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All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Correlation of Spectral and Electrochemical Properties of a Series of Ferrocene Derivatives

Charge-transfer-to-solvent (CTTS) bands are observed in the UV/VIS spectra of a series of ferrocene derivatives (ferrocene; 1,1’-dimethyl; 1,2,3,4,5-pentamethyl; 1,2,3,4,l’,2’,3’,4’-octamethyl; and decamethyl) by the addition of increasing amounts of CCl4 to ethanol solutions. A linear correlation (slope = 8540 per cm/V) was found between the redox potential and the energy of the CTTS band, consistent with electrochemical and photochemical oxidation by removal of an electron from the same molecular orbital. Inclusion of literature data for ruthenocene and [(η^(5)-C5H5)Fe(CO)]4 results in a line with a slope of 8140 per cm/V, within 1 percent of the wavenumber to electron volt conversion factor. Calculation of association constants (K) shows a slight decrease (1.2 to 0.7 per mole fraction) as the bulkiness of the cyclopentadienyl ring increases, consistent with either a steric or a repulsive electronic effect. The extinction coefficient of the CTTS absorption was constant at approximately 1700 per Mcm .

ultraviolet spectroscopy↗
DOE OSTI2021

Understanding the Reactivity and Decomposition of a Highly Active Iron Pincer Catalyst for Hydrogenation and Dehydrogenation Reactions

The iron pincer complex ( iPr PNP)Fe(H)(CO) (1, iPr PNP – = N(CH 2 CH 2 PiPr 2 ) 2 - ) is an active (pre)catalyst for many hydrogenation and dehydrogenation reactions. This is in part because 1 can reversibly add H 2 across the iron-amide bond to form ( iPr PN H P)Fe(H) 2 (CO) (2, iPr PN H P = HN(CH 2 CH 2 P i Pr 2 ) 2 ). However, rapid decomposition limits the catalytic performance of 1 and related complexes. We explored the pathways through which catalytic intermediates related to 1 and 2 undergo decomposition. This involved characterizing the unstable and previously unobserved complexes [( iPr PN H P)Fe(H)(CO)(L)] + (5-L; L = THF or N 2 ) and [( iPr PN H P)Fe(H)(H 2 )(CO)] + (8), which are proposed as intermediates when 1 and 2 are used as catalysts. Compound 8 was synthesized through the reaction of ( iPr PN H P)Fe(H)(CO)(PF 6 ) (6) with H 2 , and the solid-state structure was established using both X-ray and neutron diffraction. As part of our studies on understanding the reactivity of 5-L, we determined the thermodynamic hydricity of 2, which is valuable for predicting its reactivity as a hydride donor. Further, it is shown that species such as 5-L decompose to the same inactive species observed in catalysis using 1 and 2, and theoretical calculations suggest that this likely occurs via a bimolecular pathway. To provide support for this hypothesis, we isolated the dimeric species [{( iPr PN H P)Fe(H)(CO)} 2 {μ-CN}] + (11) and [{( iPr PN H P)Fe(H)(CO)} 2 {μ-OC(H)O}] + (12), which show that catalytic intermediates ligated by iPr PN H P can form dimeric species. Our results provide general strategies for improving catalysis using 1 and 2, and we used this information to rationally increase the performance of 1 in formic acid dehydrogenation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Understanding the deformation behavior of the γ rich transformative Fe 38.5 Mn 20 Co 20 Cr 15 Si 5 Cu 1.5 complex concentrated alloy using in situ synchrotron diffraction

In situ tensile testing coupled with synchrotron x-ray diffraction was used to study the deformation behavior of metastability-engineered Fe 38.5 Mn 20 Co 20 Cr 15 Si 5 Cu 1.5 complex concentrated alloy. Monitoring the evolution of phase fraction and strain hardening response allowed the determination of true critical stress for the onset of the transformation-induced plasticity (TRIP) to be ∼375 MPa, preceded by slip starting at ∼255 MPa. In situ EBSD was used to validate the critical stress for transformation at the microstructure level and observe slip traces to confirm prior slip activity before the transformation. Further, a modeling framework based on stacking fault energy (SFE) was developed to predict the critical stress for transformation. Modeling suggested the SFE of the alloy to fall nearly 15 mJ/m 2 , which agrees well with SFE values calculated using synchrotron peak shifting (12 mJ/m 2 ) and thermodynamic calculation (11 mJ/m 2 ). As a result of γ-fcc to ε-hcp phase transformation, new {0002} ε planes emerged parallel to unaligned {111} γ planes with the tensile loading following S-N orientation relationship. Such selective emergence of new diffraction rings corresponding to ε phase is understood based on the reorientation of γ crystals with reference to tensile axis. In conclusion, this approach can be extended to effectively design alloys based on critical stress required for activating different deformation mechanisms to further push the limits of the strength-ductility envelope.

