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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Low-temperature thermostatics of face-centered-cubic metallic hydrogen

The thermostatic properties of a high-symmetry phase of metallic hydrogen with atomic sphere radius between 0.1 and 1.5 bohr are studied, with special emphasis accorded to electronic screening and quantum proton motion. The electron-proton and proton-proton interactions receive a perturbation treatment based on the Singwi dielectric function, while the proton motion is handled by self-consistent harmonic approximation. Quantum behavior is found to be less pronounced than expected, and nuclear magnetism is absent. The phonon spectrum is, however, affected by screening and large proton motion. The zero-point vibrational energy and the superconducting critical temperature are below previous estimates. The crystalline-defect formation energies are a few times the Debye energy, which implies that defects contribute significantly to melting at the lower particle densities.

Caron, L. G.↗
NASA NTRS1985

Adsorption and recombination of hydrogen atoms on a model graphite surface

The adsorption and recombination of atomic hydrogen on a model graphite grain have been examined in a series of calculations in which a modified, iterative, extended Hueckel program was used. The hydrogen atom is found to be chemisorbed at a site with a zero-point binding energy of 0.7 eV and at an equilibrium distance of 2.25 A above the site. Despite a barrier of about 0.4 eV between adjacent sites, calculations suggest that at temperatures as low as 10 K, an H atom will tunnel through to adjacent sites in less than one nanosecond. However, a potential barrier to the recombination of two hydrogen atoms has been found which displays high sensitivity to the mutual arrangement of the two hydrogen atoms with respect to the graphite surface. Results show that at very low temperatures, recombinations can occur only by tunneling. Consistent with experiment, the region in which H2 begins to form exhibits a repulsive potential with respect to possible chemisorption of the incipient H2 entity.

Aronowitz, S.↗
DOE OSTI2022

Two-atom-thin topological crystalline insulators lacking out of plane inversion symmetry

A two-dimensional topological crystalline insulator (TCI) with a single unit cell (u.c.) thickness is demonstrated here. To that end, one first shows that tetragonal (C 4 in-plane) symmetry is not a necessary condition for the creation of zero-energy metallic surface states on TCI slabs of finite-thicknesses, because zero-energy states persist even as all the in-plane rotational symmetries—furnishing topological protection—are completely removed. In other words, zero-energy levels on the model are not due to (nor are they protected by) topology. Furthermore, effective two-fold energy degeneracies taking place at few discrete k-points away from zero energy in the bulk Hamiltonian—that are topologically protected—persist at the u.c. thickness limit. Here, the chiral nature of the bulk TCI Hamiltonian permits creating a $2\times 2$ square Hamiltonian, whose topological properties remarkably hold invariant at both the bulk and at the single u.c. thickness limits. The identical topological characterization for bulk and u.c.-thick phases is further guaranteed by a calculation involving Pfaffians. This way, a two-atom-thick TCI is deployed hereby, in a demonstration of a topological phase that holds both in the bulk, and in two dimensions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

A Many-Body Perspective of Nuclear Quantum Effects in Aqueous Clusters

Nuclear quantum effects play an important role in the structure and thermodynamics of aqueous systems. Here, by performing a many-body expansion with nuclear-electronic orbital (NEO) theory, we show that proton quantization can give rise to significant energetic contributions for many-body interactions spanning several molecules in single-point energy calculations of water clusters. Although zero-point motion produces a large increase in energy at the one-body level, nuclear quantum effects serve to stabilize higher-order molecular interactions. These results are significant because they demonstrate that nuclear quantum effects play a nontrivial role in many-body interactions of aqueous systems. Our approach also provides a pathway for incorporating nuclear quantum effects into water potential energy surfaces. The NEO approach is advantageous for many-body expansion analyses because it includes nuclear quantum effects directly in the energies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

