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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Probing the Isospin Composition of Short-Range Correlated Pairs at Jefferson Lab Hall B

Nucleons in short-range correlated (SRC) pairs, due to their close proximity and high relative momentum, can provide insight into the short-range part of the strong nuclear interaction. In particular, the prevalence of np pairs is due to the dominance of a tensor term for correlated nucleons with momenta of approximately 400?600 MeV/c. This dissertation comprises two studies advancing the community?s understanding of the isospin composition of SRC pairs. First, I performed a study of proton and neutron knockout from initially low-momentum and high-momentum states in 3He. Previous work has shown that protons are disproportionately represented in high-momentum states in neutron-rich nuclei. I demonstrate that spectral functions for the proton-rich nucleus 3He predict, in agreement with data, that neutrons are disproportionately represented in high-momentum states, but that 3He does not display the same strong prevalence of np pairs that is observed in larger nuclei. Second, Generalized Contact Formalism (GCF), a well-supported theory for predicting SRC behavior, predicts the transition from an isospin-dependent, tensor-dominant interaction at intermediate distances to a scalar-dominant, isospin-independent interaction at very short distances. This dissertation uses data from the CLAS12 Nuclear Targets Experiments in Hall B at Jefferson Lab to measure the relative abundances of pp and pn pairs for increasing relative momentum and decreasing separation. I provide an independent confirmation of the previously-observed increase in pp pairs at increasing momentum of the struck nucleon. I also contribute to the application of the new CLAS12 Central Neutron Detector by precisely measuring the neutron detection efficiency and developing a machine learning model for rejecting charged particle background.

Seroka, Erin↗
DOE OSTI2024

First-principles and cluster expansion study of the effect of magnetism on short-range order in Fe–Ni–Cr austenitic stainless steels

Short-range order (SRO), the regular and predictable arrangement of atoms over short distances, alters the mechanical properties of technologically relevant structural materials such as medium/high entropy alloys and austenitic stainless steels. In this study, we present a generalized spin cluster expansion (CE) model and show that magnetism is a primary factor influencing the level of SRO present in austenitic Fe-Ni-Cr alloys. The spin CE consists of a chemical cluster expansion combined with an Ising model for Fe-Ni-Cr austenitic alloys. It explicitly accounts for local magnetic exchange interactions, thereby capturing the effects of finite temperature magnetism on SRO. Model parameters are obtained by fitting to a first-principles data set comprising both chemically and magnetically diverse FCC configurations. The magnitude of the magnetic exchange interactions are found to be comparable to the chemical interactions. Compared to a conventional implicit magnetism CE built from only magnetic ground state configurations, the spin CE shows improved performance on several experimental benchmarks over a broad spectrum of compositions, particularly at higher temperatures due to the explicit treatment of magnetic disorder. We find that SRO is strongly influenced by alloy Cr content, since Cr atoms prefer to align antiferromagnetically with nearest neighbors but become magnetically frustrated with increasing Cr concentration. Using the spin CE, we predict that increasing the Cr concentration in typical austenitic stainless steels promotes the formation of SRO and increases order-disorder transition temperatures. Furthermore, this study underscores the significance of considering magnetic interactions explicitly when exploring the thermodynamic properties of complex transition metal alloys. It also highlights guidelines for customizing SRO through adjustments of alloy composition.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Rigorous computation of short-range order unifies its controversial effects in complex concentrated alloys

Direct experimental observations of chemical short-range order (SRO) in complex concentrated alloys (CCAs) have triggered high interest. However, the reported effects of SRO on yield stresses are controversial, and their atomic-scale mechanisms are elusive, which limits our ability to utilize SRO in alloy design. Here we tackle this challenge using an advanced computational approach that rigorously takes into account the critical lattice distortion in CCAs and further verify our theoretical predictions with experiments. We show that the CoCrNi model alloy has a narrow temperature window around 670 °C for SRO formation. This explains why the mechanical effect of SRO is observed in some experiments but not in others. Here, we propose an effective alloy-doping method to control SRO and reveal atomic-bonding types that dominate SRO formation for different alloys. The strategies and insights generally apply to a broad spectrum of alloys, laying the foundation for designing advanced alloys by manipulating their SRO.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Measuring short-range correlations and quasi-elastic cross sections in A(e,e’) at x > 1 and modest Q 2