Complex concentrated alloy↗
DOE OSTI2020

Materials Data on FeCoGe by Materials Project

CoFeGe crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Fe is bonded in a 5-coordinate geometry to six equivalent Co and five equivalent Ge atoms. All Fe–Co bond lengths are 2.66 Å. There are three shorter (2.35 Å) and two longer (2.49 Å) Fe–Ge bond lengths. Co is bonded in a 6-coordinate geometry to six equivalent Fe, two equivalent Co, and six equivalent Ge atoms. Both Co–Co bond lengths are 2.49 Å. All Co–Ge bond lengths are 2.66 Å. Ge is bonded in a 5-coordinate geometry to five equivalent Fe and six equivalent Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Oxygen Deficiency and Migration-Mediated Electric Polarization in Magnetic Fe,Co-Substituted SrTiO3−δ

We use density functional theory (DFT) calculations to show that oxygen vacancies (vO) and mobility induce noncentrosymmetric polar structures in SrTi1−x−yFexCoyO3−δ (STFC, x=y=0.125) with δ={0.125,0.25}, enhance the saturation magnetization, and give rise to large changes in the electric polarization |ΔP|. We present an intuitive set of rules to describe the properties of STFC, which are based on the interplay between (Co/Fe)-vO defects, magnetic cation coordination, and topological vacancy disorder. STFC structures consist of layered crystals with sheets of linearly organized O4,5,6-coordinated Fe–Co pairs, sandwiched with layers of O5-coordinated Ti. (Co/Fe)-vO defects are the source of crystal distortions, cation off-centering and bending of the oxygen octahedra which, considering the charge redistribution mediated by vO and the cations’ electronegativity and valence states, triggers an effective electric polarization. Oxygen migration for δ=0.125 leads to |ΔP|>∼10 µC/cm2 due to quantum-of-polarization differences between δ=0.125 structures. Increasing the oxygen deficiency to δ=0.25 yields |ΔP|, the O migration of which resolved polarization for δ=0.25 is >∼3 µC/cm2. Magnetism is dominated by the Fe,Co spin states for δ=0.125, and there is a contribution from Ti magnetic moments (∼1 μB) for δ=0.25. Magnetic and electric order parameters change for variations of δ or oxygen migration for a given oxygen deficiency. Our results capture characteristics observed in the end members of the series SrTi(Co,Fe)O3, and suggest the existence of a broader set of rules for oxygen-deficient multiferroic oxides.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Surface Regulating of a Double–Perovskite Electrode for Protonic Ceramic Fuel Cells to Enhance Oxygen Reduction Activity and Contaminants Poisoning Tolerance

Protonic ceramic fuel cells (PCFCs) are one of the most efficient energy conversion devices. However, the performance of current PCFCs is greatly limited by the sluggish oxygen reduction reaction (ORR) kinetics and the fast degradation of cathode due to contaminants poisoning (such as Cr species and steam). In this work, we report a surface regulating of a double perovskite PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ (PBSCF) cathode by a Pr 0.9 Fe 0.7 Co 0.3 O 3 (PFC) catalyst coating to enhance the ORR activity and stability. When tested in direct contact with Cr in the air with 3% H 2 O at 650 °C, the polarization resistance (Rp) of the PFC-PBSCF electrode increases from $\approx$0.39 to 0.45 Ω cm 2 after 100 h operation; in contrast, the R p of a PBSCF electrode increases from 0.63 to 0.82 Ω cm 2 . Further, a PCFC with the PFC-PBSCF cathode demonstrates an excellent peak power density ($\approx$1.08 W cm -2 at 650 °C) and significantly enhanced durability (degradation rate of 0.03 % h -1 ), much better than those of the cells with a PBSCF cathode ($\approx$0.75 W cm -2 and degradation rate of 0.12 % h -1 ). Raman spectroscopy and density functional theory calculations indicate that the PFC catalyst coating diminishes the formation of Cr species, such as (Ba 1-x Sr x )CrO 4 , on the cathode surface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Iron Carbonyl Complexes of [2.2.2]Hericene as a Rigid Tris(1,3-diene) Ligand

