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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Enabling particle applications for exascale computing platforms

The Exascale Computing Project (ECP) is invested in co-design to assure that key applications are ready for exascale computing. Within ECP, the Co-design Center for Particle Applications (CoPA) is addressing challenges faced by particle-based applications across four “sub-motifs”: short-range particle–particle interactions (e.g., those which often dominate molecular dynamics (MD) and smoothed particle hydrodynamics (SPH) methods), long-range particle–particle interactions (e.g., electrostatic MD and gravitational N-body), particle-in-cell (PIC) methods, and linear-scaling electronic structure and quantum molecular dynamics (QMD) algorithms. Our crosscutting co-designed technologies fall into two categories: proxy applications (or “apps”) and libraries. Proxy apps are vehicles used to evaluate the viability of incorporating various types of algorithms, data structures, and architecture-specific optimizations and the associated trade-offs; examples include ExaMiniMD, CabanaMD, CabanaPIC, and ExaSP2. Libraries are modular instantiations that multiple applications can utilize or be built upon; CoPA has developed the Cabana particle library, PROGRESS/BML libraries for QMD, and the SWFFT and fftMPI parallel FFT libraries. Success is measured by identifiable “lessons learned” that are translated either directly into parent production application codes or into libraries, with demonstrated performance and/or productivity improvement. The libraries and their use in CoPA’s ECP application partner codes are also addressed.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2015

Probing long-range carrier-pair spin–spin interactions in a conjugated polymer by detuning of electrically detected spin beating

Here, weakly coupled electron spin pairs that experience weak spin–orbit interaction can control electronic transitions in molecular and solid-state systems. Known to determine radical pair reactions, they have been invoked to explain phenomena ranging from avian magnetoreception to spin-dependent charge-carrier recombination and transport. Spin pairs exhibit persistent spin coherence, allowing minute magnetic fields to perturb spin precession and thus recombination rates and photoreaction yields, giving rise to a range of magneto-optoelectronic effects in devices. Little is known, however, about interparticle magnetic interactions within such pairs. Here we present pulsed electrically detected electron spin resonance experiments on poly(styrene-sulfonate)-doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) devices, which show how interparticle spin–spin interactions (magnetic-dipolar and spin-exchange) between charge-carrier spin pairs can be probed through the detuning of spin-Rabi oscillations. The deviation from uncoupled precession frequencies quantifies both the exchange (<30 neV) and dipolar (23.5±1.5 neV) interaction energies responsible for the pair’s zero-field splitting, implying quantum mechanical entanglement of charge-carrier spins over distances of 2.1±0.1 nm.

36 MATERIALS SCIENCE↗
DOE OSTI2025

$\nu$-Ar Interaction Measurements in the NuMI Beam at ICARUS

This work presents progress toward neutrino-Ar cross-section measurements at ICARUS using the NuMI beam. ICARUS observes muon and electron neutrino interactions in the GeV energy range. Measurements of these interactions offer unique opportunities to infer neutrino interaction cross sections on an argon nuclear target within an energy range that overlaps both the SBN oscillation search and a significant portion of the DUNE spectrum.

Salmoria, Gabrieli [Parana Tech. Fed. U., Toledo] ↗
DOE OSTI2018

Experimental Constraint on an Exotic Spin- and Velocity-Dependent Interaction in the Sub-meV Range of Axion Mass with a Spin-Exchange Relaxation-Free Magnetometer

Here, we conducted a search for an exotic spin- and velocity-dependent interaction for polarized electrons with an experimental approach based on a high-sensitivity spin-exchange relaxation-free (SERF) magnetometer, which serves as both a source of polarized electrons and a magnetic-field sensor. The experiment aims to sensitively detect magnetic-fieldlike effects from the exotic interaction between the polarized electrons in a SERF vapor cell and unpolarized nucleons of a closely located solid-state mass. We report experimental results on the interaction with 82 h of data averaging, which sets an experimental limit on the coupling strength around 10 –19 for the axion mass m a ≲ 10 –3 eV, within the important axion window.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

