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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ba(HO)2 by Materials Project

Ba(OH)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 2-coordinate geometry to five H1+ and seven O2- atoms. There are a spread of Ba–H bond distances ranging from 2.68–2.91 Å. There are a spread of Ba–O bond distances ranging from 2.72–3.04 Å. In the second Ba2+ site, Ba2+ is bonded in a 3-coordinate geometry to three O2- atoms. There are a spread of Ba–O bond distances ranging from 2.64–2.71 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to two equivalent Ba2+ and one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one Ba2+ and one O2- atom. The H–O bond length is 0.99 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one Ba2+ and one O2- atom. The H–O bond length is 0.97 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one Ba2+ and one O2- atom. The H–O bond length is 0.98 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to three Ba2+ and one H1+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to three Ba2+ and one H1+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to two Ba2+ and one H1+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to two equivalent Ba2+ and one H1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(Ge3Pt)4 by Materials Project

Ba(PtGe3)4 crystallizes in the cubic Im-3 space group. The structure is three-dimensional. Ba is bonded to twelve equivalent Ge atoms to form BaGe12 cuboctahedra that share faces with eight equivalent PtGe6 octahedra. All Ba–Ge bond lengths are 3.43 Å. Pt is bonded to six equivalent Ge atoms to form distorted PtGe6 octahedra that share corners with six equivalent PtGe6 octahedra and faces with two equivalent BaGe12 cuboctahedra. The corner-sharing octahedral tilt angles are 60°. All Pt–Ge bond lengths are 2.55 Å. Ge is bonded in a 2-coordinate geometry to one Ba, two equivalent Pt, and two equivalent Ge atoms. There are one shorter (2.53 Å) and one longer (2.70 Å) Ge–Ge bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(C2N3)2 by Materials Project

Ba(CN2)2(CN)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional and consists of four CN clusters and one Ba(CN2)2 framework. In each CN cluster, there are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a linear geometry to two N3- atoms. There is one shorter (1.18 Å) and one longer (1.28 Å) C–N bond length. In the second C4+ site, C4+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.22 Å. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a linear geometry to two C4+ atoms. In the second N3- site, N3- is bonded in a single-bond geometry to one C4+ atom. In the Ba(CN2)2 framework, Ba2+ is bonded in a distorted pentagonal planar geometry to five N3- atoms. There are a spread of Ba–N bond distances ranging from 2.78–2.89 Å. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a bent 150 degrees geometry to two N3- atoms. There is one shorter (1.23 Å) and one longer (1.37 Å) C–N bond length. In the second C4+ site, C4+ is bonded in a linear geometry to two N3- atoms. There is one shorter (1.20 Å) and one longer (1.28 Å) C–N bond length. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted water-like geometry to one Ba2+ and two C4+ atoms. In the second N3- site, N3- is bonded in a distorted single-bond geometry to one C4+ and one N3- atom. The N–N bond length is 1.23 Å. In the third N3- site, N3- is bonded in a distorted trigonal planar geometry to two equivalent Ba2+ and one N3- atom. In the fourth N3- site, N3- is bonded in a 1-coordinate geometry to two equivalent Ba2+ and one C4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(H9O5)2 by Materials Project

Ba(H3O4)2(H2)4(H2O)2 crystallizes in the monoclinic P2_1/c space group. The structure is one-dimensional and consists of sixteen hydrogen molecules; eight water molecules; and two Ba(H3O4)2 ribbons oriented in the (0, 1, 0) direction. In each Ba(H3O4)2 ribbon, Ba2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ba–O bond distances ranging from 2.43–3.17 Å. There are six inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.01 Å. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted water-like geometry to one Ba2+ and two H1+ atoms. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ba2+ and one O2- atom. The O–O bond length is 1.29 Å. In the third O2- site, O2- is bonded in a water-like geometry to one Ba2+ and two H1+ atoms. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to one O2- atom. The O–O bond length is 1.44 Å. In the fifth O2- site, O2- is bonded in a single-bond geometry to one Ba2+, one H1+, and one O2- atom. The O–O bond length is 1.49 Å. In the sixth O2- site, O2- is bonded in a distorted L-shaped geometry to one Ba2+ and one O2- atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one Ba2+ and one O2- atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one Ba2+, one H1+, and one O2- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(CoGe)2 by Materials Project