Hericene is an unusual hexaolefin consisting of three 1,3-diene units located on a rigid bicyclo [2.2.2]octane framework that restricts the geometrical relationships of metal atoms bonded to these olefinic units. In order to explore possible effects of this rigidity limiting metal–metal interaction in polynuclear derivatives possibly stabilizing coordinatively unsaturated species, the structures and energetics of the hericene iron carbonyl complexes (hericene)Fem(CO)n (m = 1, n = 3; m = 2, n = 6, 5; m = 3, n = 9, 8) have been investigated by density functional theory. The lowest-energy (hericene)Fem(CO)3m (m = 1, 2, 3) structures have the cavities of the hericene ligand filled with a single Fe(CO)3 moiety bonded to a 1,3-diolefin unit. Such species have been synthesized by the reaction of Fe2(CO)9 with hericene. For the (hericene)Fe2(CO)5 system, the lowest energy structures are singlet structures with an Fe(CO)3 unit bonded to a 1,3-diene unit in one hericene cavity and an Fe(CO)2 unit in another hericene cavity bonded to three C=C double bonds from two 1,3-diene units. Higher energy (hericene)Fe2(CO)5 structures include a structure in which a single hericene cavity contains a Fe2(CO)4(µ-CO) moiety with each iron atom bonded to a 1,3-diene unit. In addition, both singlet and triplet (hericene)Fe2(CO)5 structures are found in which an Fe(CO)3 moiety and an Fe(CO)2 moiety located in separate hericene cavities are each bonded to a 1,3-diene unit. The lowest-energy (hericene)Fe3(CO)8 structures have two hericene cavities containing Fe(CO)3 moieties fully bonded to 1,3-diene units and a third hericene cavity containing an Fe(CO)2 moiety fully bonded to a 1,3-diene unit.

Luo, Jinfeng↗
DOE OSTI2021

Effect of atom substitutions on the magnetic properties in Ce 2 Fe 17 : Toward permanent magnet applications

Due to the rapidly developing technologies and huge market demand, there has been increasing interest internationally in exploring permanent magnet formulations in addition to the well-known Nd 2 Fe 14 B and SmCo 5 /Sm 2 Co 17 . Given Fe's low materials cost and generally high magnetization, Fe-rich rare earth binaries such as Ce 2 Fe 17 comprise a rich “hunting ground” for such new materials. While this compound suffers from a low ordering point and is a heli magnet, these difficulties are easily remedied by the substitution of appropriate amounts of cobalt for Fe, with room-temperature saturation magnetization as high as 1.5 T. In this work, we try to switch the all-important magnetic anisotropy from planar to uniaxial behavior in Ce 2 Fe 17 via 18 h - and 6 c -type atom substitutions with Si, Ir, and numerous other atoms. The uniaxial magnetocrystalline anisotropy is successfully achieved in the 6 c -site-substituted Ce 2 Fe 15 Ir 2 systems, along with large magnetization. We find that iridium substitution, in particular, induces a substantial uniaxial anisotropy of 11.25 MJ/m 3 , which is comparable to most of the current rare earth permanent magnets. Although the iridium substitution is costly, the finding of Ir-triggered uniaxial magnetic anisotropy indicates the potential of Ce–Fe-based alloys for permanent magnets.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A room temperature polar magnetic metal

The emergence of long-range magnetic order in noncentrosymmetric compounds has stimulated interest in the possibility of exotic spin transport phenomena and topologically protected spin textures for applications in next-generation spintronics. Polar magnets, with broken symmetries of spatial inversion and time reversal, usually host chiral spin textures. This work reports on a wurtzite-structure polar magnetic metal, identified as AA'-stacked (Fe 0.5 Co 0.5 ) 5 GeTe 2 , which exhibits a Néel-type skyrmion lattice as well as a Rashba-Edelstein effect at room temperature. Atomic resolution imaging of the structure reveals a structural transition as a function of Co-substitution, leading to the emergence of the polar phase at 50% Co. We report this discovery reveals an unprecedented layered polar magnetic system for investigating intriguing spin topologies, and it ushers in a promising new framework for spintronics.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Microstructural evolutions, phase transformations and hard magnetic properties in polycrystalline Ce–Co–Fe–Cu alloys