DARWIN: towards the ultimate dark matter detector

DARk matter WImp search with liquid xenoN (DARWIN) will be an experiment for the direct detection of dark matter using a multi-ton liquid xenon time projection chamber at its core. Its primary goal will be to explore the experimentally accessible parameter space for Weakly Interacting Massive Particles (WIMPs) in a wide mass-range, until neutrino interactions with the target become an irreducible background. The prompt scintillation light and the charge signals induced by particle interactions in the xenon will be observed by VUV sensitive, ultra-low background photosensors. Besides its excellent sensitivity to WIMPs above a mass of 5 GeV/ c {sup 2}, such a detector with its large mass, low-energy threshold and ultra-low background level will also be sensitive to other rare interactions. It will search for solar axions, galactic axion-like particles and the neutrinoless double-beta decay of {sup 136}Xe, as well as measure the low-energy solar neutrino flux with < 1% precision, observe coherent neutrino-nucleus interactions, and detect galactic supernovae. We present the concept of the DARWIN detector and discuss its physics reach, the main sources of backgrounds and the ongoing detector design and R and D efforts.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Correlated insulating states at fractional fillings of the WS 2 /WSe 2 moiré lattice

Moiré superlattices of van der Waals materials, such as twisted graphene and transitional metal dichalcogenides, have recently emerged as a fascinating platform to study strongly correlated states in two dimensions (2D), thanks to the strong electron interaction in the moiré minibands. In most systems, the correlated states appear when the moiré lattice is filled by integer number of electrons per moiré unit cell. Recently, correlated states at fractional fillings of 1/3 and 2/3 holes per moiré unit cell has been reported in the WS 2 /WSe 2 heterobilayer, hinting the long range nature of the electron interaction. In this work, employing a scanning microwave impedance microscopy technique that is sensitive to local electrical properties, we observe a series of correlated insulating states at fractional fillings of the moiré minibands on both electron- and hole-doped sides in angle-aligned WS 2 /WSe 2 hetero-bilayers, with certain states persisting at temperatures up to 120 K. Monte Carlo simulations reveal that these insulating states correspond to ordering of electrons in the moiré lattice with a periodicity much larger than the moiré unit cell, indicating a surprisingly strong and long-range interaction beyond the nearest neighbors. Our findings usher in unprecedented opportunities in the study of strongly correlated states in two dimensions.

36 MATERIALS SCIENCE↗
NASA NTRS1993

Interaction strength and model geometry effects on the structure of crossing-shock wave/turbulent boundary-layer interactions

The flowfield structure of a range of symmetric crossing-shock wave/turbulent boundary-layer interactions of varying strength is presented. The test geometry, consisting of a symmetric pair of opposing sharp fins at angle of attack, alpha, mounted to a flat plate, is studied experimentally for a range of alpha from 7 to 15 degrees at Mach numbers of 3 and 4. Results reveal that the basic flowfield shock structure remains similar in nature over the range of interaction strengths examined, with the only changes being in the scale and location of the various features present. The separated flow regions are classified as being either completely or partially separated, the completely separated case being the one in which the entire incoming boundary layer separates from the plate surface. For the current experiments, all but the weakest of the interactions exhibited complete boundary layer separation. Finally, the effects of model geometry are analyzed by comparing data for shock generators of varying lengths, with the results showing no evidence of upstream influence due to the shock generator trailing edges.

Garrison, T. J.↗
DOE OSTI2021

Assessing cathode property prediction via exchange-correlation functionals with and without long-range dispersion corrections

In this work, we benchmark calculated interlayer spacings, average topotactic voltages, thermodynamic stabilities, and band gaps in layered lithium transition-metal oxides (TMOs) and their de-lithiated counterparts, which are used in lithium-ion batteries as positive electrode materials, against available experimental data. Specifically, we examine the accuracy of properties calculated within density functional theory (DFT) using eight different treatments of electron exchange-correlation: the strongly constrained and appropriately normed (SCAN) and Perdew–Burke–Ernzerhof (PBE) density functionals, Hubbard-U-corrected SCAN and PBE (i.e., SCAN+U and PBE+U), and SCAN(+U) and PBE(+U) with added long-range dispersion (D) interactions (i.e., DFT(+U)+D). van der Waals interactions are included respectively via the revised Vydrov-Van Voorhis (rVV10) for SCAN(+U) and the DFT-D3 for PBE(+U). We find that SCAN-based functionals predict larger voltages due to an underestimation of stability of the MO2 systems, while also predicting smaller interlayer spacings compared to their PBE-based counterparts. Furthermore, adding dispersion corrections to PBE has a greater effect on voltage predictions and interlayer spacings than with SCAN, indicating that DFT-SCAN – despite being a ground-state theory – fortuitously captures some short and medium-range dispersion interactions better than PBE. While SCAN-based and PBE-based functionals yield qualitatively similar band gap predictions, there is no significant quantitative improvement of SCAN-based functionals over the corresponding PBE-based versions. Finally, we expect SCAN-based functionals to yield more accurate property predictions than the respective PBE-based functionals for most TMOs, given SCAN's stronger theoretical underpinning and better predictions of systematic trends in interlayer spacings, intercalation voltages, and band gaps obtained in this work.