Ba(CoGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba is bonded in a distorted body-centered cubic geometry to eight equivalent Ge atoms. All Ba–Ge bond lengths are 3.42 Å. Co is bonded to four equivalent Ge atoms to form a mixture of distorted corner and edge-sharing CoGe4 tetrahedra. All Co–Ge bond lengths are 2.34 Å. Ge is bonded in a 8-coordinate geometry to four equivalent Ba and four equivalent Co atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(TeMo)6 by Materials Project

BaMo6Te6 crystallizes in the hexagonal P-6 space group. The structure is three-dimensional. Ba is bonded in a 9-coordinate geometry to nine Te atoms. There are six shorter (3.58 Å) and three longer (3.73 Å) Ba–Te bond lengths. There are two inequivalent Mo sites. In the first Mo site, Mo is bonded in a 10-coordinate geometry to six Mo and four Te atoms. There are a spread of Mo–Mo bond distances ranging from 2.68–2.79 Å. There are a spread of Mo–Te bond distances ranging from 2.83–2.89 Å. In the second Mo site, Mo is bonded in a 10-coordinate geometry to six Mo and four Te atoms. Both Mo–Mo bond lengths are 2.66 Å. There are a spread of Mo–Te bond distances ranging from 2.83–2.90 Å. There are two inequivalent Te sites. In the first Te site, Te is bonded in a 6-coordinate geometry to two equivalent Ba and four Mo atoms. In the second Te site, Te is bonded in a 5-coordinate geometry to one Ba and four Mo atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(Cd2Pt)2 by Materials Project

Ba(PtCd2)2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Ba is bonded to six equivalent Pt atoms to form a mixture of distorted edge and corner-sharing BaPt6 octahedra. The corner-sharing octahedral tilt angles are 40°. There are two shorter (3.37 Å) and four longer (3.50 Å) Ba–Pt bond lengths. Pt is bonded in a 9-coordinate geometry to three equivalent Ba and six equivalent Cd atoms. There are four shorter (2.83 Å) and two longer (2.85 Å) Pt–Cd bond lengths. Cd is bonded in a distorted trigonal non-coplanar geometry to three equivalent Pt atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(H9O5)2 by Materials Project

Ba(HO)10(H2)4 crystallizes in the monoclinic P2_1/c space group. The structure is one-dimensional and consists of sixteen hydrogen molecules and two Ba(HO)10 ribbons oriented in the (0, 1, 0) direction. In each Ba(HO)10 ribbon, Ba2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ba–O bond distances ranging from 2.49–2.97 Å. There are ten inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.02 Å) and one longer (1.59 Å) H–O bond length. In the third H1+ site, H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.66 Å) H–O bond length. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.01 Å. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the tenth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to two H1+ atoms. In the second O2- site, O2- is bonded in a single-bond geometry to one Ba2+, one H1+, and one O2- atom. The O–O bond length is 1.49 Å. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Ba2+ and one O2- atom. The O–O bond length is 1.30 Å. In the fourth O2- site, O2- is bonded in a single-bond geometry to one Ba2+, one H1+, and one O2- atom. The O–O bond length is 1.42 Å. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to one O2- atom. In the sixth O2- site, O2- is bonded in a water-like geometry to one Ba2+ and two H1+ atoms. In the seventh O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three H1+ atoms. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Ba2+ and one O2- atom. In the ninth O2- site, O2- is bonded in a water-like geometry to one Ba2+ and two H1+ atoms. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to one Ba2+, one H1+, and one O2- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Electronic Structure, Chemical Bonding and Electrocatalytic Activity of Novel Ba(Fe0.7Ta0.3)O3-d Compounds

