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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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9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Revealing the structure of light pseudoscalar mesons at the electron–ion collider

The questions of how the bulk of the Universe's visible mass emerges and how it is manifest in the existence and properties of hadrons are profound, and probe the heart of strongly interacting matter. Paradoxically, the lightest pseudoscalar mesons appear to be key to a further understanding of the emergent mass and structure mechanisms. These mesons, namely, the pion and kaon, are the Nambu-Goldstone boson modes of quantum chromodynamics (QCD). Unravelling their partonic structure and the interplay between emergent and Higgs-boson mass mechanisms is a common goal of three interdependent approaches - continuum QCD phenomenology, lattice-regularised QCD, and the global analysis of parton distributions - linked to experimental measurements of hadron structure. Experimentally, the anticipated electron-ion collider will enable a revolution in our ability to study pion and kaon structures, accessed by scattering from the 'meson cloud' of the proton through the Sullivan process. With the goal of enabling a suite of measurements that can address these questions, we examine key reactions that identify the critical detector-system requirements needed to map tagged pion and kaon cross-sections over a wide range of kinematics. The excellent prospects for extracting pion structural, functional, and form-factor data are outlined, and similar prospects for kaon structures are discussed in the context of a worldwide programme. Finally, the successful completion of the programme outlined herein will deliver deep, far-reaching insights into the emergence of pions and kaons, their properties, and their role as QCD's Goldstone boson modes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Theoretical tools for neutrino scattering: interplay between lattice QCD, EFTs, nuclear physics, phenomenology, and neutrino event generators

Maximizing the discovery potential of increasingly precise neutrino experiments will require an improved theoretical understanding of neutrino-nucleus cross sections over a wide range of energies. Low-energy interactions are needed to reconstruct the energies of astrophysical neutrinos from supernovae bursts and search for new physics using increasingly precise measurement of coherent elastic neutrino scattering. Higher-energy interactions involve a variety of reaction mechanisms including quasi-elastic scattering, resonance production, and deep inelastic scattering that must all be included to reliably predict cross sections for energies relevant to DUNE and other accelerator neutrino experiments. Refined nuclear interaction models in these energy regimes will also be valuable for other applications, such as measurements of reactor, solar, and atmospheric neutrinos. This manuscript discusses the theoretical status, challenges, required resources, and path forward for achieving precise predictions of neutrino-nucleus scattering and emphasizes the need for a coordinated theoretical effort involved lattice QCD, nuclear effective theories, phenomenological models of the transition region, and event generators.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Plasmon spectroscopy for the determination of Ti 3 C 2 T x MXene few layer stacks architecture

Like many 2D materials, numerous properties of MXene multilayers, and especially the most popular one Ti 3 C 2 T x , have been shown to significantly depend on their architecture, i.e. the number of layers and interlayer distance. These structural parameters are thus key elements to be characterized for the analysis of MXene properties. Focusing on valence electron energy-loss spectroscopy (VEELS) as performed in a transmission electron microscope (TEM), and using density functional theory (DFT) simulations, we here analyze the layer dependent large changes in the VEEL spectra of Ti 3 C 2 T x multilayers as a probe of their total thickness, and emphasize the bulk plasmon energy sensitivity to interlayer distance. Together these findings allow to directly quantify the absolute number of layers in a Ti 3 C 2 T x stack up to ~10 nm thickness and give access to interlayer distance modifications with sub-angström sensitivity, evidencing VEELS as a powerful method for the characterization of MXene multilayers on the nanometer scale. We expect these results to be relevant for the study of structure/properties correlations in this class of materials, especially with the development of in situ or environmental TEM experiments.