25 ENERGY STORAGE↗
DOE OSTI2014

Multi-time Schrödinger equations cannot contain interaction potentials

Multi-time wave functions are wave functions that have a time variable for every particle, such as ϕ(t{sub 1},x{sub 1},...,t{sub N},x{sub N}). They arise as a relativistic analog of the wave functions of quantum mechanics but can be applied also in quantum field theory. The evolution of a wave function with N time variables is governed by N Schrödinger equations, one for each time variable. These Schrödinger equations can be inconsistent with each other, i.e., they can fail to possess a joint solution for every initial condition; in fact, the N Hamiltonians need to satisfy a certain commutator condition in order to be consistent. While this condition is automatically satisfied for non-interacting particles, it is a challenge to set up consistent multi-time equations with interaction. We prove for a wide class of multi-time Schrödinger equations that the presence of interaction potentials (given by multiplication operators) leads to inconsistency. We conclude that interaction has to be implemented instead by creation and annihilation of particles, which, in fact, can be done consistently [S. Petrat and R. Tumulka, “Multi-time wave functions for quantum field theory,” Ann. Physics (to be published)]. We also prove the following result: When a cut-off length δ > 0 is introduced (in the sense that the multi-time wave function is defined only on a certain set of spacelike configurations, thereby breaking Lorentz invariance), then the multi-time Schrödinger equations with interaction potentials of range δ are consistent; however, in the desired limit δ → 0 of removing the cut-off, the resulting multi-time equations are interaction-free, which supports the conclusion expressed in the title.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

The Bi{sub 2}O{sub 3}–Fe{sub 2}O{sub 3}–Sb{sub 2}O{sub 5} system phase diagram refinement, Bi{sub 3}FeSb{sub 2}O{sub 11} structure peculiarities and magnetic properties

The refinement of the Bi{sub 2}O{sub 3}–Fe{sub 2}O{sub 3}–Sb{sub 2}O{sub 5} system phase diagram has been performed and the existence of the two ternary compounds has been confirmed. The first one with a pyrochlore-type structure (sp. gr. Fd 3-barm) exists in the wide solid solution region, (Bi{sub 2−x}Fe{sub x})Fe{sub 1+y}Sb{sub 1−y}O{sub 7±δ}, where x=0.1–0.4 and y=−0.13–0.11. The second one, Bi{sub 3}FeSb{sub 2}O{sub 11}, corresponds to the cubic KSbO{sub 3}-type structure (sp. gr. Pn 3-bar) with unit cell parameter a=9.51521(2) Å. The Rietveld structure refinement showed that this compound is characterized by disordered structure. The Bi{sub 3}FeSb{sub 2}O{sub 11} factor group analysis has been carried out and a Raman spectrum has been investigated. According to magnetization measurements performed at the temperature range 2–300 K it may be concluded that the Bi{sub 3}FeSb{sub 2}O{sub 11} magnetic properties can be substantially described as a superposition of strong short-range antiferromagnetic exchange interactions realizing inside the [(FeSb{sub 2})O{sub 9}] 3D-framework via different pathways. - Graphical abstract: The refinement of the Bi{sub 2}O{sub 3}–Fe{sub 2}O{sub 3}–Sb{sub 2}O{sub 5} system phase diagram has been performed and the existence of the solid solution with a pyrochlore-type structure (sp. gr. Fd 3-barm) and Bi{sub 3}FeSb{sub 2}O{sub 11}, correspond of the cubic KSbO{sub 3}-type structure (sp. gr. Pn 3-bar has been confirmed. The structure refinement, Raman spectroscopy as well as magnetic measurements data of Bi{sub 3}FeSb{sub 2}O{sub 11} are presented. - Highlights: • The Bi{sub 2}O{sub 3}–Fe{sub 2}O{sub 3}–Sb{sub 2}O{sub 5} system phase diagram refinement has been performed. • The Bi{sub 3}FeSb{sub 2}O{sub 11} existence along with pyrochlore structure compound is shown. • It was determined that the Bi{sub 3}FeSb{sub 2}O{sub 11} is of disordered cubic KSbO{sub 3}-type structure. • Factor group analysis of Bi{sub 3}FeSb{sub 2}O{sub 11} vibrational spectrum has been performed. • Short-range antiferromagnetic interactions govern Bi{sub 3}FeSb{sub 2}O{sub 11} magnetic behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Wettability of partially suspended graphene