Ba(Fe0.7Ta0.3)O3-d (BFTO) compounds were synthesized using conventional, high-temperature solid-state ceramic reaction method by varying the sintering temperature (Ts=1200-1350 °C). The crystal structure, electronic structure and electrocatalytic activity of BFTO compounds were evaluated. Processing temperature induced phase transformations and structural quality influences the electronic structure and electrocatalytic activity of BFTO compounds. At Ts=1200 oC, Ba(Fe0.7Ta0.3)O3-d stabilizes in mixed phase of orthorhombic + rhombohedral phase (Amm2 + R3m). With increasing Ts (=1250 oC), Ba(Fe0.7Ta0.3)O3-d ceramics stabilize in tetragonal + rhombohedral [P4mm + R3m] mixed phase with a variation in the quantity of respective phases. High-resolution X-ray photoelectron spectroscopy of constituent elements, namely, Ba 3d, Fe2p, Ta 4f and O 1s reveal the electronic structure changes due to changes in chemical environment resulted from structural transformation. The electrocatalytic activity of BFTO was evaluated towards hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). Though all the samples demonstrated appreciable electrocatalytic properties, the best electrochemical catalytic activity was shown by BFTO samples sintered at 1350 °C. BFTO-1350 oC showed an onset potential of -0.690 V vs. RHE for HER and an onset potential of 0.73 V vs. RHE for ORR indicating its significant electrocatalytic performance. A general increase in activity with sintering temperature is potentially due to the improved structural quality of the BFTO ceramics. In addition to offering the fundamental insights into solid state materials based on doped BaTiO3 for electrocatalysis, the present work may contribute to the design and development of materials for high-temperature electrocatalytic converters.

Ba(Fe0.7Ta0.3)O3-d, Phase Transformation↗
DOE OSTI2020

Crystal and Electronic Structures of A 2 NaIO 6 Periodate Double Perovskites (A = Sr, Ca, Ba): Candidate Wasteforms for I-129 Immobilization

The synthesis, structure, and thermal stability of the periodate double perovskites A 2 NaIO 6 (A= Ba, Sr, Ca) were investigated in the context of potential application for the immobilization of radioiodine. A combination of X-ray diffraction and neutron diffraction, Raman spectroscopy, and DFT simulations were applied to determine accurate crystal structures of these compounds and understand their relative stability. The compounds were found to exhibit rock-salt ordering of Na and I on the perovskite B-site; Ba 2 NaIO 6 was found to adopt the Fm- 3 m aristotype structure, whereas Sr 2 NaIO 6 and Ca 2 NaIO 6 adopt the P 2 1 / n hettotype structure, characterized by cooperative octahedral tilting. DFT simulations determined the Fm- 3 m and P 2 1 / n structures of Ba 2 NaIO 6 to be energetically degenerate at room temperature, whereas diffraction and spectroscopy data evidence only the presence of the Fm- 3 m phase at room temperature, which may imply an incipient phase transition for this compound. The periodate double perovskites were found to exhibit remarkable thermal stability, with Ba 2 NaIO 6 only decomposing above 1050 °C in air, which is apparently the highest recorded decomposition temperature so far recorded for any iodine bearing compound. As such, these compounds offer some potential for application in the immobilization of iodine-129, from nuclear fuel reprocessing, with an iodine incorporation rate of 25–40 wt%. The synthesis of these compounds, elaborated here, is also compatible with both current conventional and future advanced processes for iodine recovery from the dissolver off-gas.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Molecular Cage Reports on Its Contents: Spectroscopic Signatures of Cryo-Cooled K + - and Ba 2+ -Benzocryptand Complexes