This work focuses on systematic studies of Ce–Co based 1:5 permanent magnet alloys of CeCo 4.4-x Fe x Cu 0.6 and CeCo 3.9-x Fe x Cu 1.2 (x = 0, 0.3, 0.6, 0.9, 1.2, 1.8) by varying Co:Fe. The overarching aim of this manuscript is to elucidate the hard-magnetic properties through a better understanding of phase formation by the structural, microstructural, and magnetic properties in these materials. Improved mutual solubility of Fe in the 1:5 phase has been observed with an extended homogeneity range by Cu substitution. For both composition series, Fe contents of x ≤ 0.6 show a homogeneous microstructure with a single 1:5 phase and good magnetic properties. The composition region 0.6 < x ≤ 0.9 appears to be near the boundary of solubility and evolution of other phases. At x = 1.8, it is found that the homogeneous 1:5 phase and magnetic hardness deteriorated due to the evolution of secondary phases such as 2:17, 2:7, and Fe–Co. Furthermore, the addition of Fe improved both the magnetization and Curie temperature via increased effective exchange interactions, while an increase in Cu content enhanced coercivity.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2024

Benchmarking nitrous oxide adsorption and activation in metal–organic frameworks bearing coordinatively unsaturated metal centers

Anthropogenic emissions of N 2 O, the third most abundant greenhouse gas after CO 2 and CH 4 , are contributing to global climate change. Although metal–organic frameworks (MOFs) have been widely studied as adsorbents for CO 2 and CH 4 , less effort has focused on the use of MOFs to remove N 2 O from emission streams or from air. Further, N 2 O activation would enable its use as an inexpensive oxidant for fine chemical synthesis. Here, in this paper, we identify features that contribute to strong binding and high uptake of N 2 O at coordinatively unsaturated metal sites in the M 2 Cl 2 (btdd) (M = Mn, Co, Ni, Cu; btdd 2– = bis(1,2,3-triazolo[4,5-b],[4',5'-i])dibenzo[1,4]dioxin) and M 2 (dobdc) (M = Mg, Mn, Fe, Co, Ni, Cu, Zn; dobdc 4– = 2,5-dioxido-1,4-benzenedicarboxylate) series of MOFs. Combined experimental and computational studies suggest that N 2 O adsorption at open-metal-sites is primarily based on electrostatic interactions, rather than π-backbonding, causing MOFs with more Lewis acidic metal centers to be superior N 2 O adsorbents. As a result, Mg 2 (dobdc) demonstrates strong binding and record-setting N 2 O uptake (8.75 mmol g –1 at 1 bar and 298 K). Using density functional theory (DFT) to characterize reactive intermediates and transition states, we demonstrate that N 2 O activation to form a M(IV)–oxo species and N 2 is thermodynamically favorable in Mn 2 (dobdc) and Fe 2 (dobdc) but appears to be kinetically limited in Mn 2 (dobdc). Our work lays a foundation for understanding N 2 O adsorption and activation in MOFs, paving the way for the design of promising next-generation materials for N 2 O capture and utilization.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn3FeCo2P3 by Materials Project