The DESI DR1 Peculiar Velocity Survey: Global Zero-point and H 0 Constraints

The Dark Energy Spectroscopic Instrument (DESI) in its first Data Release (DR1) already provides more than 100,000 galaxies with relative distance measurements. The primary purpose of this paper is to perform the calibration of the zero-point for the DESI Fundamental Plane and Tully–Fisher relations, which allows us to measure the Hubble constant, H 0 . This sample has a lower statistical uncertainty than any previously used to measure H 0 , and we investigate the systematic uncertainties in absolute calibration that could limit the accuracy of that measurement. We improve upon the DESI Early Data Release Fundamental Plane H 0 measurement by (a) using a group catalog to increase the number of calibrator galaxies and (b) investigating alternative calibrators in the nearby Universe. Our baseline measurement calibrates to the SH0ES/Pantheon+ type Ia supernovae, and finds H 0 = 73.7 ± 0.06 (stat.) ± 1.1 (syst.) km s −1 Mpc −1 . Calibrating to surface brightness fluctuation distances yields a similar H 0 . We explore measurements using other calibrators, but these are currently less precise since the overlap with DESI peculiar velocity tracers is much smaller. In future data releases with an even larger peculiar velocity sample, we plan to calibrate directly to Cepheids and the tip of the red giant branch, which will enable the uncertainty to decrease towards a percent-level measurement of H 0 . This will provide an alternative to supernovae as the Hubble flow sample for H 0 measurements.

Carr, Anthony [Korea Astronomy and Space Science I↗
DOE OSTI2021

Topological Mott transition in a two band model of spinless fermions with on-site Coulomb repulsion

Highlights: • The effect of the on-site Coulomb repulsion and the spin–orbit Rashba coupling lead to the 2D topological semimetal. • The ground state phase diagram is calculated. • The topological semimetal phase is characterized by the zero energy Majorana states. In the framework of mean field approach, we study topological Mott transition in a two band model of spinless fermions on a square lattice at half filling. We consider the combined effect of the on-site Coulomb repulsion and the spin–orbit Rashba coupling. The ground state phase diagram is calculated as a function of the strength of the spin–orbit Rashba coupling and the Coulomb repulsion. The spin–orbit Rashba coupling leads to a distinct phase of matter, the topological semimetal. We study a new type of phase transition between the non-topological insulator and topological semimetal states. Topological phase state is characterized by the zero energy Majorana states, which there are in defined region of the wave vectors and are localized at the boundaries of the sample. The region of existence of the zero energy Majorana states tends to zero at the point of the Mott phase transition. The zero energy Majorana states are dispersionless (they can be considered as flat bands), the Chern number and Hall conductance are equal to zero (note in two dimensional model).

36 MATERIALS SCIENCE↗
NASA NTRS1989

Reversal electron attachment ionizer for detection of trace species

An in-line reversal electron, high-current ionizer capable of focusing a beam of electrons to a reversal region and executing a reversal of the electrons, such that the electrons possess zero kinetic energy at the point of reversal, may be used to produce both negative and positive ions. A sample gas is introduced at the point of electron reversal for low energy electron-(sample gas) molecule attachment with high efficiency. The attachment process produces negative ions from the sample gas, which includes species present in trace (minute) amounts. These ions are extracted efficiently and directed to a mass analyzer where they may be detected and identified. The generation and detection of positive ions is accomplished in a similar fashion with minimal adjustment to potentials applied to the apparatus.

Bernius, Mark T.↗
NASA NTRS1990

Reversal electron attachment ionizer for detection of trace species

An in-line reversal electron, high-current ionizer capable of focusing a beam of electrons to a reversal region and executing a reversal of said electrons, such that the electrons possess zero kinetic energy at the point of reversal, may be used to produce both negative and positive ions. A sample gas is introduced at the point of electron reversal for low energy electron-(sample gas) molecule attachment with high efficiency. The attachment process produces negative ions from the sample gas, which includes species present in trace (minute) amounts. These ions are extracted efficiently and directed to a mass analyzer where they may be detected and identified. The generation and detection of positive ions is accomplished in a similar fashion with minimal adjustment to potentials applied to the apparatus.