UV photofragment spectroscopy and IR–UV double resonance methods are used to determine the structure and spectroscopic responses of a three-dimensional [2.2.2]-benzocryptand cage to the incorporation of a single K + or Ba 2+ imbedded inside it (labeled as K + -BzCrypt, Ba 2+ -BzCrypt). We studied the isolated ion-cryptand complex under cryo-cooled conditions, brought into the gas phase by nano-electrospray ionization. Incorporation of a phenyl ring in place of the central ethyl group in one of the three N-CH 2 -CH 2 -O-CH 2 -CH 2 -O-CH 2 -CH 2 -N chains provides a UV chromophore whose S 0 –S 1 transition we probe. K + -BzCrypt and Ba 2+ -BzCrypt have their S 0 –S 1 origin transitions at 35,925 and 36,446 cm –1 , respectively, blue-shifted by 174 and 695 cm –1 from that of 1,2-dimethoxybenzene. These origins are used to excite a single conformation of each complex selectively and record their IR spectra using IR–UV dip spectroscopy. The alkyl CH stretch region (2800–3000 cm –1 ) is surprisingly sensitive to the presence and nature of the encapsulated ion. We carried out an exhaustive conformational search of cage conformations for K + -BzCrypt and Ba 2+ -BzCrypt, identifying two conformations (A and B) that lie below all others in energy. Here, we extend our local mode anharmonic model of the CH stretch region to these strongly bound ion-cage complexes to predict conformation-specific alkyl CH stretch spectra, obtaining quantitative agreement with experiment for conformer A, the gas-phase global minimum. The large electrostatic effect of the charge on the O- and N-lone pairs affects the local mode frequencies of the CH 2 groups adjacent to these atoms. The localized CH 2 scissors modes are pushed up in frequency by the adjacent O/N-atoms so that their overtones have little effect on the alkyl CH stretch region. However, the localized CH 2 wags are nearly degenerate and strongly coupled to one another, producing an array of delocalized wag normal modes, whose highest frequency members reach up above 1400 cm –1 . As such, their overtones mix significantly with the CH stretch modes, most notably involving the CH 2 symmetric stretch fundamentals of the central ethyl groups in the all-alkyl chains and the CH stretches adjacent to the N-atoms and antiperiplanar to the nitrogen lone pair.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

The Role of Exciton Binding Energy on LO phonon Broadening and Polaron Formation in (BA) 2 PbI 4 Ruddlesden-Popper Films

The effect of carrier–carrier and carrier–phonon interactions is presented in n = 1 (2D) (BA) 2 PbI 4 Ruddlesden–Popper thin films, and their effect is compared to that of conventional MAPbI 3 . While temperature-dependent photoluminescence shows the well-studied structural phase transitions and evidence of longitudinal optical (LO) phonon scattering in MPbI 3 , the 2D (BA) 2 PbI 4 films produce subtler properties. At low temperatures, evidence of two competing intrinsic exciton transitions is observed (P1 and P3), in addition to several extrinsic transitions attributed to the impurities in the (BA) 2 PbI 4 film. At higher temperatures, (BA) 2 PbI 4 is dominated by the two intrinsic excitons that are attributed to varying degrees of localization caused by deformations of the PbI 4 framework mediated by structural relaxation. Although both exciton complexes are well separated from the continuum (490 meV or greater), their interaction with phonons is quite different. In the case of the more strongly bound complex (P3), the strong excitonic nature and short-range interaction are mediated by the emission of LO phonon replicas. In the case of the exciton with the smaller binding energy (P1), the more extended wavefunction manifests itself in strong carrier–phonon scattering and evidence of large, stable polarons.

2D perovskites↗
DOE OSTI2025

Synthesis, Crystal Structure, and Optical Properties of the Barium meta -Pertechnetate Ba[TcO 4 ] 2

High-quality single crystals of the colorless title compound Ba[ 99 TcO 4 ] 2 were prepared from radioactive, isotope-pure 99 TcO 2 by oxidation with H 2 O 2 in an aqueous ammonia solution and subsequent cation metathesis using an ion-exchange column. Single-crystal X-ray diffraction revealed Ba[TcO 4 ] 2 to crystallize isotopically to Ba[MnO 4 ] 2 in the orthorhombic space group Fddd with the lattice parameters a = 747.34(5) pm, b = 1244.08(7) pm, and c = 1511.23(9) pm for Z = 8. Its crystal structure features [BaO 12 ] 22- icosahedra surrounded by ten [TcO 4 ] - tetrahedra connected via two edges and eight corners. The optical properties of Ba[TcO 4 ] 2 investigated by UV-vis spectroscopy show the broad O 2- → Tc 7+ ligand-to-metal charge transfer (2p → 4d) process within these discrete [TcO 4 ]- anions at an absorption maximum of around 350 nm.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Dopant site-dependent luminescence from rare-earth doped dibarium octafluorohafnate Ba 2 HfF 8 nanocubes for radiation detection

