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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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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Magnetic pair distribution function and half polarized neutron powder diffraction at the HB-2A powder diffractometer

Local magnetic order and anisotropy are often central for understanding fundamental behavior and emergent functional properties in quantum materials and beyond. Advances in neutron powder diffraction experiments and analysis tools now allow for quantitative determination. Here, we demonstrate this here with complementary total neutron scattering and polarized neutron measurements on the HB-2A neutron powder diffractometer at the High Flux Isotope Reactor (HFIR). In recent years, magnetic pair distribution function (mPDF) analysis has emerged as a powerful technique for probing local magnetic spin ordering of magnetic materials. This method can be broadly applied to any magnetic material but is particularly effective for studying systems with short-range magnetic order, such as materials with reduced dimensionality, geometrically frustrated magnets, thermoelectrics, multiferroics, and correlated paramagnets. Magnetic anisotropy often underpins the short-range order adopted. Half-polarized neutron powder diffraction (pNPD) can be used to determine the local susceptibility tensor on the magnetic sites to quantify the magnetic anisotropy. Combining the techniques of mPDF and pNPD can therefore provide valuable insights into local magnetic behavior. A series of measurements optimized for these techniques are presented as exemplar cases focused on frustrated materials where short-range order dominates, these include measurements to ultra-low temperature (<100 mK) not typically accessible for such experiments.

Half polarized neutron scattering↗
DOE OSTI2023

Considerations for quantitative in situ X-ray powder diffraction studies of solid-state reactions

The importance of sample preparation in collecting high-fidelity powder diffraction data suitable for quantitative structure and phase analysis is well established. Such powder diffraction experiments are increasingly being appliedin situ, during reactions, to explore solid-state reactivity. When appliedin situ, X-ray diffraction is widely used to gain insight into the mechanism and kinetics, and to identify dynamic intermediate states. Here, using a model ion-exchange reaction (NaFeO 2 + LiCl → LiFeO 2 + NaCl), we show that sample preparation not only influences the fidelity of powder diffraction analysis but also impacts the observed reaction progress. Specifically, we found that the observed reaction progress can differ by ∼50% depending on the capillary sample preparation. Thus, forin situdiffraction studies of solid-state reactions, packing fraction is an important and previously unrecognized consideration that impacts reproducibility and fidelity of the reaction study.

Chemistry↗
DOE OSTI2023

Machine Learning Based System for Automated Estimation of Crystal Unit Cell Parameters from X-ray Diffraction Powder Patterns (MLCell) v0.1

This software uses machine learning models to perform inference on X-ray diffraction powder patterns, output from a diffractometer, to estimate all 6 unit cell parameters of crystalline lattices. Novel aspects of this software originated from the incorporation of concepts from crystallography to an ML-based approach; The resulting method achieves new performance capabilities without significant loss of accuracy and with less computationally intensive models.

Oklejas, Vanessa↗
DOE OSTI2026

High-pressure neutron powder diffraction study of an arsenolite deuterium inclusion compound: structure and formation kinetics

High-pressure variable-temperature neutron powder diffraction was employed to investigate the synthesis and structural properties of arsenolite (As 4 O 6 ), a cubic arsenic( III ) oxide polymorph, and its inclusion compound with deuterium. The compound forms with the stoichiometry As 4 O 6 ·2D 2 , consistent with earlier findings. At 295 K and 1.96(2) GPa, D 2 molecules occupy the 16c site (0, 0, 0) and are aligned along the <111> direction. The diffraction data suggest that the D 2 molecules at this site become rotationally disordered upon decompression to 0.78(2) GPa at 120 K, while no occupancy is observed at the 8a position (⅛, ⅛, ⅛) under any of the studied conditions. The kinetic data of the high-pressure inclusion compound synthesis at 1.56(2) and 1.96(2) GPa were analyzed using the Avrami model. The Avrami exponent, 0.135(16), remains invariant with pressure, demonstrating that the reaction topochemistry is unaffected by compression. Similarly, the reaction rates, 0.29(3) and 0.23(3) min −0.135 at 1.56(2) and 1.96(2) GPa, respectively, exhibit negligible pressure dependence and suggest a surprisingly low activation volume of 1.6 cm 3 mol −1 for the reaction. These results provide detailed insight into the structural dynamics and kinetics of deuterium inclusion in arsenolite under high pressure.