Bernius, Mark T.↗
NASA NTRS1989

Pulsed, high-current, in-line reversal electron attachment detector

A new, pulsed, high-current, in-line reversal electron attachment ionizer/detector is described. The ionizer is capable of delivering a beam of electrons into an electrostatic mirror field to form a planar wall of electrons having zero kinetic energy. Electron attachment to a molecular target at the reversal point produces either parent or fragment negative ions through a zero-energy (s-wave) state. The atomic or molecular ion is pulsed out of the attachment region approximately 2 microsec after the electrons are pulsed off, and focused onto the entrance plane of a quadrupole mass analyzer. The sensitivity of the apparatus is preliminarily assessed, and its higher-energy behavior with regard to molecular attachment and ionization is described.

Bernius, Mark T.↗
DOE OSTI2022

Digital pulse analysis for fast neutron recoil spectroscopy with a 4 He scintillation detector

Helium-4-based fast neutron scintillation detectors are an attractive alternative to pulse-shape discrimination-capable organic scintillators for fast neutron detection and spectroscopy, as the response of the detectors to gamma rays is intrinsically limited to low energy deposition. Consequently, the neutron recoil distribution can be measured with these detectors without the need for pulse shape analysis. In this work, the response of an Arktis S670 4 He scintillation detector to D-D, D-T, and 252 Cf neutrons was measured. The detector has a unique construction and readout mechanism, with multiple output channels observing the same scintillation event, and an analysis method was developed to aggregate the outputs from all channels into a single list. The D-D and D-T neutron responses were used to perform a two-point energy calibration, which yielded a near-zero intercept, suggesting that the 4 He scintillation medium behaves linearly to a higher energy than previously reported, and that a two-point calibration is sufficient for nuclear recoil energies below 9 MeV. As a result, the detector was measured to have 16.7-ns FWHM time resolution when using the developed custom analysis, a reduction of 4.9 ns when compared to the conventional pulse analysis.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1992

Negative-ion formation in the explosives RDX, PETN, and TNT using the Reversal Electron Attachment Detection (READ) technique

In the search for high sensitivity and direct atmospheric sampling of trace species, techniques have been developed such as atmospheric-sampling, glow-discharge ionization (ASGDI), corona discharge, atmospheric pressure ionization (API), electron-capture detection (ECD), and negative-ion chemical ionization (NICI) that are capable of detecting parts-per-billion to parts-per-trillion concentrations of trace species. These techniques are based on positive- or negative-ion formation via charge-transfer to the target, or electron capture under multiple-collision conditions in a Maxwellian distribution of electron energies at the source temperature. One drawback of the high-pressure, corona- or glow-discharge devices is that they are susceptible to interferences either through indistinguishable product masses, or through undesired ion-molecule reactions. The ASGDI technique is relatively immune from such interferences, since at target concentrations of less than 1 ppm the majority of negative ions arises via electron capture rather than through ion-molecule chemistry. A drawback of the conventional ECD, and possibly of the ASGDI, is that they exhibit vanishingly small densities of electrons with energies in the range 0-10 millielectron volts (meV), as can be seen from a typical Maxwellian electron energy distribution function at T = 300 K. Slowing the electrons to these subthermal (less than 10 meV) energies is crucial, since the cross section for attachment of several large classes of molecules is known to increase to values larger than 10(exp -12) sq cm at near-zero electron energies. In the limit of zero energy these cross sections are predicted to diverge as epsilon(exp -1/2), where epsilon is the electron energy. In order to provide a better 'match' between the electron energy distribution function and attachment cross section, a new concept of attachment in an electrostatic mirror was developed. In this scheme, electrons are brought to a momentary halt by reversing their direction with electrostatic fields. At this turning point the electrons have zero or near-zero energy. A beam of target molecules is introduced, and the resultant negative ions extracted. This basic idea has been recently improved to allow for better reversal geometry, higher electron currents, lower backgrounds, and increased negative-ion extraction efficiency. We present herein application of the so-called reversal electron attachment detector (READ) to the study of negative-ion formation in the explosives molecules RDX, PETN, and TNT under single-collision conditions.