Mn3FeCo2P3 crystallizes in the monoclinic Pm space group. The structure is three-dimensional. there are twelve inequivalent Mn sites. In the first Mn site, Mn is bonded in a 5-coordinate geometry to five P atoms. There are a spread of Mn–P bond distances ranging from 2.42–2.53 Å. In the second Mn site, Mn is bonded in a 5-coordinate geometry to two Fe, four Co, and five P atoms. Both Mn–Fe bond lengths are 2.72 Å. There are two shorter (2.66 Å) and two longer (2.69 Å) Mn–Co bond lengths. There are a spread of Mn–P bond distances ranging from 2.43–2.53 Å. In the third Mn site, Mn is bonded in a 5-coordinate geometry to five P atoms. There are a spread of Mn–P bond distances ranging from 2.42–2.53 Å. In the fourth Mn site, Mn is bonded in a 5-coordinate geometry to one Fe, five Co, and five P atoms. The Mn–Fe bond length is 2.71 Å. There are a spread of Mn–Co bond distances ranging from 2.67–2.72 Å. There are a spread of Mn–P bond distances ranging from 2.44–2.52 Å. In the fifth Mn site, Mn is bonded in a 5-coordinate geometry to five P atoms. There are a spread of Mn–P bond distances ranging from 2.42–2.53 Å. In the sixth Mn site, Mn is bonded in a 5-coordinate geometry to five P atoms. There are a spread of Mn–P bond distances ranging from 2.42–2.53 Å. In the seventh Mn site, Mn is bonded in a 5-coordinate geometry to five P atoms. There are a spread of Mn–P bond distances ranging from 2.41–2.51 Å. In the eighth Mn site, Mn is bonded in a 5-coordinate geometry to five P atoms. There are a spread of Mn–P bond distances ranging from 2.41–2.53 Å. In the ninth Mn site, Mn is bonded in a 5-coordinate geometry to five P atoms. There are a spread of Mn–P bond distances ranging from 2.41–2.53 Å. In the tenth Mn site, Mn is bonded in a 5-coordinate geometry to five P atoms. There are a spread of Mn–P bond distances ranging from 2.41–2.51 Å. In the eleventh Mn site, Mn is bonded in a 5-coordinate geometry to five P atoms. There are a spread of Mn–P bond distances ranging from 2.41–2.52 Å. In the twelfth Mn site, Mn is bonded in a 5-coordinate geometry to five P atoms. There are a spread of Mn–P bond distances ranging from 2.41–2.52 Å. There are four inequivalent Fe sites. In the first Fe site, Fe is bonded to one Mn and four P atoms to form distorted corner-sharing FeMnP4 tetrahedra. There are three shorter (2.20 Å) and one longer (2.24 Å) Fe–P bond lengths. In the second Fe site, Fe is bonded to one Mn and four P atoms to form distorted corner-sharing FeMnP4 tetrahedra. There are a spread of Fe–P bond distances ranging from 2.19–2.23 Å. In the third Fe site, Fe is bonded to four P atoms to form distorted corner-sharing FeP4 tetrahedra. There are a spread of Fe–P bond distances ranging from 2.19–2.23 Å. In the fourth Fe site, Fe is bonded to one Mn and four P atoms to form distorted corner-sharing FeMnP4 tetrahedra. There are three shorter (2.20 Å) and one longer (2.24 Å) Fe–P bond lengths. There are eight inequivalent Co sites. In the first Co site, Co is bonded in a 4-coordinate geometry to four P atoms. There are a spread of Co–P bond distances ranging from 2.20–2.24 Å. In the second Co site, Co is bonded in a 4-coordinate geometry to one Mn and four P atoms. There are a spread of Co–P bond distances ranging from 2.20–2.24 Å. In the third Co site, Co is bonded in a 4-coordinate geometry to two equivalent Mn and four P atoms. There are a spread of Co–P bond distances ranging from 2.19–2.25 Å. In the fourth Co site, Co is bonded in a 4-coordinate geometry to two equivalent Mn and four P atoms. There are a spread of Co–P bond distances ranging from 2.19–2.25 Å. In the fifth Co site, Co is bonded in a 4-coordinate geometry to four P atoms. There are a spread of Co–P bond distances ranging from 2.18–2.24 Å. In the sixth Co site, Co is bonded in a 4-coordinate geometry to two equivalent Mn and four P atoms. There are a spread of Co–P bond distances ranging from 2.20–2.24 Å. In the seventh Co site, Co is bonded in a 4-coordinate geometry to two equivalent Mn and four P atoms. There are a spread of Co–P bond distances ranging from 2.19–2.25 Å. In the eighth Co site, Co is bonded in a 4-coordinate geometry to four P atoms. There are a spread of Co–P bond distances ranging from 2.20–2.24 Å. There are twelve inequivalent P sites. In the first P site, P is bonded in a 9-coordinate geometry to five Mn, two Fe, and two equivalent Co atoms. In the second P site, P is bonded in a 9-coordinate geometry to five Mn, one Fe, and three Co atoms. In the third P site, P is bonded in a 9-coordinate geometry to five Mn, one Fe, and three Co atoms. In the fourth P site, P is bonded in a 9-coordinate geometry to five Mn, two Fe, and two equivalent Co atoms. In the fifth P site, P is bonded in a 9-coordinate geometry to five Mn, one Fe, and three Co atoms. In the sixth P site, P is bonded in a 9-coordinate geometry to five Mn, one Fe, and three Co atoms. In the seventh P site, P is bonded in a 9-coordinate geometry to five Mn, two equivalent Fe, and two Co atoms. In the eighth P site, P is bonded in a 9-coordinate geometry to five Mn, two equivalent Fe, and two Co atoms. In the ninth P site, P is bonded in a 9-coordinate geometry to five Mn, two equivalent Fe, and two Co atoms. In the tenth P site, P is bonded in a 9-coordinate geometry to five Mn and four Co atoms. In the eleventh P site, P is bonded in a 9-coordinate geometry to five Mn, two equivalent Fe, and two Co atoms. In the twelfth P site, P is bonded in a 9-coordinate geometry to five Mn and four Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

