si atoms. There are a spread of Fe–Fe bond distances ranging from 2.61–2.73 Å. There are one shorter (2.58 Å) and one longer (2.65 Å) Fe–Si bond lengths. In the second Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Ce, nine Fe, and one Si atom. There are a spread of Fe–Fe bond distances ranging from 2.46–2.65 Å. The Fe–Si bond length is 2.41 Å. In the third Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Ce, eight Fe, and two Si atoms. There are a spread of Fe–Fe bond distances ranging from 2.47–2.63 Å. There are one shorter (2.41 Å) and one longer (2.42 Å) Fe–Si bond lengths. In the fourth Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Ce, nine Fe, and one Si atom. There are a spread of Fe–Fe bond distances ranging from 2.43–2.69 Å. The Fe–Si bond length is 2.40 Å. In the fifth Fe site, Fe is bonded to two equivalent Ce and ten Fe atoms to form distorted FeCe2Fe10 cuboctahedra that share corners with three FeCe2Fe10 cuboctahedra, corners with two equivalent CCe2Fe4 octahedra, an edgeedge with one CCe2Fe4 octahedra, and faces with two FeCe2Fe10 cuboctahedra. The corner-sharing octahedra tilt angles range from 28–71°. There are a spread of Fe–Fe bond distances ranging from 2.40–2.65 Å. In the sixth Fe site, Fe is bonded in a single-bond geometry to eight Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.39–2.56 Å. The Fe–C bond length is 1.86 Å. In the seventh Fe site, Fe is bonded in a single-bond geometry to seven Fe, one Si, and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.38–2.59 Å. The Fe–Si bond length is 2.38 Å. The Fe–C bond length is 1.87 Å. In the eighth Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Ce, eight Fe, and two Si atoms. The Fe–Fe bond length is 2.57 Å. There are one shorter (2.39 Å) and one longer (2.41 Å) Fe–Si bond lengths. In the ninth Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Ce, nine Fe, and one Si atom. The Fe–Fe bond length is 2.39 Å. The Fe–Si bond length is 2.39 Å. In the tenth Fe site, Fe is bonded to two equivalent Ce and ten Fe atoms to form distorted FeCe2Fe10 cuboctahedra that share corners with two equivalent FeCe2Fe10 cuboctahedra, faces with two equivalent FeCe2Fe10 cuboctahedra, and faces with two equivalent CCe2Fe4 octahedra. In the eleventh Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Ce and ten Fe atoms. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 10-coordinate geometry to ten Fe atoms. In the second Si site, Si is bonded in a 10-coordinate geometry to ten Fe atoms. C is bonded to two equivalent Ce and four Fe atoms to form CCe2Fe4 octahedra that share corners with four equivalent FeCe2Fe10 cuboctahedra, edges with two equivalent FeCe2Fe10 cuboctahedra, and faces with two equivalent FeCe2Fe10 cuboctahedra.