Dependence on the wettability of graphene on the nature of the underlying substrate remains only partially understood. We systematically investigate the role of liquid-substrate interactions on the wettability of graphene by varying the area fraction of suspended graphene from 0 to 95% by means of nanotextured substrates. We find that completely suspended graphene exhibits the highest water contact angle (85° ± 5°) compared to partially suspended or supported graphene, regardless of the hydrophobicity (hydrophilicity) of the substrate. Moreover, 80% of the long-range water-substrate interactions are screened by the graphene monolayer, the wettability of which is primarily determined by short-range graphene-liquid interactions. By its well-defined chemical and geometrical properties, supported graphene therefore provides a model system to elucidate the relative contribution of short and long range interactions to the macroscopic contact angle.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

The many-body electronic interactions of Fe(II)–porphyrin

Fe(II)–porphyrin complexes exhibit a diverse range of electronic interactions between the metal and macrocycle. Herein, the incremental full configuration interaction method is applied to the entire space of valence orbitals of a Fe(II)–porphyrin model using a modest basis set. A novel visualization framework is proposed to analyze individual many-body contributions to the correlation energy, providing detailed maps of this complex’s highly correlated electronic structure. Furthermore, this technique is used to parse the numerous interactions of two low-lying triplet states ( 3 A 2 g and 3 E g ) and to show that strong metal d–d and macrocycle π–π orbital interactions preferentially stabilize the 3 A 2 g state. d–π interactions, on the other hand, preferentially stabilize the 3 E g state and primarily appear when correlating six electrons at a time. Ultimately, the Fe(II)–porphyrin model’s full set of 88 valence electrons are correlated in 275 orbitals, showing the interactions up to the 4-body level, which covers the great majority of correlations in this system.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

High spin structure of $\mathrm{^{39}Ar}$ and the FSU cross-shell interaction

High-spin states in $\mathrm{^{39}Ar}$ were populated using the $\mathrm{^{27}Al(^{14}C,} pn)$ reaction at 25.6 MeV. The de-exciting $γ$ rays were measured with the FSU $γ$ detector array along with evaporation protons in a Si $E-ΔE$ telescope. The known high-spin level scheme was extended up to over 11 MeV with a dozen new levels above the neutron decay threshold. The decay pattern appears somewhat atypical for heavy-ion fusion-evaporation reactions. The structure of $\mathrm{^{39}Ar}$ is discussed in terms of the new FSU cross-shell $spsdpf$ interaction fitted to a wide range of nuclei. This interaction has proved quite successful in accounting for the level scheme of $\mathrm{^{39}Ar}$, including the previously suggested fully aligned $πf_{7/2} Ⓧ νf_{7/2}17/2^+$ state and previously discovered analogs of the lowest states in $\mathrm{^{39}Cl}$.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Asymptotic optimality of twist-untwist protocols for Heisenberg scaling in atom-based sensing

Twist-untwist protocols for quantum metrology consist of a serial application of (1) unitary nonlinear dynamics (e.g., spin squeezing or Kerr nonlinearity), (2) parameterized dynamics U ( φ ) (e.g., a collective rotation or phase space displacement), and (3) time reversed application of step 1. Such protocols are known to produce states that allow Heisenberg scaling for experimentally accessible estimators of φ even when the nonlinearities are applied for times much shorter than required to produce Schrödinger cat states. In this work, we prove that, asymptotically in the number of particles, twist-untwist protocols provide the lowest estimation error among quantum metrology protocols that utilize two calls to a weakly nonlinear evolution and a readout involving only first and second moments of a total spin operator n → · J → . We consider the following physical settings: all-to-all interactions generated by one-axis twisting J z 2 (e.g., interacting Bose gases), constant finite range spin-spin interactions of distinguishable or bosonic atoms (e.g., trapped ions or Rydberg atoms, or lattice bosons). In these settings, we further show that the optimal twist-untwist protocols asymptotically achieve 85% and 92% of the respective quantum Cramér-Rao bounds. We show that the error of a twist-untwist protocol can be decreased by a factor of L without an increase in the noise of the spin measurement if the twist-untwist protocol can be noiselessly iterated as an L layer quantum alternating operator ansatz.

