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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Protonation Stimulates the Layered to Rock Salt Phase Transition of Ni‐Rich Sodium Cathodes

Abstract Protonation of oxide cathodes triggers surface transition metal dissolution and accelerates the performance degradation of Li‐ion batteries. While strategies are developed to improve cathode material surface stability, little is known about the effects of protonation on bulk phase transitions in these cathode materials or their sodium‐ion battery counterparts. Here, using NaNiO 2 in electrolytes with different proton‐generating levels as model systems, a holistic picture of the effect of incorporated protons is presented. Protonation of lattice oxygens stimulate transition metal migration to the alkaline layer and accelerates layered‐rock‐salt phase transition, which leads to bulk structure disintegration and anisotropic surface reconstruction layers formation. A cathode that undergoes severe protonation reactions attains a porous architecture corresponding to its multifold performance fade. This work reveals that interactions between electrolyte and cathode that result in protonation can dominate the structural reversibility/stability of bulk cathodes, and the insight sheds light for the development of future batteries.

25 ENERGY STORAGE↗
DOE OSTI2025

Unraveling emission line galaxy conformity at z ∼ 1 with DESI early data

Emission line galaxies (ELGs) are now the preeminent tracers of large-scale structure at z > 0.8 due to their high density and strong emission lines, which enable accurate redshift measurements. However, relatively little is known about ELG evolution and the ELG–halo connection, exposing us to potential modelling systematics in cosmology inference using these sources. In this paper, we use a variety of observations and simulated galaxy models to propose a physical picture of ELGs and improve ELG–halo connection modelling in a halo occupation distribution framework. We investigate Dark Energy Spectroscopic Instrument (DESI)-selected ELGs in COSMOS data, and infer that ELGs are rapidly star-forming galaxies with a large fraction exhibiting disturbed morphology, implying that many of them are likely to be merger-driven starbursts. We further postulate that the tidal interactions from mergers lead to correlated star formation in central–satellite ELG pairs, a phenomenon dubbed ‘conformity’. We argue for the need to include conformity in the ELG–halo connection using galaxy models such as IllustrisTNG, and by combining observations such as the DESI ELG autocorrelation, ELG cross-correlation with luminous red galaxies, and ELG–cluster cross-correlation. We also explore the origin of conformity using the UniverseMachine model and elucidate the difference between conformity and the well-known galaxy assembly bias effect.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Neutrino physics beyond the current paradigm

An exciting program of international neutrino experiments aims to complete our understanding of three-neutrino mixing in the Standard Model (SM), which has had great success in describing world neutrino data. However, there exist a number of short-baseline neutrino anomalies that do not fit into this simple picture and could be pointing us instead to phenomena beyond the Standard Model (BSM). Neutrinos and neutrino experiments are excellent laboratories to search for BSM physics for a number a reasons. First, neutrinos mass itself is evidence of BSM physics as it implies the addition of new fields to the SM. In addition, neutrino properties are not well-constrained and allow sizable, new interactions. Finally, accelerator- and reactor-based short-baseline neutrino experiments bring high luminosity sources of photons, nuclear, and meson decays near large, sensitive detectors and can therefore probe a variety of dark sector models. In this talk, I will give an overview of worldwide accelerator- and reactor-based short-baseline neutrino experiments and their efforts to search for physics beyond the current paradigm.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

A structural explanation for the mechanism and specificity of plant branching enzymes I and IIb

Branching enzymes (BEs) are essential in the biosynthesis of starch and glycogen and play critical roles in determining the fine structure of these polymers. The substrates of these BEs are long carbohydrate chains that interact with these enzymes via multiple binding sites on the enzyme’s surface. By controlling the branched-chain length distribution, BEs can mediate the physiological properties of starch and glycogen moieties; however, the mechanism and structural determinants of this specificity remain mysterious. In this study, we identify a large dodecaose binding surface on rice BE I (BEI) that reaches from the outside of the active site to the active site of the enzyme. Mutagenesis activity assays confirm the importance of this binding site in enzyme catalysis, from which we conclude that it is likely the acceptor chain binding site. Comparison of the structures of BE from Cyanothece and BE1 from rice allowed us to model the location of the donor-binding site. We also identified two loops that likely interact with the donor chain and whose sequences diverge between plant BE1, which tends to transfer longer chains, and BEIIb, which transfers exclusively much shorter chains. When the sequences of these loops were swapped with the BEIIb sequence, rice BE1 also became a short-chain transferring enzyme, demonstrating the key role these loops play in specificity. Taken together, these results provide a more complete picture of the structure, selectivity, and activity of BEs.