We present results from the Jefferson Lab E08-014 experiment, investigating short-range correlations (SRC) through measurements of inclusive quasi-elastic scattering from 2 H, 3 He, 4 He, 12 C, 40 Ca, and 48 Ca. The kinematics were selected to isolate scattering from SRCs, yielding a plateau in the A/ 2 H cross-section ratios due to the universal two-body structure of the 2N-SRCs in light and heavy nuclei. We observe approximate plateaus in the A/ 2 H ratios and provide the first extractions of the A/ 2 H ratio for 40 Ca and 48 Ca. We also examine the A/ 3 He ratio, aiming to identify three-nucleon SRCs (3N-SRCs). Following the approach for isolating 2N-SRCs, searching for 3N-SRC dominance involved measuring the A/ 3 He cross section ratio at modest-to-large Q 2 values and looking for a plateau ratios for x ≳ 2.5. This was not observed in the data, and in fact increasing Q 2 values moved the data further away from the predicted plateau. We show here that, when analyzed in terms of the struck nucleon’s light-cone momentum, the data exhibited the expected trend, progressively approaching the predicted 3N-SRC plateau. These observations suggest that future measurements at higher energies may facilitate a definitive isolation and identification of 3N-SRCs.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Synthesis and Self-Assembly of Monodisperse Graphene Nanoribbons: Access to Submicron Architectures with Long-Range Order and Uniform Orientation

Fabricating organic semiconducting materials into large-scale well-organized architectures is critical for building high performance molecular electronics. While graphene nanoribbons (GNRs) hold enormous promise for various device applications, their assembly into a well-structured monolayer or multilayer architecture poses a substantial challenge. Here we report the preparation of length-defined monodisperse GNRs via the integrated iterative binomial synthesis (IIBS) strategy and their self-assembly into submicron-architectures with long-range order, uniform orientation as well as regular layers. Further, the use of short alkyl side chains benefits forming stable multi-layers through interlocking structures. By changing the length and backbone shapes of these monodisperse GNRs, various three-dimensional assemblies including multilayer stripes, monolayer stripes, and nanowires, can be achieved, leading to different photophysical properties and band gaps. The discovery of these intriguing self-assembly behaviors of length-defined GNRs is expected to open the door for various future applications.

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

Long-Range Resonant Charge Transport through Open-Shell Donor–Acceptor Macromolecules

A grand challenge in molecular electronics is the development of molecular materials that can facilitate efficient longrange charge transport. Research spanning more than two decades has been fueled by the prospects of creating a new generation of miniaturized electronic technologies based on molecules whose synthetic tunability offers tailored electronic properties and functions unattainable with conventional electronic materials. However, current design paradigms produce molecules that exhibit off-resonant transport under low bias, which limits the conductance of molecular materials to unsatisfactorily low levels several orders of magnitude below the conductance quantum 1 G 0 and often results in an exponential decay in conductance with length. Here, we demonstrate a chemically robust, air-stable, and highly tunable molecular wire platform comprised of open-shell donor−acceptor macromolecules that exhibit remarkably high conductance close to 1 G 0 over a length surpassing 20 nm under low bias, with no discernible decay with length. Single-molecule transport measurements and ab initio calculations show that the ultralong-range resonant transport arises from extended π-conjugation, a narrow bandgap, and diradical character, which synergistically enables excellent alignment of frontier molecular orbitals with the electrode Fermi energy. The implementation of this long-sought-after transport regime within molecular materials offers new opportunities for the integration of manifold properties within emerging nanoelectronic technologies.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Kinetic interplay between chemical short-range order and grain boundaries in NiCoCr alloys under irradiation

Chemical short-range order (CSRO) and grain boundary (GB) engineering are routes to enhance radiation damage tolerance in alloys. Here, we reveal that CSRO and GB interact in a sink-strength-dependent manner under irradiation in NiCoCr. Near a weak sink (Σ3 GB), CSRO reduces defect cluster growth by slowing interstitial diffusion and enhancing vacancy-interstitial recombinations. In contrast, near strong sinks such as Σ5 GBs, CSRO and GB act competitively for interstitial accumulation but synergistically to suppress large stacking-fault tetrahedra growth via enhanced recombination. Such mechanistic duality underscores the need for coordinated control of CSRO stability and GB sink strength to enhance radiation damage tolerance.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Harnessing Chemical Short‐Range Disorder to Improve Lithium Retention in Epitaxial LLTO Solid‐Electrolyte Thin Films