Materials Science↗
DOE OSTI2022

Probing the Galactic halo with RR Lyrae stars – II. The substructures of the Milky Way

ABSTRACT We identify substructures of the Galactic halo using 3003 type ab RR Lyrae stars with six-dimensional position–velocity information from the Sloan Digital Sky Survey, the Large Sky Area Multi-Object Fiber Spectroscopic Telescope and the Gaia Early Data Release 3. Based on this information, we define the separation of any two of the stars in the integrals of motion space and we identify substructures by utilizing the friends-of-friends algorithm. We identify members belonging to several known substructures: the Sagittarius stream, the Gaia-Enceladus-Sausage (GES), the Sequoia and the Helmi streams. In addition to these known substructures, there are three other substructures possibly associated with globular clusters NGC 5272, 6656 and 5024, respectively. Finally, we also find three remaining unknown substructures, one of which has large angular momentum and a mean metallicity −2.13 dex, which may be a new substructure. As for the GES, we find that it accounts for a large part of substructures in the inner halo and the apocentre distance is in the range 10–34 kpc, which suggests that the GES is mainly distributed in the inner halo. The near one-third proportion of the GES and the peak value of 20 kpc of the apocentre distance suggest that the GES could account for the break in the density profile of the Galactic halo at the Galactocentric distance ~20–25 kpc. The similarity when comparing the kinematic properties of the GES with the Hercules–Aquila Cloud and Virgo Overdensity suggests that the three substructures may have similar origins.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Materials Data on HW by Materials Project

HW1 is Molybdenum Carbide MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. W is bonded in a 6-coordinate geometry to six equivalent H atoms. All W–H bond lengths are 2.08 Å. H is bonded to six equivalent W atoms to form a mixture of face, edge, and corner-sharing HW6 octahedra. The corner-sharing octahedral tilt angles are 48°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H5W by Materials Project

WH5 crystallizes in the orthorhombic Pma2 space group. The structure is two-dimensional and consists of one WH5 sheet oriented in the (0, 1, 0) direction. W3+ is bonded in a 12-coordinate geometry to ten H+0.60- atoms. There are a spread of W–H bond distances ranging from 1.76–2.05 Å. There are three inequivalent H+0.60- sites. In the first H+0.60- site, H+0.60- is bonded in a water-like geometry to two equivalent W3+ atoms. In the second H+0.60- site, H+0.60- is bonded in a water-like geometry to two equivalent W3+ atoms. In the third H+0.60- site, H+0.60- is bonded in a 1-coordinate geometry to two equivalent W3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H3W by Materials Project

WH3 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. W3+ is bonded in a 8-coordinate geometry to eight H1- atoms. There are a spread of W–H bond distances ranging from 1.81–2.11 Å. There are three inequivalent H1- sites. In the first H1- site, H1- is bonded in a distorted trigonal planar geometry to three equivalent W3+ atoms. In the second H1- site, H1- is bonded in a bent 120 degrees geometry to two equivalent W3+ atoms. In the third H1- site, H1- is bonded in a trigonal non-coplanar geometry to three equivalent W3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H3W by Materials Project

WH3 crystallizes in the monoclinic P2_1/m space group. The structure is two-dimensional and consists of one WH3 sheet oriented in the (0, 0, 1) direction. W3+ is bonded in a 9-coordinate geometry to nine H1- atoms. There are a spread of W–H bond distances ranging from 1.81–2.36 Å. There are three inequivalent H1- sites. In the first H1- site, H1- is bonded in a water-like geometry to two equivalent W3+ atoms. In the second H1- site, H1- is bonded in a water-like geometry to two equivalent W3+ atoms. In the third H1- site, H1- is bonded in a 5-coordinate geometry to five equivalent W3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H4W by Materials Project

WH4 crystallizes in the tetragonal P4/nmm space group. The structure is two-dimensional and consists of one WH4 sheet oriented in the (0, 0, 1) direction. W2+ is bonded in a 10-coordinate geometry to ten H+0.50- atoms. There are a spread of W–H bond distances ranging from 1.73–2.18 Å. There are three inequivalent H+0.50- sites. In the first H+0.50- site, H+0.50- is bonded to five equivalent W2+ atoms to form a mixture of distorted corner and edge-sharing HW5 square pyramids. In the second H+0.50- site, H+0.50- is bonded in a single-bond geometry to one W2+ atom. In the third H+0.50- site, H+0.50- is bonded in a water-like geometry to two equivalent W2+ atoms.

36 MATERIALS SCIENCE↗