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

Phase-Space Geometry and Optimal State Preparation in Quantum Metrology with Collective Spins

We revisit well-known protocols in quantum metrology using collective spins and propose a unifying picture for optimal state preparation based on a semiclassical description in phase space. We show how this framework allows for quantitative predictions of the timescales required to prepare various metrologically useful states, and that these predictions remain accurate even for moderate system sizes, surprisingly far from the classical limit. Furthermore, this framework allows us to build a geometric picture that relates optimal (exponentially fast) entangled probe preparation to the existence of separatrices connecting saddle points in phase space. We illustrate our results with the paradigmatic examples of the two-axis countertwisting and twisting-and-turning Hamiltonians, where we provide analytical expressions for all the relevant optimal timescales. Finally, we propose a generalization of these models to include p-body collective interaction (or p-order twisting), beyond the usual case of p = 2. Using our geometric framework, we prove a no-go theorem for the local optimality of these models for p > 2.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Multistep Coulomb excitation of Ni 64 : Shape coexistence and nature of low-spin excitations

Here, the structure of 64 Ni, the heaviest stable Ni isotope, has been investigated via high-statistics, multistep safe Coulomb excitation to search for shape coexistence, a phenomenon recently observed in neutron-rich 66 Ni and 70 Ni as well as in doubly magic, N = 40, 68 Ni. The study was motivated by recent, state-of-the-art Monte Carlo shell-model calculations (MCSM), where a Hamiltonian with effective interactions incorporating the monopole tensor force predicts the existence of shape coexistence, also in the lower-mass 62,64 Ni isotopes. A set of transition and static E2 matrix elements for both yrast and near-yrast structures was extracted from the differential Coulomb excitation cross sections. From comparisons between the new results and MCSM as well as other shell-model calculations, a clearer picture of the structure of 64 Ni emerges. Specifically, the low-spin states are shown to be dominated by proton and neutron excitations mainly within the fp shell, with minimal contribution from the g 9/2 shape-driving neutron orbital. The agreement between experimental data and MCSM results indicates a small oblate deformation for the $0$$^{+}_{2}$ level and a spherical shape for the $0$$^{+}_{3}$ state. In addition, the small upper limit determined for the B(E2) probability of a transition associated with the decay of the recently observed 3463-keV, $0$$^{+}_{4}$ state agrees with its proposed assignment to a prolate shape, herewith providing first evidence for triple shape coexistence in a stable Ni isotope.

59 ≤ A ≤ 89↗
DOE OSTI2021

Nuclear Transparency from Quasi-elastic ¹²C(e, e'p) scattering reaction up to Q2 = 14.2 (GeV/c)2 in Hall C at Jefferson Lab

Color Transparency (CT) is a unique prediction of Quantum Chromodynamics (QCD) where the final (and/or initial) state interactions of hadrons with the nuclear medium are suppressed for exclusive processes at high momentum transfers. While this phenomenon has been observed for mesons, there has never been a conclusive observation for baryons. A clear signal of CT for baryons would be the first evidence of baryons fluctuating to a small size in the nucleus, and the onset would show the transition from nucleon-meson picture to quark-gluon degrees of freedom. The experiment E1206107, searching for the onset of CT in protons was completed in Hall C at Jefferson Laboratory (JLab) using the upgraded 12 GeV e- beam. It used the High Momentum Spectrometer (HMS) and the new Super High Momentum spectrometer (SHMS) in coincidence to measure the e- + ¹²C ? e-' + p + X reaction in quasi-elastic kinematics. Data were collected on a ¹²C target over the range of Q2 = 8 - 14.3 (GeV/c)2, covering the region where a previous p + A ? p' + p + X experiment at Brookhaven National Laboratory (BNL) had observed an enhancement. Proton Transparency (PT) was extracted from these data. A rise in the PT as a function of Q2 (defined as the square of the negative of the 4-momentum transfer by the scattered electron) is predicted to be a signature of the onset of CT. Our data showed no significant increase and consistent with the traditional nuclear physics calculation. This dissertation discusses the theory and implementation of the CT experiment, summarizes the data analysis and presents results on hydrogen normalization and nuclear transparency.

Bhetuwal, Deepak↗
DOE OSTI2024

Capturing Surface Coverage Effects in Heterogeneous Catalysis

Adsorbate–adsorbate lateral interactions at relevant surface coverages have a significant effect on chemical kinetics, thereby influencing the activity of a heterogeneous catalyst. Coverage-dependent kinetic and thermodynamic parameters therefore must be included in studies of such complex systems to properly predict the turnover frequencies and kinetic trends. Thus, it becomes extremely important to accurately capture the strength of lateral interactions between neighboring species under realistic reaction conditions. In this Perspective, we discuss the various existing computational and experimental methods for determining adspecies coverage and configurational effects. The choice of the tools and methods employed in such studies depends on factors such as time, length scales, computational cost, the presence of solvents, and reaction conditions. The applications of each method and the respective challenges are also discussed here. As a result, we discuss the recent developments and future of the state-of-the-art for inclusion of surface coverage and configuration into a holistic picture for accurate predictions of catalytic behavior.