Development of new host materials containing heavy elements for radiation detection is highly desirable. In this work, dibarium octafluorohafnate, Ba 2 HfF 8 , doped with rare-earth ions, was synthesized as cube-shaped nanocrystals via a facile hydrothermal method. The host lattice contains two Ba 2+ crystallographic sites, and dopants on these sites exhibit site-dependent photoluminescence (PL), cathodoluminescence (CL) and X-ray excited radioluminescence (RL) characteristics. Single doping contents were optimized as 25 mol% Tb 3+ and 5 mol% Eu 3+ . In Ba 2 HfF 8 :Tb 3+ –Eu 3+ codoped nanocrystals, preferrable occupation of Eu 3+ and Tb 3+ at two different Ba 2+ sites in the host lattice was observed. The nanocubes exhibited enhanced emissions over micron sized particles. In PL, the presence of Tb3+ ions significantly enhanced the emission intensity of Eu 3+ ions due to energy transfer from the Tb 3+ to Eu 3+ ions, while under high-energy irradiation in CL or RL, Tb 3+ emission was intensified. X-ray induced RL with afterglow in seconds was observed. Finally, it was found that the codoped sample showed higher sensitivity than the singly doped sample, indicating that codoping is an effective strategy to develop a scintillator with this host structure for high-energy radiation detection.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Ba 1−x Sr x FeO 3−δ as an improved oxygen storage material for chemical looping air separation: a computational and experimental study

Chemical looping air separation (CLAS) is a promising technology to generate oxygen-rich gas streams to enable efficient carbon dioxide capture during fossil fuel combustion or gasification. CLAS relies on the capture and release of oxygen from the atmosphere using the redox properties of an oxygen-selective solid oxide carrier. This study investigates the redox characteristics of Ba 1−x Sr x FeO 3−δ (0.0 ≤ x ≤ 0.417, 0.0 ≤ δ ≤ 0.5) using a combination of density functional theory (DFT) calculations and experimental verification using X-ray diffraction, thermogravimetric analysis, and oxygen-temperature-programmed desorption. The DFT computed energies of the Ba 1−x Sr x FeO 3−δ perovskites reveal a composition-dependent transition from hexagonal to cubic phases as the Sr-concentration or oxygen vacancy concentration increases. Oxygen vacancy formation energies of the cubic perovskites are found to be lower than those of their hexagonal counterparts. A low oxygen diffusion barrier of ∼1 eV combined with the thermodynamic preference of Ba 1−x Sr x FeO 3−δ compositions that form in a cubic phase suggests them as promising candidates for oxygen storage applications. The experimental results corroborate this finding by identifying Ba 0.75 Sr 0.25 FeO 3−δ in the cubic phase as an optimal composition offering low-temperature oxygen storage capacities comparable to that of the state-of-the-art Sr 0.75 Ca 0.25 FeO 3−δ perovskite oxygen storage material at 325 °C and 350 °C.

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

Ultrafast pre-solvated dodecane hole capture and subsequent damage of used nuclear fuel extraction ligands DEHBA, DEH i BA, HONTA, CMPO, HEH[EHP] and TBP

Here, two classes of used nuclear fuel (UNF) extraction ligands, amide (DEHBA, DEH i BA, HONTA) and organophosphorus (CMPO, HEH[EHP], TBP), were selected to study radiation induced damage at picosecond to nanosecond timescale using electron pulse radiolysis in n-dodecane (DD) and supported by quantum chemical calculations. Spectra after radiolysis of 200 mM extraction ligands were recorded in DD/0.3 M DCM. Absorption peaks at 365, 365, 400 and 387 nm in case of DEHBA, DEH i BA, HONTA and CMPO respectively are assigned to triplet excited states. Additional absorption peaks at 420, 460 and 600 nm of DEHBA, DEH i BA and HONTA respectively were identified as due to ligand radical cations. A concentration dependent absorption peak at 600 nm in the case of CMPO was observed and assigned due to a combination of CMPO˙ + , (CMPO) 2 ˙ + and possibly a radical degradation product of CMPO. Weak absorption peaks at 650 and 550 nm in case of HEH[EHP] and TBP were observed and tentatively assigned to their radical cations. A two-component DD˙ + decay in the presence of ligands was observed due to different ligand oxidation mechanisms: ultrafast capture of pre-solvated DD holes and diffusive capture of solvated DD holes. At high extraction ligand concentrations (>100 mM), the majority of DD holes were captured via the ultrafast pre-solvated pathway in <10 ps with C 37 values of 389, 401, 270, 374, 458 and 340 mM for DEHBA, DEHiBA, HONTA, CMPO, HEH[EHP] and TBP respectively. Following ultrafast capture, the remainder of DD holes became solvated and were captured with k = (2.32 ± 0.13), (1.78 ± 0.12), (1.38 ± 0.2), (0.98 ± 0.081), (1.09 ± 0.08) and (1.77 ± 0.046) × 10 10 for DEHBA, DEH i BA, HONTA, CMPO, HEH[EHP] and TBP respectively. Subsequent hole transfer from the extraction ligands˙ + to the low IP solute tri-p-tolylamine (TTA) showed only 4–16% hole transfer, most likely indicating ligand˙ + degradation in 0.9–4.6 ns.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2026