Guńka, Piotr A. [Warsaw University of Technology (↗
DOE OSTI2025

Anthropogenic Influences on the Chemical and Mineral Composition in Pond Sediment by X-Ray Absorption Spectroscopy and X-Ray Powder Diffraction

Manmade detention ponds have historically been impacted by anthropogenic activities such as rainwater runoff, car emissions, and drainage from infrastructures, which can lead to complications for pond ecosystems. Sediment samples collected from the northern, southern, western, and eastern regions of a small pond on a suburban high school campus on Long Island, NY, were analyzed for potential chemical changes resulting from an inundation of water by a broken water main. Incorporating synchrotron X-ray techniques, sediment was analyzed using Submicron Resolution Spectroscopy, Tender Energy X-ray Spectroscopy, and X-ray Powder Diffraction to examine heavy metals, light elements, and minerals. Results include a Zn:Cu ratio increase from 4:1 to 10:1 in the eastern zone and a higher heavy metal presence in the western zone for all elements examined, with greater distribution throughout the pond post-inundation. Lighter elements appear to remain relatively unchanged. The appearance of diopside in the eastern zone post-inundation samples suggests contamination from the water main break, while the presence of carbonate minerals in the western zone is consistent with erosion of asphalt material from the adjacent parking lot.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Cation Adaptive Structures Based on Manganese Cyanide Prussian Blue Analogues: Application of Powder Diffraction Data to Solve Complex, Unprecedented Stoichiometries and New Structure Types

Abstract A Mn(II) salt and A + CN − under anaerobic conditions react to form 2‐D and 3‐D extended structured compounds of A m Mn II n (CN) m+2n stoichiometry. Here, the creation and characterization of this large family of compounds, for example AMn II 3 (CN) 7 , A 2 Mn II 3 (CN) 8 , A 2 Mn II 5 (CN) 12 , A 3 Mn II 5 (CN) 13 , and A 2 Mn II [Mn II (CN) 6 ], where A represents alkali and tetraalkylammonium cations, is reviewed. Cs 2 Mn II [Mn II (CN) 6 ] has the typical Prussian blue face centered cubic unit cell. However, the other alkali salts are monoclinic or rhombohedral. This is in accord with smaller alkali cation radii creating void space that is minimized by increasing the van der Waals stabilization energy by reducing ∠Mn−N≡C, which, strengthens the magnetic coupling and increases the magnetic ordering temperatures. This is attributed to the non‐rigidity of the framework structure due the significant ionic character associated with the high‐spin Mn II sites. For larger tetraalkylammonium cations, the high‐spin Mn sites lack sufficient electrostatic A + ⋅⋅⋅NC stabilization and form unexpected 4‐ and 5‐coordinated Mn sites within a flexible, extended framework around the cation; hence, the size, shape, and charge of the cation dictate the unprecedented stoichio‐metry and unpredictable cation adaptive structures. Antiferromagnetic coupling between adjacent Mn II sites leads to ferrimagnetic ordering, but in some cases antiferromagnetic coupling of ferrimagnetic layers are compensated and synthetic antiferromagnets are observed. The magnetic ordering temperatures for ferrimagnetic A 2 Mn II [Mn II (CN) 6 ] with both octahedral high‐ and low‐spin Mn II sites increase with decreasing ∠Mn−N≡C. The crystal structures for all of the extended structured materials were obtained by powder diffraction.

Chemistry↗
DOE OSTI2023

Remote and automated high-throughput powder diffraction measurements enabled by a robotic sample changer at SSRL beamline 2-1

The general-purpose powder diffractometer beamline (BL2-1) at the Stanford Synchrotron Radiation Lightsource (SSRL) is described. The evolution of design and performance of BL2-1 are presented, in addition to current operating specifications, applications and measurement capabilities. Recent developments involve a robotic sample changer enabling high-throughput X-ray diffraction measurements, applicable to mail-in and remote operations. In situ and operando capabilities to measure samples with different form factors ( e.g. capillary, flat plate or thin film, and transmission) and under variable experimental conditions are discussed. Several example datasets and accompanying Rietveld refinements are presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Neutron powder diffraction, Mossbauer Spectroscopy and Optical Spectroscopy to study magnetic and nuclear lattices in Fe-based oxychlorides Ca2FeO3Cl, Sr2FeO3Cl and Sr3Fe2O5Cl2

Data for Neutron Diffraction, Mossbauer Spectoscopy and Optical Spectroscopy are contained on all three samples (Ca2FeO3Cl, Sr2FeO3Cl, and Sr3Fe2O5Cl2). Mossbauer data are in the folder "MossbauerSpectroscopy". This contains details of files and examples to read the data. The Optical Spectroscopy are in the folder "AbsorptionData", this contains one file with explanatory headers. The neutron diffraction data are in the "NeutronDiffractionData" folder. The data was collected on the HB-2A powder diffractometer at HFIR. The autoreduced files are corrected using a vanadium standard and are in arbitrary intensity units. The RawData folder contains the uncorrected data with metadata for motor positions and temperature. All measurements were collected with a constant neuton wavelength of 2.41 Angstrom. An excel spreadsheet "NeutronDiffractionData_IPTS-29118_summary" contains details for each scan. Sr3Fe2O5Cl2 data were collected at only room temperature. Ca2FeO3Cl and Sr2FeO3Cl data were collected at 4K and room temperature. The autoreduced .dat fileformat is three columns corresponding to: Two-theta, Intensity and Intensity_error.