09 BIOMASS FUELS↗
DOE OSTI2024

Exciton–Phonon Coupling Induces a New Pathway for Ultrafast Intralayer-to-Interlayer Exciton Transition and Interlayer Charge Transfer in WS 2 –MoS 2 Heterostructure: A First-Principles Study

Despite the weak, van der Waals interlayer coupling, photoinduced charge transfer vertically across atomically thin interfaces can occur within surprisingly fast, sub-50 fs time scales. An early theoretical understanding of charge transfer is based on a noninteracting picture, neglecting excitonic effects that dominate optical properties of such materials. We employ an ab initio many-body perturbation theory approach, which explicitly accounts for the excitons and phonons in the heterostructure. Our large-scale first-principles calculations directly probe the role of exciton-phonon coupling in the charge dynamics of the WS 2 /MoS 2 heterobilayer. We find that the exciton-phonon interaction induced relaxation time of photoexcited excitons at the K valley of MoS 2 and WS 2 is 67 and 15 fs at 300 K, respectively, which sets a lower bound to the intralayer-to-interlayer exciton transfer time and is consistent with experiment reports. We further show that electron-hole correlations facilitate novel transfer pathways that are otherwise inaccessible to noninteracting electrons and holes.

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

How to identify different new neutrino oscillation physics scenarios at DUNE

Next generation neutrino oscillation experiments are expected to measure the remaining oscillation parameters with very good precision. They will have unprecedented capabilities to search for new physics that modify oscillations. DUNE, with its broad band beam, good particle identification, and relatively high energies will provide an excellent environment to search for new physics. If deviations from the standard three-flavor oscillation picture are seen however, it is crucial to know which new physics scenario is found so that it can be verified elsewhere and theoretically understood. We investigate several benchmark new physics scenarios by looking at existing long-baseline accelerator neutrino data from NOvA and T2K and determine at what sensitivity DUNE can differentiate among them. We consider sterile neutrinos and both vector and scalar non-standard neutrino interactions, all with new complex phases, the latter of which could conceivably provide absolute neutrino mass scale information. We find that, in many interesting cases, DUNE will have good model discrimination. We also perform a new fit to NOvA and T2K data with scalar NSI.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Self-Assembled Oligomers Facilitate Amino Acid-Driven CO 2 Capture at the Air–Aqueous Interface

Direct air capture of CO 2 using amino acid absorbents, such as glycine or sarcosine, is constrained by the relatively slow mass transfer of CO 2 through the air–aqueous interface. Our recent study showed a marked improvement in CO 2 capture by introducing CO 2 -permeable oligo-dimethylsiloxane (ODMS-MIM + ) oligomers with cationic (imidazolium, MIM + ) headgroups. Here, in this work, we have employed all-atom molecular dynamics simulations in combination with subensemble analysis using network theory to provide a detailed molecular picture of the behavior of CO 2 and the glycinate anions (Gly – ) at the ODMS-MIM + decorated air–aqueous interfaces. We show that the cationic head groups of the surfactants enhance the concentration and lifetime of Gly – in the interfacial region, while ODMS tails promote the physisorption of CO 2 in the interfacial region. Together, these two factors increase the effective region of contact and the probability of interactions between CO 2 and Gly – compared to that of the pure air–aqueous interface. The fundamental insights gained in this work establish essential foundations for developing hybrid systems with oligomer-decorated interfaces to maximize the overall CO 2 capture rates.

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

Quantum oscillation of thermally activated conductivity in a monolayer WTe 2 -like excitonic insulator

Recently, quantum oscillation of the resistance in insulating monolayer WTe 2 was reported. An explanation in terms of gap modulation in the hybridized Landau levels of an excitonic insulator was also proposed by one of us. However, the previous picture of gap modulation in the Landau levels spectrum was built on a pair of well nested electron and hole Fermi surfaces, while the monolayer WTe 2 has one hole and two electron Fermi pockets with relative anisotropy. In this work we demonstrate that for system like monolayer WTe 2 , the excitonic insulating state arising from the coupled one hole and two electron pockets possesses a finite region in interaction parameter space that shows gap modulation in a magnetic field. In this region, the thermally activated conductivity displays the 1/B periodic oscillation and it can further develop into discrete peaks at low temperature, in agreement with the experimental observation. We show that the relative anisotropy of the bands is a key parameter and the quantum oscillations decrease rapidly if the anisotropy increases further than the realistic value for monolayer WTe 2 .