Canted antiferromagnetism and spin reorientation in corner-shared single chain quasi-one-dimensional Ba 2 ⁢FeSe 3

Here, we report the canted antiferromagnetic (AFM) structure together with a spin reorientation in a single chain quasi-one-dimensional (Q-1D) iron chalcogenide Ba 2⁢ FeSe 3 . Ba 2 ⁢FeSe 3 crystallizes in Pnma (No. 62) orthorhombic structure with linear single iron chains consisting of corner-shared distorted FeSe 4 tetrahedra along the 𝑏 axis. Ba 2 ⁢FeSe 3 is a narrow-gap semiconductor and orders AFM below 60 K. Modeling of neutron powder diffraction data reveals a canted AFM ground state of magnetic space group 𝑃⁢𝑎⁢21/𝑐 (BNS No. 14.80) with commensurate propagation vector 𝐤 =(0, $\frac{1}{2}$, 0), where the Fe ion spins are AFM aligned with up-down-up-down (↑−↓−↑−↓) sequence along the Q-1D chain direction of the 𝑏 axis. In the magnetically ordered state, the canting of magnetic moments reorients from the 𝑎⁢𝑐 plane to the 𝑎⁢𝑏 plane below 30 K, with a 10° tilting angle toward the 𝑎 axis, and the magnetic moment does not induce a net moment in either orientation. The density functional theory results indicate that an ↑−↓−↑−↓ AFM state is stabilized along the chain direction. In this work, we elucidate the unique canted AFM of the iron chalcogenide and pave the way for searching exotic physics in Q-1D Ba 2⁢ FeSe 3 .

Gao, Fei [Univ. of Texas at Dallas, Richardson, TX↗
DOE OSTI2020

Evidence of Ba-substitution induced spin-canting in the magnetic Weyl semimetal EuCd 2 As 2

Recently EuCd 2 As 2 was predicted to be a magnetic Weyl semimetal with a lone pair of Weyl nodes generated by A-type antiferromagnetism and protected by a rotational symmetry. However, it was soon discovered that the actual magnetic structure broke the rotational symmetry and internal pressure was later suggested as a route to stabilize the desired magnetic state. In this work we test this prediction by synthesizing a series of Eu 1-x BaxCd 2 As 2 single crystals and studying their structural, magnetic, and transport properties via both experimental techniques and first-principles calculations. We find that small concentrations of Ba (~3%–10%) lead to a small out-of-plane canting of the Eu moment. However, for higher concentrations this effect is suppressed and a nearly in-plane model is recovered. Studying the transport properties we find that all compositions show evidence of an anomalous Hall effect dominated by the intrinsic mechanism as well as large negative magnetoresistances in the longitudinal channel. A nonmonotonic evolution of the transport properties is seen across the series which correlates to the proposed canting suggesting canting may enhance the topological effects. Careful density functional theory calculations using an all-electron approach revise prior predictions finding a purely ferromagnetic ground state with in-plane moments for both the EuCd 2 As 2 and Eu 0.5 Ba 0.5 Cd 2 As 2 compounds, corroborating our experimental findings. This work suggests that Ba substitution can tune the magnetic properties in unexpected ways which correlate to changes in measures of topological properties, encouraging future work to locate the ideal Ba concentration for Eu moment canting.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