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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Unexpected Hydride: Ce 4 B 2 C 2 H 2.42 , a Stuffed Variant of the Nd 2 BC Structure Type

Ce 4 B 2 C 2 H 2.42 was grown as large crystals from a cerium/copper eutectic flux. The structure was characterized by single-crystal X-ray and neutron diffraction and was found to be a stuffed variant of Nd 2 BC with the addition of two interstitial hydrogen positions. The tetrahedral hydrogen position is fully occupied, while the octahedral position has an occupancy of 42(3)%. Initial synthesis was due to hydrogen contamination of the cerium metal but has been successfully repeated using anthracene as a carbon and hydrogen source. Density of states calculations suggest that the incorporation of hydrogen stabilizes the compound with respect to the nonhydrided model. Magnetic susceptibility data show a complex magnetic ordering at 7.7 K that originates from the localized electron on the Ce 3+ in the structure. The trivalent state is also supported by X-ray photoelectron spectroscopy measurements. Heat capacity and electrical resistivity data show that the phase transition is broad in temperature, which may be due to structural disorder. Furthermore, the large low temperature value of C/T also indicates possible heavy fermion behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nd(BC)2 by Materials Project

NdB2C2 crystallizes in the tetragonal P4_2/mmc space group. The structure is three-dimensional. Nd2+ is bonded in a 8-coordinate geometry to eight equivalent C4- atoms. All Nd–C bond lengths are 2.80 Å. B3+ is bonded in an L-shaped geometry to two equivalent C4- atoms. Both B–C bond lengths are 1.62 Å. C4- is bonded in a 2-coordinate geometry to four equivalent Nd2+, two equivalent B3+, and one C4- atom. The C–C bond length is 1.43 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nd(BC)2 by Materials Project

NdB2C2 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Nd2+ is bonded in a body-centered cubic geometry to eight equivalent C4- atoms. All Nd–C bond lengths are 2.79 Å. B3+ is bonded in a distorted trigonal planar geometry to three equivalent C4- atoms. There is one shorter (1.54 Å) and two longer (1.62 Å) B–C bond length. C4- is bonded in a 3-coordinate geometry to four equivalent Nd2+ and three equivalent B3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Laser resonance ionization spectroscopy of thorium

High-lying Rydberg and autoionizing (AI) states of thorium (Th) have been studied via resonance laser ionization spectroscopy at both TRIUMF Canada’s particle accelerator center and Oak Ridge National Lab (ORNL). Multiple Rydberg series converging to the ionization potential (IP) were observed via different stepwise laser excitation schemes and were assigned to be the 6d 2 7s ( 4 F 3/2 ) np, nd, and nf series. Analysis of these series enabled the determination of the IP to be 50 868.735(54) cm −1 , which improved the precision by two orders of magnitude over the current adopted NIST value of 50 867(2) cm −1 . Additionally, four AI Rydberg series were identified and assigned to nf and nd series converging to the 6d 2 7s 4 F 5/2 and 6d7s 2 2 D 3/2 metastable states of Th + . In conclusion, the measured energies of the Rydberg and AI Rydberg states are reported, and observed perturbations within the series are discussed.

Rydberg series↗
DOE OSTI2026

Low-temperature magnetic structure and lattice response in SmCuAs 2

We investigated the structural and magnetic properties of single-crystalline SmCuAs 2 using high-resolution synchrotron x-ray diffraction and x-ray resonant magnetic scattering (XRMS) at the Sm 𝐿 2 and 𝐿 3 edges. Temperature-dependent diffraction measurements confirm that SmCuAs2 maintains its tetragonal symmetry from room temperature down to 8 K, with lattice parameters showing anomalous behavior below the resistivity minimum (𝑇≈30K). Notably, the c-axis lattice parameter exhibits a plateau and subsequent increase near the Néel temperature, indicating magnetoelastic coupling. XRMS measurements reveal a commensurate antiferromagnetic structure with a propagation vector 𝒒=(0,0,0.5). Our measurement shows that the Sm moments are aligned within the 𝒂𝒃 plane and arranged in a ++−− stacking along the 𝒄 axis. Comparison with related 𝑅⁢𝐸⁢CuAs 2 compounds (RE = Pr, Nd, and Gd) suggests that in-plane moment orientation and associated magnetic frustration play a key role in the emergence of the resistivity minimum. Differences in spin-orbit and magnetoelastic coupling across the series highlight their importance in governing low-temperature transport behavior.

36 MATERIALS SCIENCE↗