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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 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Stability of Panels of a Thermoelastic Shell Heated at the Edge by a Mobile Point Source

The thermostability of thin-walled structures is considered by means of a thermoelasticity problem in a three-dimensional quasi-static formulation. Finite-element models of panels in the form of a circular cylinder and a plate reinforced by ribs are constructed. Numerical solutions are obtained for the stability loss of thermoelastic thin-walled reinforced structures with intense edge heating by a mobile heat source.

42 ENGINEERING↗
DOE OSTI2018

Nanodiamond‐Palladium Core–Shell Organohybrid Synthesis: A Mild Vapor‐Phase Procedure Enabling Nanolayering Metal onto Functionalized sp 3 ‐Carbon

Abstract A novel approach for the bottom‐up construction of hybrid organic–inorganic nanocomposites with an intimate arrangement between sp 3 ‐carbon 3D molecular‐size nanodiamonds (diamondoids) and a coated palladium surface as nanolayer is reported. The construction process is conducted stepwisely from the gas phase, using first controlled vapor‐phase self‐assembly of tailor‐made functionalized diamantane derivatives, followed by low‐temperature (45 °C) chemical vapor deposition of an organometallic complex in a reducing H 2 atmosphere over the self‐assembled diamondoid scaffold. The use of self‐assemblies of primary diamantane phosphine and phosphine oxide, which are produced with high structural uniformity and reproducibility, yields new hybrid diamondoid‐palladium materials incorporating PdOPHdiamantane bonding motifs. Additional investigations provide evidence for a very challenging issue in the intimate construction of sp 3 ‐C/metal scaffolds. Scanning electron microscopy and transmission electron microscopy microscopies combined with X‐ray photoelectron spectroscopy surface analysis and EDX bulk analysis confirm the formation of diamondoid‐palladium organohybrids with unique surface layering. The vapor phase‐controlled mild synthetic process allows excellent control over nanocomposite formation and morphology from molecular‐level modifications. As such, this bottom‐up composite building process bridges scales from the molecular (functionalized diamondoids) over nanoscopic (self‐assemblies) to microscopic regime (hybrids), in the challenging association of transition metals with an electronically saturated sp 3 ‐carbon organic host material.

Gunawan, Maria A.↗
DOE OSTI2022

Activating Single‐Atom Ni Site via First‐Shell Si Modulation Boosts Oxygen Reduction Reaction

Abstract Atomically dispersed nitrogen‐coordinated 3d transition‐metal site on carbon support (M‐NC) are promising alternatives to Pt group metal‐based catalysts toward oxygen reduction reaction (ORR). However, despite the excellent activities of most of M‐NC catalysts, such as Fe‐NC, Co‐NC et al., their durability is far from satisfactory due to Fenton reaction. Herein, this work reports a novel Si‐doped Ni‐NC catalyst (Ni‐SiNC) that possesses high activity and excellent stability. X‐ray absorption fine structure and aberration‐corrected transmission electron microscopy uncover that the single‐atom Ni site is coordinated with one Si atom and three N atoms, constructing Ni‐Si 1 N 3 moiety. The Ni‐SiNC catalyst exhibits a half‐wave potential (E 1/2 ) of 0.866 V versus RHE, with a distinguished long‐term durability in alkaline media of only 10 mV negative shift in E 1/2 after 35 000 cycles, which is also validated in Zn‐air battery. Density functional theory calculations reveal that the Ni‐Si 1 N 3 moiety facilitates ORR kinetics through optimizing the adsorption of intermediates.

