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DOE OSTI2020

Materials Data on Sm2Fe17C3 by Materials Project

Sm2Fe17C3 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Sm is bonded in a distorted trigonal planar geometry to four Fe and three equivalent C atoms. There are one shorter (3.11 Å) and three longer (3.35 Å) Sm–Fe bond lengths. All Sm–C bond lengths are 2.51 Å. There are four inequivalent Fe sites. In the first Fe site, Fe is bonded to two equivalent Sm and ten Fe atoms to form distorted FeSm2Fe10 cuboctahedra that share corners with four equivalent FeSm2Fe10 cuboctahedra, corners with two equivalent CSm2Fe4 octahedra, faces with four equivalent FeSm2Fe10 cuboctahedra, and faces with four equivalent CSm2Fe4 octahedra. The corner-sharing octahedral tilt angles are 44°. There are a spread of Fe–Fe bond distances ranging from 2.45–2.67 Å. In the second Fe site, Fe is bonded in a single-bond geometry to four Fe and one C atom. Both Fe–Fe bond lengths are 2.74 Å. The Fe–C bond length is 1.88 Å. In the third Fe site, Fe is bonded in a single-bond geometry to three Fe and one C atom. The Fe–Fe bond length is 2.66 Å. The Fe–C bond length is 1.91 Å. In the fourth Fe site, Fe is bonded in a 2-coordinate geometry to one Sm and thirteen Fe atoms. The Fe–Fe bond length is 2.37 Å. C is bonded to two equivalent Sm and four Fe atoms to form CSm2Fe4 octahedra that share corners with two equivalent FeSm2Fe10 cuboctahedra, corners with four equivalent CSm2Fe4 octahedra, and faces with four equivalent FeSm2Fe10 cuboctahedra. The corner-sharing octahedral tilt angles are 60°.

36 MATERIALS SCIENCE↗

DOE OSTI2026

Chemical bond and phase stability of Ga-doped Sm2Fe17Cx magnet

Sm2Fe17C3 phase (2:17) is metastable and exhibits excellent intrinsic hard magnetic properties. Doping elements such as Ga facilitate the formation of a single-phase 2:17 structure in arc-melted Sm2Fe17Cx alloys, which opens a promising route for fabricating fully dense bulk Sm2Fe17Cx magnets via high-temperature techniques such as melting and sintering. First-principles electronic structure calculation indicates that Ga prefers to partially replace Fe at the 9d and 18h crystallographic sites in Sm2Fe17C3 and Sm2Fe17, respectively. This difference in site preference is attributed to the distinct chemical environments surrounding the Fe atoms in the two compounds. Ga substitution favors the Sm–Ga bonding formation while avoiding Ga–C interactions. Doped Ga atoms result in more negative formation energy in Sm2(Fe, Ga)17C3, indicating improved structural stability. Crystal Orbital Hamilton Population analysis reveals that carbon insertion weakens the bonding of Sm-Fe (18h) and Sm-Fe (18f) in Sm2Fe17C3. Ga doping facilitates electron redistribution across chemical bonds, thereby reinforcing Fe(18h)–Sm and Fe(18f)–Sm interactions and stabilizing the carbon-centered octahedral local structure. This synergistic effect contributes significantly to the observed enhancement in phase stability of Sm2(Fe, Ga)17Cx. These findings suggest that chemical bond engineering through the selective doping of Ga can enhance phase stability and facilitate the synthesis of Sm2Fe17C3, providing a viable strategy for developing advanced magnets.

Liu, Xubo [Critical Materials Innovation Hub, Divi↗