Chutijian, Ara↗
DOE OSTI2026

Chirality reversal at finite magnetic impurity strength and local signatures of a topological phase transition

Here, we study the honeycomb lattice with a single magnetic impurity modeled by adding imaginary next-nearest-neighbor hopping 𝑖⁢ℎ on a single hexagon. This Haldane defect gives a topological mass term to the gapless Dirac cones and generates chirality. For a small density of defects, Neehus et al. [Phys. Rev. Lett. 135, 126604 (2025)] found that the system's chirality reverses at a critical ℎ 𝑐 ≈ 0.95 associated with an unexpected tricritical point of Dirac fermions at zero defect density. We investigate this zero-density limit by analyzing a single defect and computing two experimentally relevant measures of chirality: (1) orbital magnetization via local Chern marker, a bulk probe of all occupied states; and (2) electronic currents of low-energy states. Both probes show a chirality reversal at a critical ℎ 𝑐 ≈ 0.9–1.0. Motivated by this consistency, we propose a defect-scale toy model whose low-energy states reverse their chirality at ℎ$^{'}_{c}$ ≈ 0.87. Remarkably, the same pair of zero-energy bound states also generates the critical point ℎ 𝑐 in the full impurity projected T-matrix. Our results show how the chirality reversal produced by an impurity can be observed either in local probes or in the global topology, and suggest a possible role of the microscopic defect structure at the critical point.

Chern insulators↗
NASA NTRS2017

Thermal Expansion from Stochastic Nonlinear Acoustic Fields

The methods of stochastic mechanics are applied to nonlinear acoustic fields generated by random acoustic radiation sources associated with oscillating lattice sites in nonlinear lattices. The assumption of stochastically independent zero-point and temperature-dependent acoustic fields leads to expressions of the thermodynamic internal and Helmholtz free energies per unit mass in terms of modal energies per unit mass that account for the nonlinearity of the propagation modes. The thermodynamic state functions canonically transform to the familiar results of a system of quantized, simple harmonic oscillators in the linear field limit. The thermal expansion coefficient, derived from the Helmholtz free energy per unit mass, is obtained as a sum of the zero-point modal nonlinearity parameters, weighted by temperature-dependent, modal heat capacities. The relationship is fully anharmonic, in contrast to commonly used quasi-harmonic models, and predicts with excellent agreement the experimentally observed null thermal expansion of vitreous silica at the ‘cross-over’ temperature corresponding to the balance between long wavelength modes that contribute negative nonlinearity parameters to the modal sum and short wavelength modes that contribute positive nonlinearity parameters.

Cantrell, John H., Jr.↗
DOE OSTI2025

Anharmonic phonons, thermal expansion, and nuclear quantum effects in Zn

The anharmonic behavior of phonons and thermal expansion of hexagonal zinc were studied from 15 to 690 K by inelastic neutron scattering (INS) and ab initio simulations. Phonon spectra were measured for Q-points covering the full Brillouin zone, giving the phonon density of states (DOS) and dispersions along high-symmetry directions. The dispersions were sharp at 15 K, but diffuse intensity was observed at energies above them. The dispersions broadened with temperature T and the diffuse intensity became stronger. This diffuse intensity appeared in all INS measurements and simulations, except for classical molecular dynamics at 15 K. The temperature-dependent effective potential (TDEP) method, which included the nuclear quantum effect from zero-point vibrational dynamics, was used to calculate the free energy and thermal expansion. For T < 100 K nuclear quantum effects were important for obtaining the correct negative thermal expansion, and path integral molecular dynamics (PIMD) was particularly effective for obtaining the negative thermal expansion in the basal plane. A Heisenberg-Langevin model for interacting phonons coupled to a thermal bath was able to reproduce the shape and intensity of the diffuse spectral features.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