fe-based oxychlorides↗
DOE OSTI2024

Tuning the spontaneous exchange bias effect in La 1.5 Sr 0.5 CoMnO 6 with sintering temperature

Here, in this study, we present a study of the influence of microstructure on the magnetic properties of polycrystalline samples of the La 1.5 Sr 0.5 CoMnO 6 double perovskite, with primary attention to the spontaneous exchange bias effect, a fascinating recently discovered phenomena for which some materials exhibit unidirectional magnetic anisotropy after being cooled in zero magnetic fields. By sintering La 1.5 Sr 0.5 CoMnO 6 at different temperatures, we obtained samples with distinct average grain sizes, ranging from 1.54-6.65 μm. A detailed investigation of the material's structural, morphologic, electronic, and magnetic properties using x-ray powder diffraction, powder neutron diffraction, x-ray absorption near edge structure spectroscopy, scanning electron microscopy, and ac and dc magnetometry has revealed a systematic enhancement of the exchange bias effect with increasing the average grain size. This evolution is discussed in terms of changes in the material's porosity and grain morphology and its influence on the exchange couplings at the magnetic interfaces.

14 SOLAR ENERGY↗
DOE OSTI2026

Dara: Automated Multiple-Hypothesis Phase Identification and Refinement from Powder X-ray Diffraction

Powder X-ray diffraction (XRD) is a foundational technique for characterizing crystalline materials. However, the reliable interpretation of XRD patterns, particularly in multiphase systems, remains a manual and expertise-demanding task. As a characterization method that only provides structural information, multiple reference phases can often be fit to a single pattern, leading to potential misinterpretation when alternative solutions are overlooked. To ease humans’ efforts and address the challenge, we introduce Dara (data-driven automated Rietveld analysis), a framework designed to automate the robust identification and refinement of multiple phases from powder XRD data. Dara performs an exhaustive tree search over all plausible phase combinations within a given chemical space and validates each hypothesis using the BGMN Rietveld refinement routine. Key features include structural database filtering, automatic clustering of isostructural phases during tree expansion, and peak-matching-based scoring to identify promising phases for refinement. When ambiguity exists, Dara generates multiple hypothesis which can then be decided between by human experts or with further characterization tools. By enhancing the reliability and accuracy of phase identification, Dara enables scalable analysis of realistic complex XRD patterns and provides a foundation for integration into multimodal characterization workflows, moving toward fully self-driving materials discovery.

Biological databases↗
DOE OSTI2025

Structural Distortions and Uniaxial Negative Thermal Expansion in the Polar Dion–Jacobson Oxide RbNdTa 2 O 7

We provide deeper insight into the crystal structures, sequential structural phase transitions (I2cm → Cmce → I4/mcm → P4/mmm), thermal expansion, and electronic properties of the n = 2 Dion–Jacobson polar oxide RbNdTa 2 O 7 , through X-ray powder diffraction, neutron powder diffraction, Raman studies, and density functional theory calculations. We observed a uniaxial negative thermal expansion (NTE) across the first-order transition, I2cm → Cmce, where the unit cell contracts along the c-axis, which is driven by a contraction of the NdTa 2 O 6 layer. Here, this NTE occurs within the temperature range of the first-order phase transition and contrasts with the corkscrew mechanism typically observed in Ruddlesden–Popper phases. In RbNdTa 2 O 7 , the I2cm (hybrid improper ferroelectric) → Cmce (antipolar) transition involves crucial changes in the bond lengths of Nd and Ta polyhedra, coupled with polar to antipolar displacement of the Nd ions, leading to a net contraction in the NdTa 2 O 6 layer along the c-axis, while preserving the overall octahedral tilting magnitude. This transition highlights the intricate interplay between the Nd and Ta coordination and the associated TaO 6 distortions. Temperature-dependent Raman spectra analysis further confirms the first-order structural transition and associated NTE, providing evidence for increased bond stiffness across this transition. Additionally, using neutron powder diffraction, we have determined that the transition I4/mcm → P4/mmm occurs at approximately 1150 K. Finally, we have calculated from DFT + U, the partial density of states, the energy bandgaps, and effective masses of the charge carriers of the polar ground structure.

