DOE OSTI2020
TbFe6Ge6 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Tb is bonded to twelve Fe and eight Ge atoms to form distorted TbFe12Ge8 hexagonal bipyramids that share corners with four equivalent TbFe12Ge8 hexagonal bipyramids, faces with eight equivalent FeTb2Fe4Ge6 cuboctahedra, and faces with four equivalent TbFe12Ge8 hexagonal bipyramids. There are a spread of Tb–Fe bond distances ranging from 3.25–3.30 Å. There are a spread of Tb–Ge bond distances ranging from 2.84–3.00 Å. There are three inequivalent Fe sites. In the first Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Tb, four Fe, and six Ge atoms. All Fe–Fe bond lengths are 2.56 Å. There are a spread of Fe–Ge bond distances ranging from 2.48–2.68 Å. In the second Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Tb, four Fe, and six Ge atoms. Both Fe–Fe bond lengths are 2.57 Å. There are four shorter (2.52 Å) and two longer (2.67 Å) Fe–Ge bond lengths. In the third Fe site, Fe is bonded to two equivalent Tb, four Fe, and six Ge atoms to form distorted FeTb2Fe4Ge6 cuboctahedra that share corners with four equivalent FeTb2Fe4Ge6 cuboctahedra, edges with two equivalent FeTb2Fe4Ge6 cuboctahedra, faces with four equivalent FeTb2Fe4Ge6 cuboctahedra, and faces with four equivalent TbFe12Ge8 hexagonal bipyramids. Both Fe–Fe bond lengths are 2.57 Å. There are a spread of Fe–Ge bond distances ranging from 2.51–2.69 Å. There are five inequivalent Ge sites. In the first Ge site, Ge is bonded in a 8-coordinate geometry to two equivalent Tb and six Fe atoms. In the second Ge site, Ge is bonded in a 6-coordinate geometry to six Fe atoms. In the third Ge site, Ge is bonded in a 9-coordinate geometry to three equivalent Tb and six Fe atoms. In the fourth Ge site, Ge is bonded in a 8-coordinate geometry to one Tb, six Fe, and one Ge atom. The Ge–Ge bond length is 2.50 Å. In the fifth Ge site, Ge is bonded in a 7-coordinate geometry to one Tb and six Fe atoms.