Chemistry↗
DOE OSTI2022

libwfa: Wavefunction analysis tools for excited and open‐shell electronic states

Abstract An open‐source software library for wavefunction analysis, libwfa, provides a comprehensive and flexible toolbox for post‐processing excited‐state calculations, featuring a hierarchy of interconnected visual and quantitative analysis methods. These tools afford compact graphical representations of various excited‐state processes, provide detailed insight into electronic structure, and are suitable for automated processing of large data sets. The analysis is based on reduced quantities, such as state and transition density matrices (DMs), and allows one to distill simple molecular orbital pictures of physical phenomena from intricate correlated wavefunctions. The implemented descriptors provide a rigorous link between many‐body wavefunctions and intuitive physical and chemical models, for example, exciton binding, double excitations, orbital relaxation, and polyradical character. A broad range of quantum‐chemical methods is interfaced with libwfa via a uniform interface layer in the form of DMs. This contribution reviews the structure of libwfa and highlights its capabilities by several representative use cases. This article is categorized under: Software > Quantum Chemistry Theoretical and Physical Chemistry > Spectroscopy

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

Measurements of L-shell X-ray emission lines of neonlike europium on an electron beam ion trap

We report a measurement of the two X–ray transitions that proceed from the (1 s 2 2 s 2 2 p 5 1/2 3 d 3/2 ) J = 1 and (1 s 2 2 s 1/2 2 p 6 3 p 1/2 ) J = 1 upper levels to the (1 s 2 2 s 2 2 p 6 ) J = 0 ground level in neonlike Eu 53+ ( Z = 63), that is, near the previously documented avoided crossing of the two upper levels at Z = 68. The measurement was carried out using the calorimeter spectrometer on the Livermore EBIT–I electron beam ion trap. Here, it affirms the trends set by the neighboring neonlike ions both in terms of the relative intensity of the two lines and in terms of the magnitude of disagreement with theoretical energy level predictions.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

Off-shell amplitudes as boundary integrals of analytically continued Wilson line slope

We consider a conformal complex singlet extension of the Standard Model with a Higgs portal interaction. The global U(1) symmetry of the complex singlet can be either broken or unbroken and we study each scenario. In the unbroken case, the global U(1) symmetry protects the complex singlet from decaying, leading to an ideal cold dark matter candidate with approximately 100 GeV mass along with a significant proportion of thermal relic dark matter abundance. In the broken case, we have developed a renormalization-scale optimization technique to significantly narrow the parameter space and in some situations, provide unique predictions for all the model’s couplings and masses. We have found there exists a second Higgs boson with a mass of approximately 550 GeV that mixes with the known 125 GeV Higgs with a large mixing angle sin θ ≈ 0.47 consistent with current experimental limits. The imaginary part of the complex singlet in the broken case could provide axion dark matter for a wide range of models. Upon including interactions of the complex scalar with an additional vector-like fermion, we explore the possibility of a diphoton excess in both the unbroken and the broken cases. In the unbroken case, the model can provide a natural explanation for diphoton excess if extra terms are introduced providing extra contributions to the singlet mass. In the broken case, we find a set of coupling solutions that yield a second Higgs boson of mass 720 GeV and an 830 GeV extra vector-like fermion F , which is able to address the 750 GeV LHC diphoton excess. We also provide criteria to determine the symmetry breaking pattern in both the Higgs and hidden sectors.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

All-order celestial OPE from on-shell recursion

We determine tree level, all-order celestial operator product expansions (OPEs) of gluons and gravitons in the maximally helicity violating (MHV) sector. We start by obtaining the all-order collinear expansions of MHV amplitudes using the inverse soft recursion relations that they satisfy. These collinear expansions are recast as celestial OPE expansions in bases of momentum as well as boost eigenstates. This shows that inverse soft recursion for MHV amplitudes is dual to OPE recursion in celestial conformal field theory.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

The Magnetic Properties of the Spin-1 Ising Fullerene Cage with a Core-Shell Structure

Magnetic properties of Ising-type endohedral fullerene (IEF), which are formed by an atom encapsulated inside a diluted magnetic spherical cage, have been investigated theoretically as a function of its system parameters, and magnetism calculations by using effective field theory (EFT) were performed. Theoretical studies have been carried out to understand the effect on magnetic behaviors by the diluted magnetic surface, crystal field, and exchange couplings. The results display the first second-order phase transitions and tricritical point. The reentrant phenomena have been observed within a certain parameter range.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