How Interface Evolution at the Nanoscale Dictates Protonic Ceramic Cell Behavior

Understanding the effects of heterointerfaces in nanodevices remains a challenge in interface engineering for systems applied in solid oxide fuel cells, catalysis, sensors, and memristors [1]. Previous studies have shown that the presence of interfaces in ceramic oxide nanodevices affects their impedance properties compared to bulk systems [2]. In this work, we analyze a thin-film model system designed to study the interfaces between representative electrode and electrolyte materials employed in protonic ceramic electrochemical cells for the reversible conversion of hydrogen o electricity. The investigated device features a 21-layer architecture that alternates between an electrode material PBSCF (PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+ϵ ) and a proton-conducting electrolyte BZY (BaZr 0.8 Y 0.2 O 3-δ ), with uniform 20 nm thickness for each layer. Here, the device was fabricated using Pulsed Laser Deposition (PLD) and supported on a conductive Nb-doped STO (Nb-SrTiO 3 ) substrate.

dos Santos, Gabriel T. [Northwestern University, E↗
DOE OSTI2020

Materials Data on Sm4Fe27Co7C2 by Materials Project

Sm4Fe27Co7C2 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are four inequivalent Sm sites. In the first Sm site, Sm is bonded in a distorted single-bond geometry to ten Fe, four Co, and one C atom. There are a spread of Sm–Fe bond distances ranging from 3.03–3.32 Å. There are a spread of Sm–Co bond distances ranging from 3.07–3.34 Å. The Sm–C bond length is 2.55 Å. In the second Sm site, Sm is bonded in a distorted single-bond geometry to eleven Fe, three Co, and one C atom. There are a spread of Sm–Fe bond distances ranging from 3.04–3.31 Å. There are one shorter (3.27 Å) and two longer (3.34 Å) Sm–Co bond lengths. The Sm–C bond length is 2.56 Å. In the third Sm site, Sm is bonded in a distorted single-bond geometry to eleven Fe, three Co, and one C atom. There are a spread of Sm–Fe bond distances ranging from 3.04–3.30 Å. There are one shorter (3.27 Å) and two longer (3.34 Å) Sm–Co bond lengths. The Sm–C bond length is 2.56 Å. In the fourth Sm site, Sm is bonded in a distorted single-bond geometry to eleven Fe, three Co, and one C atom. There are a spread of Sm–Fe bond distances ranging from 3.03–3.30 Å. There are one shorter (3.27 Å) and two longer (3.34 Å) Sm–Co bond lengths. The Sm–C bond length is 2.55 Å. There are seventeen inequivalent Fe sites. In the first Fe site, Fe is bonded in a single-bond geometry to five Fe, two equivalent Co, and one C atom. There are four shorter (2.55 Å) and one longer (2.67 Å) Fe–Fe bond lengths. Both Fe–Co bond lengths are 2.48 Å. The Fe–C bond length is 1.93 Å. In the second Fe site, Fe is bonded in a single-bond geometry to five Fe, two equivalent Co, and one C atom. There are four shorter (2.56 Å) and one longer (2.66 Å) Fe–Fe bond lengths. Both Fe–Co bond lengths are 2.47 Å. The Fe–C bond length is 1.92 Å. In the third Fe site, Fe is bonded to three Sm, seven Fe, and two Co atoms to form distorted FeSm3Fe7Co2 cuboctahedra that share corners with five CoSm2Fe10 cuboctahedra, corners with seven FeSm3Fe7Co2 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with three FeSm3Fe7Co2 cuboctahedra, edges with three CoSm2Fe10 cuboctahedra, faces with three CoSm2Fe10 cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, and a faceface with one CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 66–70°. There are a spread of Fe–Fe bond distances ranging from 2.54–2.67 Å. There are one shorter (2.47 Å) and one longer (2.48 Å) Fe–Co bond lengths. In the fourth Fe site, Fe is bonded to three