Lithium lanthanum titanate Li 3x La 2/3-x TiO 3 (LLTO) is a promising perovskite-based solid-state electrolyte for next-generation lithium-ion batteries, but controlling crystallinity and Li stoichiometry in thin-film form is challenging because high growth temperatures are required to achieve good crystallinity while Li remains strongly volatile. Here, we systematically investigate the effect of substrate temperature on epitaxial LLTO thin films grown by pulsed laser deposition. We identify a narrow growth window (750–800°C) in which LLTO films grow as c-axis oriented with atomically flat surfaces. Lower growth temperatures (<750°C) stabilize laterally extended, chemically disordered stripe domains that coexist with ordered LLTO regions, whereas higher temperatures (≥825°C) suppress these defects but promote island morphologies and Al/Ti interdiffusion. While spectroscopy measurements show that Ti remains in the 4+ oxidation state and Li is globally deficient for all films, our depth-resolved time-of-flight secondary ion mass spectrometry studies reveal that the 700°C film retains the highest Li content across its thickness. These results clarify how growth temperature controls crystallinity, chemical short-range disorder, and Li retention, and highlight moderate growth temperatures (∼700°C) as a route to mitigate Li loss in epitaxial solid-electrolyte films.

chemical short-range disorder↗
DOE OSTI2025

The Juno mission as a probe of long-range new physics

Orbits of celestial objects, especially the geocentric and heliocentric ones, have been well explored to constrain new long-range forces beyond the Standard Model (SM), often referred to as fifth forces. In this paper, for the first time, we apply the motion of a spacecraft around Jupiter to probe fifth forces that don’t violate the equivalence principle. The spacecraft is the Juno orbiter, and ten of its early orbits already allow a precise determination of the Jovian gravitational field. We use the shift in the precession angle as a proxy to test non-gravitational interactions between Juno and Jupiter. Requiring that the contribution from the fifth force does not exceed the uncertainty of the precession shift inferred from data, we find that a new parameter space with the mass of the fifth-force mediator around 10 −14 eV is excluded at 95% C.L.

new light particles↗
DOE OSTI2026

Constraints on long-range forces in de Sitter space

The representation theory of de Sitter space admits partially massless (PM) particles, but whether such particles can participate in consistent interacting theories remains unclear. We investigate the consistency of theories containing PM fields, particularly when these fields are coupled to gravity. Our strategy exploits the fact that PM fields correspond to partially conserved currents on the spacetime boundary, which generate symmetries. These symmetries place stringent constraints on correlation functions of charged operators, allowing us to test the consistency of a proposed bulk spectrum. When the assumed operator content violates these constraints, the corresponding bulk theory is ruled out. Applying this framework, we show that, in four-dimensional de Sitter space, PM fields of spin 2 or 3 (at depth 0) cannot couple consistently to gravity: such couplings necessitate additional massive fields, which are inevitably non-unitary. In higher dimensions, however, the constraints can be satisfied without violating unitarity if further PM fields are included. The resulting structure leads to additional charge conservation laws, which suggests that consistency may ultimately require an infinite tower of higher-spin PM fields, akin to the situation for ordinary higher-spin symmetries. The methods developed here provide powerful constraints on possible long-range interactions in de Sitter space and delineate the landscape of consistent quantum field theories in cosmological spacetimes.

AdS-CFT Correspondence↗
DOE OSTI2025

Evaluating grid stress and reliability in future electricity grids across a range of demand, generation mix, and weather trends

The reliability of power grids in the future will depend on how system planners account for the integration of new technologies, extreme weather events, and uncertainties in demand growth from increased electrification and data centers. This study introduces an open-source, multisectoral, multiscale modeling framework that projects grid stress and reliability trends between 2020 and 2055 in the Western Interconnection of the United States. The framework integrates global to national energy-water-land dynamics with power plant siting and hourly grid operations modeling. We analyze future wholesale electricity price shocks and unserved energy events across eight scenarios spanning a range of population growth and economic change, generation mixes, and weather conditions. Our results show future grids with high percentage of non-renewable generation and strong economic growth are characterized by higher reliability and lower wholesale electricity prices than lower growth scenarios because of larger reliance on dispatchable generators and lower fossil fuel extraction costs. Scenarios with high percentage of renewable resources have lower median but more volatile wholesale electricity prices as well as more frequent and severe unserved energy events compared to scenarios relying more on dispatchable generators. These events occur because higher proportion of solar and wind energy causes net demand curves to deepen during midday (duck curves get progressively severe), exacerbating the challenge of meeting demand during summer evening peaks. This study suggests that robust and co-optimized transmission and energy storage planning could help maintain low wholesale electricity prices and high reliability levels in future electricity grids across uncertainties in generation mixes.