GridSTIX

SF-25-112 Grid-STIX is a comprehensive extension of the STIX (Structured Threat Information Expression) 2.1 ontology specifically designed for electrical grid cybersecurity applications. This ontology provides a standardized, machine-readable framework for modeling grid assets, operational technology devices, threats, vulnerabilities, supply chain risks, and security relationships in electrical power systems. ## Key Features - **Comprehensive Grid Coverage**: Physical assets, OT devices, grid components, sensors, and energy storage systems - **Zero Trust Architecture**: Policy decision points, enforcement points, trust brokers, and continuous monitoring - **AMI Infrastructure**: Advanced metering networks, head-end systems, mesh gateways, and MDM systems - **Advanced Security Modeling**: Attack patterns, vulnerabilities, mitigations, and supply chain risks - **Critical Grid Relationships**: Power flow, protection, control, and synchronization relationships - **Supply Chain Security**: Supplier modeling, country of origin tracking, and risk assessment - **Protocol Support**: DNP3, Modbus, IEC 61850, IEC 60870-5-104, OPC-UA, and IEEE standards - **Python Code Generation**: Automated STIX-compliant Python class generation from ontologies - **Interactive Visualization**: Enhanced HTML network graphs with grid-specific categorization - **STIX 2.1 Compliance**: Full compatibility with STIX threat intelligence ecosystem

Blakely, Benjamin [Argonne National Laboratory (AN↗
DOE OSTI2020

Band gap renormalization, carrier mobilities, and the electron-phonon self-energy in crystalline naphthalene

Organic molecular crystals are expected to feature appreciable electron-phonon interactions that influence their electronic properties at zero and finite temperature. Here, we report first-principles calculations and an analysis of the electron-phonon self-energy in naphthalene crystals. We compute the zero-point renormalization and temperature dependence of the fundamental band gap, and the resulting scattering lifetimes of electronic states near the valence- and conduction-band edges employing density functional theory. Further, our calculated phonon renormalization of the GW-corrected quasiparticle band structure predicts a fundamental band gap of 5 eV for naphthalene at room temperature, in good agreement with experiments. From our calculated phonon-induced electron lifetimes, we obtain the temperature-dependent mobilities of electrons and holes in good agreement with experimental measurements at room temperature. Finally, we show that an approximate energy self-consistent computational scheme for the electron-phonon self-energy leads to the prediction of strong satellite bands in the electronic band structure. We find that a single calculation of the self-energy can reproduce the self-consistent results of the band gap renormalization and electrical mobilities for naphthalene, provided that the on-the-mass-shell approximation is used, i.e., if the self-energy is evaluated at the bare eigenvalues.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Dependence of Cosmological Constraints on Gray Photometric Zero-point Uncertainties of Supernova Surveys

Abstract Type Ia supernova (SN) measurements of the Hubble constant, H 0 ; cosmic mass density, Ω M ; and dark energy equation-of-state parameter, w , rely on heterogeneous SN surveys across three decades of observation. These distinct surveys may have undiagnosed, relative photometric zero-point errors. We determine the sensitivities of the SH0ES+Pantheon+ cosmological constraints to unknown gray systematics in the photometric zero-point calibration between the 19 surveys that comprise the Pantheon+ SN compendium. Varying the surveys’ gray zero-points simultaneously with cosmological parameters, we determine that the SH0ES+Pantheon+ measurement of H 0 is robust against gray intersurvey photometric miscalibration. Specifically, uncalibrated intersurvey systematics could represent a source of uncertainty no larger than 0.39 km s −1 Mpc −1 for H 0 . This modest increase in H 0 uncertainty could not account for the 7 km s −1 Mpc −1 “Hubble tension” between the SH0ES measurement of H 0 and the Planck ΛCDM-based inference of H 0 . However, the SH0ES+Pantheon+ best-fit values of Ω M and w are not robust against gray zero-point error, slipping by up to 0.16 and −0.63. Because measurements of Ω M and w depend on intrasurvey cross-band calibration, the hypothetical gray miscalibration underestimates the sensitivity of these measurements to zero-point miscalibration. Because the Pantheon+ compendium contains many surveys that share low- z Hubble flow (HF) and Cepheid-paired SNe, intersurvey photometric calibration errors do not significantly impede the joint use of SH0ES and Pantheon+ to measure H 0 to 1% accuracy. However, H 0 constraints that rely on one HF survey but numerous galactic distance calibration surveys are susceptible to intersurvey photometric miscalibration.

79 ASTRONOMY AND ASTROPHYSICS↗