Chemical structure↗
DOE OSTI2025

Investigating Quantum Materials with Half-Polarized Diffraction and magnetic PDF analysis at the HB-2A Neutron Powder Diffractometer

Local magnetic ordering and anisotropy is often central to the emergent behavior and subsequent functional properties in quantum materials and beyond. Neutron powder diffraction provides a straightforward yet extremely powerful technique for quantitative measurements of microscopic magnetic properties. The HB-2A powder diffractometer located at the High Flux Isotope Reactor in ORNL is traditionally utilized for long-range magnetic structure determination. Recently these capabilities have been extended to include methods aimed at accessing local magnetism: Half- polarized neutron powder diffraction (pNPD) and magnetic pair distribution function (mPDF) analysis. These two distinct techniques are possible on HB-2A due to the versatility of the instrument’s reciprocal space coverage, resolution and novel ultra-low temperature multi-sample changers that operate down to dilution refrigerator temperatures. This provides unique capabilities not found on any powder diffraction instrument and is particularly well suited to investigations of magnetic quantum materials. The development and implementation of these techniques will be discussed with a series of science case examples ranging from geometric frustrated magnets to magnetic metal-organic frameworks. Data reduction and analysis tools will be presented that enable the extraction of the local site susceptibility tensor and local spin-spin correlations in real space. Finally, potential combinations of these techniques in the form of half-polarized magnetic pair distribution function (pmPDF) analysis will be considered. Looking forward, HB-2A is undergoing a detector upgrade that will be in the user program by 2026. This will offer an order of magnitude increase in count rates to further aid the development of these often low signal measurements and provide new scientific capabilities.

Neutron Scattering↗
DOE OSTI2025

Crystal structure of Cu2Zn(GexSi1−x)Se4 solid solution: the kesterite to wurtz–kesterite structural phase transition

Developing low-cost, sustainable, and environmentally friendly top absorber layers for tandem solar cells is essential to advancing photovoltaic technologies and accelerating the transition to renewable energy. In this work, we explore the potential of tetravalent (Cu2Zn(GexSi1−x)Se4) cation mutations in chalcogenide compound semiconductors with the aim of finding a material with increased band gap and reduced structural disorder. A combination of high-resolution synchrotron powder diffraction and neutron powder diffraction was used to determine the atomic positions and monoclinic angles in monoclinic wurtz–kesterite type Cu2Zn(GexSi1−x)Se4 mixed crystals as well as to determine the cation distribution in the crystal structure of Ge-rich kesterite-type and Si-rich wurtz–kesterite type mixed crystals. These investigations enabled us to deduce the structural transition scenario within the Cu2Zn(GexSi1−x)Se4 series. The transition occurs via a region where two phases with different crystal structures, tetragonal and monoclinic and thus a different distortion of the coordination tetrahedra, but the same cation distribution within the element specific cation sites co-exist. Thus, the structural transition between the kesterite and the wurtz–kesterite structure within the Cu2Zn(GexSi1−x)Se4 series is a distortion driven transition. The study identifies cation mutation in quaternary chalcogenides as a promising strategy beyond chalcopyrites and kesterites for low cost and environmentally friendly top absorbers in tandem solar cells.

Gurieva, Galina [Helmholtz Center Berlin for Mater↗
DOE OSTI2025

Temperature-Dependent Structural Transition in Cu-Intercalated Trigonal CuYbSe 2

Rare-earth delafossites, ARCh 2 ; A = alkali metal, R = rare-earth, Ch = chalcogen which consist of intercalated rare-earth metal dichalcogenides, host frustrated triangular lattices that are fertile ground for exotic phenomena. In most cases, the triangular rare-earth sublattice arises from R-3m (No. 166) structures with three layers of rare-earth metal dichalcogenide octahedra or P6 3 /mmc (No. 194) structures with two such layers, analogous to those found in transition metal dichalcogenides. Substituting the alkali metal with Cu + yields a distinct trigonal crystal symmetry P-3m1 (No. 164) in these structures. This symmetry change alters the coordination environment from ASe 6 octahedra in R-3m AYbSe 2 to CuSe 4 tetrahedra in CuYbSe 2 , resulting in shortened rare-earth to rare-earth separations and significantly reduced interlayer distances. Using X-ray single-crystal diffraction, powder neutron diffraction, resistance, and specific heat measurements, a structural transition slightly below room temperature (258 K) is observed. The low-temperature structure is a lower-symmetry I2/m structure, accompanied by partial Cu-site vacancy ordering. The combination of Cu disorder and the triangular lattice geometry in CuYbSe 2 provides a promising platform for investigating frustrated magnetism and unconventional transport phenomena.

Chemical structure↗