2-dimensional systems↗
DOE OSTI2023

Minimal one-dimensional model of bad metal behavior from fast particle-hole scattering

A strongly interacting plasma of linearly dispersing electron and hole excitations in two spatial dimensions (2D), also known as a Dirac fluid, can be captured by relativistic hydrodynamics and shares many universal features with other quantum critical systems. Here, we propose a one-dimensional (1D) model to capture key aspects of the 2D Dirac fluid while including lattice effects and being amenable to nonperturbative computation. When interactions are added to the Dirac-like 1D dispersion without opening a gap, we show that this kind of irrelevant interaction is able to preserve Fermi-liquid-like quasiparticle features while relaxing a zero-momentum charge current via collisions between particle-hole excitations, leading to resistivity that is linear in temperature via a mechanism previously discussed for large-diameter metallic carbon nanotubes. We further provide a microscopic lattice model and obtain numerical results via density-matrix renormalization group simulations, which support the above physical picture. The limits on such fast relaxation at strong coupling are of considerable interest because of the ubiquity of bad metals in experiments.

1-dimensional systems↗
DOE OSTI2024

A Picture is Worth a Thousand Data Points: Introduction to Visualization

They say a picture is worth a thousand words. My response to that? A picture is also worth a thousand data points! However, not all pictures are created equal: a good visualization tells a story and helps the viewer to understand the data. A polished visualization can help you In the first half of this workshop, I will discuss the seven sins of visualization, and how to avoid them. I will introduce guidelines on how to make excellent visualization choices. In the second half of the workshop, I will guide the participants in an interactive session on creating meaningful visualizations with just a few lines of code.

code↗
DOE OSTI2022

The importance of localized modes spectral contribution to thermal conductivity in amorphous polymers

Abstract Polymers are a unique class of materials from the perspective of normal mode analysis. Polymers consist of individual chains with repeating units and strong intra-chain covalent bonds, and amorphous arrangements among chains with weak inter-chain van der Waals and for some polymers also electrostatic interactions. Intuitively, this strong heterogeneity in bond strength can give rise to special features in the constituent phonons, but such effects have not been studied deeply before. Here, we use lattice dynamics and molecular dynamics to perform modal analysis of the thermal conductivity in amorphous polymers. We find an abnormally large population of localized modes in amorphous polymers, which is fundamentally different from amorphous inorganic materials. Contrary to the common picture of thermal transport, localized modes in amorphous polymers are found to be the dominant contributors to thermal conductivity. We find that a significant portion of the localization happens within individual chains, but heat is dominantly conducted when localized modes involve two chains. These results suggest localized modes generally play a key role in thermal transport for different polymers. The results provide an alternative perspective on why polymer thermal conductivity is generally quite low and gives insight into how to potentially change it.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Doped NiO: The mottness of a charge transfer insulator

The evolution of the electronic structures of strongly correlated insulators with doping has long been a central fundamental question in condensed matter physics; it is also of great practical relevance for applications. We have studied the evolution of NiO under hole and electron doping at low doping levels such that the system remains insulating using high-quality thin film and a wide range of experimental and theoretical methods. The evolution is in both cases very smooth with dopant concentration. The band gap is asymmetric under electron and hole doping, consistent with a charge-transfer insulator picture, and is reduced faster under hole doping than under electron doping. For both electron and hole doping, occupied states are introduced at the top of the valence band. The formation of deep donor levels under electron doping and the inability to pin otherwise empty states near the conduction-band edge are indicative that local electron addition and removal energies are dominated by a Mott-like Hubbard U interaction even though the global band gap is predominantly a charge-transfer-type gap.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Tomographic imaging of atmospheric pressure plasma on complex surfaces

Many plasma types and behaviors such as streamer, arcs, cathode spots, anode spots, ionization waves, and magnetic field interactions create non-symmetric, fully 3D plasma structures. The plasma distribution in 3D space is heavily influenced by complex surfaces and the coupling interactions between plasma properties and the interfacing material properties. For example, ionization waves propagate in directions where ionization rates are highest, leading to complex configurations that are not fully understood or well characterized. Recent advances in laser diagnostics and models have been able to investigate well-controlled idealized plasmas in 2D fashion, but the complex structure in actual plasmas requires a technique than can provide a more complete 3D picture. However, 3D plasma diagnostics do not currently exist. To address this limitation, this activity will leverage available equipment to build a new tomographic optical imaging capability and advance the state-of-the-art in plasma diagnostics to investigate 3D phenomena on complex surfaces.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