Electric grid reliability↗
DOE OSTI2025

Revisiting a minimally destructive analytic approach for determining electrochemical kinetic parameters: Measuring aluminum corrosion across a wide pH range based on the Butler-Volmer equation

Here, this study revisits the three-point sampling of the simplified Butler-Volmer equation to address the limitations of strong potentiodynamic polarization, which can introduce irreversible damage and uncertainty in corrosion analysis. The method extracts electrochemical kinetic parameters while minimizing polarization effects, evaluates noise sensitivity relative to overpotential, and accounts for errors from signal noise, OCP drift, ohmic resistance, and mass-transfer constraints. Verified against the Tafel extrapolation method for aluminum corrosion across a wide pH range, this low-polarization approach enables accurate evaluations with specific error estimates, offering a robust alternative to linear polarization resistance methods that assume constant Tafel slopes.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Expanding the homogeneity range of UFe 2 : Formation of Laves phase UFe 2 +Ni

Uranium-based intermetallic Laves phases (UM 2 ) provide valuable insight into the interplay of 5f orbital hybridization and magnetic properties. However, ferromagnetism in these compounds is rare. UFe 2 is a cubic C15 Laves phase with greatest Curie temperature (T C ) of all such compounds, at 162 K. In this study, we report the synthesis and characterization of a novel U-based Laves phase, UFe 2 +Ni, effectively forcing excess Ni in to the UFe 2 structure. UFe 2 +Ni crystallizes in the cubic C15 Laves phase, appearing to deviate from the typical UM 2 formula and exhibiting a significantly extended homogeneity range. Annealing this material leads to an increased ferromagnetic transition temperature, between 35 and 155 K, and decreased lattice parameter with higher annealing temperatures. This variation is attributed to changes in Fe and Ni solubility with annealing temperature. In conclusion, our findings highlight the potential for tuning magnetic properties in U-based Laves phases through compositional and thermal modifications, expanding the understanding of magnetically ordered intermetallics.

Annealing effects↗
DOE OSTI2024

A simple model for short-range ordering kinetics in multi-principal element alloys

Short-range ordering (SRO) in multi-principal element alloys influences material properties such as strength and corrosion. While some degree of SRO is expected at equilibrium, predicting the kinetics of its formation is challenging. We present a simplified isothermal concentration-wave (CW) model to estimate an effective relaxation time of SRO formation. Estimates from the CW model agree to within a factor of five with relaxation times obtained from kinetic Monte Carlo (kMC) simulations when above the highest ordering instability temperature. Further, the advantage of the CW model is that it only requires mobility and thermodynamic parameters, which are readily obtained from alloy mobility databases and Metropolis Monte Carlo simulations, respectively. The simple parameterization of the CW model and its analytical nature makes it an attractive tool for the design of processing conditions to promote or suppress SRO in multicomponent alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Nitrogen fixation in Pampinifervens , a new species-rich genus of Aquificaceae that inhabits a wide pH range in terrestrial hot springs

Members of the Aquificota play important roles in hydrogen, sulfur, and carbon cycles in geothermal systems as ubiquitous and abundant chemolithoautotrophs; however, their roles in the nitrogen cycle are poorly defined. Here, we show that Aquificaceae isolate T-2 T from Tengchong, China, fixes nitrogen based on growth with dinitrogen as the sole nitrogen source and incorporation of 15 N atoms when grown with 15 N 2 . We further show evidence that suggests its nitrogen fixation (nif) genes are transcribed in situ in a nearby spring. We propose the name Pampinifervens diazotrophicum gen. et sp. nov., with strain T-2 T (= JCM 35475 T = DSM 116324 T ) as the nomenclatural type. Its close relative designated Pampinifervens florentissimum sp. nov. T-8 T (= CGMC 1.5214 T = JCM 33569 T ) does not fix nitrogen but respires nitrate. Analysis of 104 metagenome-assembled genomes from 84 metagenomes allowed us to circumscribe the genus Pampinifervens and identify at least 16 sympatric Pampinifervens species that dominate the Aquificaceae populations in diverse hot springs in southwest China, with distinct species globally. Analysis of these Pampinifervens genomes revealed variable presence of nif and denitrification genes and frequent gene loss and horizontal transfer. Genes for pH homeostasis were also present in Pampinifervens genomes, with a proliferation in species from Tengchong, consistent with the wide pH growth range of both Pampinifervens isolates and the prevalence of Pampinifervens in both alkaline and acidic springs. The dynamic evolution of nif and denitrification genes, along with pH homeostasis genes, may facilitate the diversification of Pampinifervens into diverse springs with different nitrogen availability.

