DOE OSTI2020
FeCoSn2 crystallizes in the monoclinic P2/m space group. The structure is three-dimensional. there are three inequivalent Fe sites. In the first Fe site, Fe is bonded in a distorted q6 geometry to two equivalent Fe, two equivalent Co, and six Sn atoms. Both Fe–Fe bond lengths are 2.58 Å. Both Fe–Co bond lengths are 2.68 Å. There are four shorter (2.65 Å) and two longer (2.68 Å) Fe–Sn bond lengths. In the second Fe site, Fe is bonded in a distorted q6 geometry to four Co and six Sn atoms. There are two shorter (2.58 Å) and two longer (2.66 Å) Fe–Co bond lengths. There are four shorter (2.65 Å) and two longer (2.69 Å) Fe–Sn bond lengths. In the third Fe site, Fe is bonded in a distorted q6 geometry to two equivalent Fe, two equivalent Co, and six Sn atoms. Both Fe–Co bond lengths are 2.68 Å. There are four shorter (2.65 Å) and two longer (2.68 Å) Fe–Sn bond lengths. There are two inequivalent Co sites. In the first Co site, Co is bonded in a 10-coordinate geometry to three Fe, one Co, and six Sn atoms. The Co–Co bond length is 2.69 Å. There are a spread of Co–Sn bond distances ranging from 2.58–2.65 Å. In the second Co site, Co is bonded in a 10-coordinate geometry to two equivalent Fe, two equivalent Co, and six Sn atoms. There are four shorter (2.65 Å) and two longer (2.66 Å) Co–Sn bond lengths. There are three inequivalent Sn sites. In the first Sn site, Sn is bonded in a 9-coordinate geometry to two equivalent Fe and four Co atoms. In the second Sn site, Sn is bonded in a 6-coordinate geometry to four Fe and two equivalent Co atoms. In the third Sn site, Sn is bonded in a hexagonal planar geometry to three Fe and three Co atoms.