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRS1972

Satellite aerodynamics as a function of atmospheric properties.

Demonstration that satellite aerodynamic properties are a function of numerous factors associated with atmospheric properties. Among these factors, the gas composition has influence on the gas surface interaction which in turn has considerable influence on the satellite drag and lift properties. The drag and lift properties, which are also influenced by the orientation of the satellite with respect to the flow, are influenced by upper atmospheric winds which cause changes in the angle of attack of the satellite. Another strong influence on the aerodynamic properties is due to the speed ratio effect which is found to cause a systematic increase in drag coefficient with respect to altitude. The study of these factors is facilitated by the introduction of a generalized gas surface interaction model which is capable of representing a wide range of possible interactions.

Karr, G. R.↗
DOE OSTI2014

Mechanism of multi-defect induced ferromagnetism in undoped rutile TiO{sub 2}

Based on first-principles calculations, the coexistence of Ti vacancies (V{sub Ti}) and O vacancies (V{sub O}) is first considered to study the origin of the ferromagnetic ordering in undoped rutile TiO{sub 2}. The calculations show that V{sub O} can induce local magnetic moments in TiO{sub 2}, however, the ferromagnetic (FM) exchange interaction of two V{sub O} is not strong enough to induce room-temperature (RT) ferromagnetism on their own in undoped TiO{sub 2}. The FM coupling between two V{sub Ti} is about four times stronger than that between two V{sub O}. More importantly, the FM coupling between two V{sub Ti} is further enhanced after V{sub O} is introduced. Our results indicate that the electrons induced by V{sub O} mediate the long-range FM exchange interaction between two distant V{sub Ti}. This maybe the ferromagnetism mechanism in undoped TiO{sub 2}: V{sub Ti} produce local moments while the electrons induced by V{sub O} mediated the long-range FM exchange interaction. The results are in excellent agreement with the experimental evidences that V{sub O} alone cannot induce RT ferromagnetism while V{sub O} can promote the ferromagnetic ordering in undoped TiO{sub 2}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Order of wetting transitions in electrolyte solutions

For wetting films in dilute electrolyte solutions close to charged walls we present analytic expressions for their effective interface potentials. The analysis of these expressions renders the conditions under which corresponding wetting transitions can be first- or second-order. Within mean field theory we consider two models, one with short- and one with long-ranged solvent-solvent and solvent-wall interactions. The analytic results reveal in a transparent way that wetting transitions in electrolyte solutions, which occur far away from their critical point (i.e., the bulk correlation length is less than half of the Debye length) are always first-order if the solvent-solvent and solvent-wall interactions are short-ranged. In contrast, wetting transitions close to the bulk critical point of the solvent (i.e., the bulk correlation length is larger than the Debye length) exhibit the same wetting behavior as the pure, i.e., salt-free, solvent. If the salt-free solvent is governed by long-ranged solvent-solvent as well as long-ranged solvent-wall interactions and exhibits critical wetting, adding salt can cause the occurrence of an ion-induced first-order thin-thick transition which precedes the subsequent continuous wetting as for the salt-free solvent.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1994

Heat-transfer measurements and computations of swept-shock-wave boundary-layer interactions

An experimental and computational research program providing new knowledge of the heat transfer in swept-shock-wave/boundary-layer interactions is described. An equilibrium turbulent boundary layer on a flat plate is subjected to impingement by a swept planar shock wave generated by a sharp fin. Five different interactions with fin angles ranging from 10 to 20 deg at freestream Mach numbers of 3 and 4 produce a variety of interaction strengths ranging from weak to very strong. A foil heater generates a uniform heat flux over the flat plate surface, and miniature thin-film-resistance sensors are used to measure the local surface temperature. The heat convection equation is then solved for the heat transfer distribution within an interaction, yielding an uncertainty of about +/- 10%. These data are compared with numerical Navier-Stokes solutions that employ a k-epsilon turbulence model. A simple peak heat transfer correlation for fin interactions is suggested.

Lee, Y.↗