Aquificae↗
DOE OSTI2024

Medium-Range Structural Order as the Driver of Activated Dynamics and Complexity Reduction in Glass-Forming Liquids

Here, we analyze in depth the Elastically Collective Nonlinear Langevin Equation theory of activated dynamics in metastable liquids to establish that the predicted inter-relationships between the alpha relaxation time, local cage and collective elastic barriers, dynamic localization length, and shear modulus are causally related within the theory to the medium range order (MRO) static correlation length. The latter grows exponentially with density for metastable hard sphere fluids and as a nonuniversal inverse power law with temperature for supercooled liquids under isobaric conditions. The physical origin of predicted connections between the alpha time and other metrics of cage order and the thermodynamic inverse dimensionless compressibility is fully established. It is discovered that although kinetic constraints from the real space first coordination shell are important for the alpha time, they are of secondary importance compared to the consequences of the more universal MRO correlations in both the modestly and deeply metastable regimes. This understanding sheds new light on the theoretical basis for, and prior successes of, the predictive mapping of chemically complex thermal liquids to effective hard sphere fluids based on matching their dimensionless compressibilities, a scheme we call “complexity reduction”. In essence, the latter is equivalent to the physical requirement that the thermal liquid MRO correlation equals that of its effective hard sphere analog. The mapping alone is shown to provide a remarkable level of quantitative predictive power for the glass transition temperature T g of 21 molecular and polymer liquids. Predictions for the chemically specific absolute magnitude and growth with cooling of the MRO correlation length are obtained and lie in the window of 2–6 nm at T g . Dynamic heterogeneity, elastic facilitation, and beyond pair structure issues are briefly discussed. Future opportunities to theoretically analyze the equilibrated deep glass regime are outlined.

cancer↗
DOE OSTI2026

Charge Tethering Drives Intermediate-Range Order and Slow Dynamics in Zwitterionic Liquids

We have synthesized and characterized a family of zwitterionic liquids (ZwLs) based on the poly(ethylene oxide) imidazolium cation and the alkyl sulfonate anion. To better rationalize ZwLs′ structural behavior and networkforming properties, we have computationally studied them in contrast to isostructural but chemically untethered ionic liquid (IL) analogues. Perhaps surprisingly, it is the molecular liquids and not the ILs that show the most selfassembly and intermediate-range order associated with scattering prepeaks; the ZwLs display also the slowest dynamics. This is consistent with prior work showing the importance of networks in considering the viscoelastic relaxation of liquids. We find that, because of their significantly large molecular dipoles, these zwitterions are versatile network-building blocks that result in highly viscous liquids. From a structural perspective, networks in these ZwLs sit somewhere in between what would be true chemical connectivity and the Coulombic networks observed in ionic liquids.

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

Ab Initio Simulation of Medium-Range Ordering in Ionic Glass Electrolytes LiSiPON and LiNaSiPON

Ionic glasses can exhibit a unique combination of optical transparency, electronic resistivity, ionic conductivity, and mechanical ductility. The origin of the relatively high ionic conductivity and ductility is poorly understood. Recently, these ionic glasses were found to have medium-range ordering (MRO) similar to that of metallic glasses. This MRO significantly impacts the properties of metallic glasses and is also expected to significantly impact the properties of ionic glasses. Here, this work used ab initio molecular dynamics (AIMD) simulations to study the effect of ionic glass composition on the MRO. The AIMD models showed that the degree of MRO increased as the temperature of the LiSiPON ionic glass decreased. The modeling also showed that the MRO is suppressed when 50% of Li is substituted with Na. This work lays the foundation for using AIMD to identify clear structure–property relationships in ionic glasses, allowing their properties to be optimized.

Osetsky, Yuri N. [Oak Ridge National Laboratory (O↗