Sm, seven Fe, and two Co atoms to form distorted FeSm3Fe7Co2 cuboctahedra that share corners with five CoSm2Fe10 cuboctahedra, corners with seven FeSm3Fe7Co2 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with three FeSm3Fe7Co2 cuboctahedra, edges with three CoSm2Fe10 cuboctahedra, faces with three CoSm2Fe9Co cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, and a faceface with one CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 66–70°. There are a spread of Fe–Fe bond distances ranging from 2.54–2.67 Å. Both Fe–Co bond lengths are 2.47 Å. In the fifth Fe site, Fe is bonded in a single-bond geometry to five Fe, two equivalent Co, and one C atom. There are two shorter (2.56 Å) and one longer (2.66 Å) Fe–Fe bond lengths. Both Fe–Co bond lengths are 2.48 Å. The Fe–C bond length is 1.92 Å. In the sixth Fe site, Fe is bonded in a single-bond geometry to four Fe, three Co, and one C atom. Both Fe–Fe bond lengths are 2.55 Å. There are two shorter (2.47 Å) and one longer (2.64 Å) Fe–Co bond lengths. The Fe–C bond length is 1.92 Å. In the seventh Fe site, Fe is bonded to three Sm, six Fe, and three Co atoms to form distorted FeSm3Fe6Co3 cuboctahedra that share corners with five CoSm2Fe10 cuboctahedra, corners with seven FeSm3Fe7Co2 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with three FeSm3Fe7Co2 cuboctahedra, edges with three CoSm2Fe9Co cuboctahedra, faces with three CoSm2Fe9Co cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, and a faceface with one CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 66–70°. There are a spread of Fe–Fe bond distances ranging from 2.53–2.67 Å. There are a spread of Fe–Co bond distances ranging from 2.46–2.63 Å. In the eighth Fe site, Fe is bonded to three Sm, seven Fe, and two Co atoms to form distorted FeSm3Fe7Co2 cuboctahedra that share corners with five CoSm2Fe10 cuboctahedra, corners with seven FeSm3Fe7Co2 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with three FeSm3Fe7Co2 cuboctahedra, edges with three CoSm2Fe10 cuboctahedra, faces with three CoSm2Fe10 cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, and a faceface with one CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 66–70°. There are a spread of Fe–Fe bond distances ranging from 2.54–2.67 Å. Both Fe–Co bond lengths are 2.47 Å. In the ninth Fe site, Fe is bonded in a single-bond geometry to six Fe, two equivalent Co, and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.47–2.74 Å. Both Fe–Co bond lengths are 2.44 Å. The Fe–C bond length is 1.85 Å. In the tenth Fe site, Fe is bonded in a single-bond geometry to five Fe, three Co, and one C atom. There are two shorter (2.47 Å) and one longer (2.73 Å) Fe–Fe bond lengths. There are two shorter (2.44 Å) and one longer (2.74 Å) Fe–Co bond lengths. The Fe–C bond length is 1.84 Å. In the eleventh Fe site, Fe is bonded in a 12-coordinate geometry to two Sm, eight Fe, and two Co atoms. There are a spread of Fe–Fe bond distances ranging from 2.48–2.75 Å. There are one shorter (2.43 Å) and one longer (2.44 Å) Fe–Co bond lengths. In the twelfth Fe site, Fe is bonded in a 12-coordinate geometry to two Sm, seven Fe, and three Co atoms. There are one shorter (2.49 Å) and one longer (2.73 Å) Fe–Fe bond lengths. There are a spread of Fe–Co bond distances ranging from 2.42–2.73 Å. In the thirteenth Fe site, Fe is bonded in a 12-coordinate geometry to two Sm, seven Fe, and three Co atoms. There are one shorter (2.50 Å) and one longer (2.73 Å) Fe–Fe bond lengths. There are a spread of Fe–Co bond distances ranging from 2.42–2.75 Å. In the fourteenth Fe site, Fe is bonded in a 12-coordinate geometry to two Sm, eight Fe, and two Co atoms. There are a spread of Fe–Fe bond distances ranging from 2.49–2.75 Å. There are one shorter (2.43 Å) and one longer (2.44 Å) Fe–Co bond lengths. In the fifteenth Fe site, Fe is bonded in a 5-coordinate geometry to one Sm, ten Fe, and three Co atoms. The Fe–Fe bond length is 2.36 Å. All Fe–Co bond lengths are 2.64 Å. In the sixteenth Fe site, Fe is bonded in a 5-coordinate geometry to one Sm, ten Fe, and three Co atoms. There are one shorter (2.64 Å) and two longer (2.65 Å) Fe–Co bond lengths. In the seventeenth Fe site, Fe is bonded in a 1-coordinate geometry to one Sm, nine Fe, and four Co atoms. There are a spread of Fe–Co bond distances ranging from 2.33–2.66 Å. There are five inequivalent Co sites. In the first Co site, Co is bonded to two Sm, nine Fe, and one Co atom to form distorted CoSm2Fe9Co cuboctahedra that share corners with four FeSm3Fe7Co2 cuboctahedra, corners with four CoSm2Fe10 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with four FeSm3Fe7Co2 cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, and faces with four CoSm2Fe9Co cuboctahedra. The corner-sharing octahedral tilt angles are 45°. The Co–Co bond length is 2.63 Å. In the second Co site, Co is bonded to two Sm and ten Fe atoms to form distorted CoSm2Fe10 cuboctahedra that share corners with four FeSm3Fe7Co2 cuboctahedra, corners with four CoSm2Fe10 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with four FeSm3Fe7Co2 cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, and faces with four CoSm2Fe9Co cuboctahedra. The corner-sharing octahedral tilt angles are 45°. In the third Co site, Co is bonded to two Sm and ten Fe atoms to form distorted CoSm2Fe10 cuboctahedra that share corners with four CoSm2Fe10 cuboctahedra, corners with eight FeSm3Fe7Co2 cuboctahedra, edges with four FeSm3Fe7Co2 cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, faces with four CoSm2Fe10 cuboctahedra, and faces with two equivalent CSm2Fe4 octahedra. In the fourth Co site, Co is bonded to two Sm, nine Fe, and one Co atom to form distorted CoSm2Fe9Co cuboctahedra that share corners with four CoSm2Fe9Co cuboctahedra, corners with eight FeSm3Fe7Co2 cuboctahedra, edges with four FeSm3Fe7Co2 cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, faces with four CoSm2Fe9Co cuboctahedra, and faces with two equivalent CSm2Fe4 octahedra. The Co–Co bond length is 2.65 Å. In the fifth Co site, Co is bonded in a 1-coordinate geometry to one Sm, ten Fe, and three Co atoms. There are two inequivalent C sites. In the first C site, C is bonded to two Sm and four Fe atoms to form CSm2Fe4 octahedra that share corners with two CoSm2Fe9Co cuboctahedra, corners with eight FeSm3Fe7Co2 cuboctahedra, faces with four FeSm3Fe7Co2 cuboctahedra, and faces with four equivalent CoSm2Fe10 cuboctahedra. In the second C site, C is bonded to two Sm and four Fe atoms to form CSm2Fe4 octahedra that share corners with two CoSm2Fe9Co cuboctahedra, corners with eight FeSm3Fe7Co2 cuboctahedra, faces with four FeSm3Fe6Co3 cuboctahedra, and faces with four equivalent CoSm2Fe9Co cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeCoSn by Materials Project

FeCoSn crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Fe is bonded in a 8-coordinate geometry to two equivalent Fe, six equivalent Co, and six equivalent Sn atoms. Both Fe–Fe bond lengths are 2.60 Å. All Fe–Co bond lengths are 2.80 Å. All Fe–Sn bond lengths are 2.80 Å. Co is bonded in a 5-coordinate geometry to six equivalent Fe and five equivalent Sn atoms. There are three shorter (2.48 Å) and two longer (2.60 Å) Co–Sn bond lengths. Sn is bonded in a 11-coordinate geometry to six equivalent Fe and five equivalent Co atoms.

36 MATERIALS SCIENCE↗