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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Verifying the reciprocity of interparticle interaction forces in strongly coupled systems

We propose a simple criterion for revealing the breaking of pair interaction symmetry in strongly coupled dissipative systems. The criterion is based on the analysis of correlations between the velocities of strongly interacting particles, which can be measured relatively easily in experiments with macroparticles in various media. We derive analytic relations that make it possible to calculate the derivatives of the interaction force between a pair of particles from the data on the correlations of their velocities and coordinates. The proposed criterion and relations are verified using the results of numerical simulation of the dynamics of dust particles in a plasma.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Role of vertex corrections in the matrix formulation of the random phase approximation for the multiorbital Hubbard model

In the framework of a multiorbital Hubbard model description of superconductivity, a matrix formulation of the superconducting pairing interaction that has been widely used is designed to treat spin, charge, and orbital fluctuations within a random phase approximation (RPA). In terms of Feynman diagrams, this takes into account particle-hole ladder and bubble contributions as expected. It turns out, however, that this matrix formulation also generates additional terms which have the diagrammatic structure of vertex corrections. Furthermore we examine these terms and discuss the relationship between the matrix-RPA superconducting pairing interaction and the Feynman diagrams that it sums.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Influence of soluble oligomeric aluminum on precipitation in the Al-KOH-H2O system

The role of oligomeric aluminate (Al(OH)4-) species in the precipitation of aluminum phases such as gibbsite (a-Al(OH)3) from aqueous hydroxide solutions remains unclear and difficult to probe directly, despite its importance to developing accurate predictions of Al solubility in highly alkaline systems. Precipitation in this system entails a transition from predominantly tetrahedrally coordinated Al species in solution to octahedrally coordinated Al in gibbsite. Here we report a quantitative study of dissolved Al in the Al-KOH-H2O system using a combination of molecular spectroscopies. We established a relationship between changes in 27Al NMR chemical shifts and the relative intensity of Raman vibrational bands, indicative of variations in the ensemble speciation of Al in solution, and the formation of unique contact ion pair interactions with the aluminate dimer, Al2O(OH)62 . A strong correlation between the extent of Al oligomerization and the amount of solvated Al was demonstrated by systematically varying the KOH:Al molar ratio. The concentration of dissolved oligomeric Al in solution also directly impacted the particle size and morphology of gibbsite; high concentrations of dimeric Al2O(OH)62-, yielded smaller and more numerous anhedral to subhedral gibbsite particles, while low concentrations yielded fewer and larger euhedral gibbsite platelets. The collective observations suggest a key role of the Al2O(OH)62- dimer in promoting gibbsite precipitation from solution, where the potassium ion-paired dimer possibly catalyzes a more rapid transformation of Al coordination from tetrahedral in solution to octahedral in gibbsite.

Dembowski, Mateusz↗
DOE OSTI2021

Diversifying Composition Leads to Hierarchical Composites with Design Flexibility and Structural Fidelity

Although significant progress has been made in the self-assembly of nanostructures, present successes heavily rely on precision in building block design, composition, and pair interactions. These requirements fundamentally limit our ability to synthesize macroscopic materials where the likelihood of impurity inclusion escalates and, more importantly, to access molecular-to-nanoscopic-to-microscopic-to-macroscopic hierarchies, since the types and compositions of building blocks vary at each stage. Inspired by biological blends and high-entropy alloys, we hypothesize that diversifying the blend’s composition can overcome these limitations. Increasing the number of components increases mixing entropy, leading to the dispersion of different components and, as a result, enhances interphase miscibility, weakens the dependence on specific pair interactions, and enables long-range cooperativity. This hypothesis is validated in complex blends containing small molecules, block copolymer-based supramolecules, and nanoparticles/colloidal particles. Hierarchically structured composites can be obtained with formulation flexibility in the filler selection and blend composition. It is worth noting that, by adding small molecules, we can solve the size constraint that plagues traditional block copolymer/nanoparticle blends. Detailed characterization and simulation further confirm that each component is distributed to locally mediate unfavorable interactions, cooperatively mitigate composition fluctuations, and retain structural fidelity. Furthermore, the blends have sufficient mobility to access tunable microstructures without compromising the order of the nanostructure. Besides establishing a kinetically viable pathway to release current constraints in the composite design and to navigate uncertainties during structure formation over multiple length scales, the present study demonstrates that entropy-driven behaviors can be realized in systems beyond high-entropy alloys despite inherent differences between metal alloys and organic/inorganic hybrids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1989

An infrared study of starbursts in the interacting galaxy pair Arp 299 (NGC 3690+IC 694)

Extensive infrared observations have been obtained of the three active regions in Arp 299. Multiaperture JHK photometry reveals that the colors of the three regions are totally different from each other, and that there are very red nuclei smaller than 4 arcsec in two of them. Multiaperture spectroscopy of the Br-gamma and the shock-excited H2 lines shows that both the atomic and molecular lines are spatially extended, indicating that Arp 299 is undergoing an active episode of star formation not only in its nuclei but also well outside of them. Although there is some evidence that suggests the presence of a compact, active galactic nucleus, a simple starburst model can explain the bolometric luminosities, production rates of ionizing photons, and H24 line luminosities of each active region in Arp 299. However, each starburst cannot last longer than 10 to the 8th yr.

Nakagawa, Takao↗
DOE OSTI2019

Energy of Phonons and Zero-Point Vibrations in Compressed Rare-Gas Crystals

A dynamic matrix of rare-gas crystals is constructed within the model of deformable and polarizable atoms based on the nonempirical short-range repulsion potential taking into account the three-body interaction and deformation of electron shells of dipole-type atoms within the pair and three-body approximations. Ab initio calculations of the phonon energy for compressed rare-gas crystals are performed at two and ten mean-value points of the Chadi–Kohen method in a wide pressure range. It is shown that the contribution of three-body forces to the phonon frequencies due to overlap of electron shells of neighboring atoms is small as compared to the pair interaction even at a high pressure and most pronounced for Xe. The contributions of the deformation of electron shells within the pair and three-body approximations differ for different mean-value points and increase with an increase in pressure. The zero-point energies calculated by the Chadi–Kohen method for crystals of the Ne–Xe series are compared with the known experimental data at p = 0 and calculation results obtained by other researchers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Particle- γ coincidence spectroscopy of the N = 90 nucleus 154 Gd by ( p,tγ )

A segmented Si-telescope and HPGe array, STARS-LIBERACE, was used to study the 156 Gd(p, tγ) 154 Gd direct reaction by particle- γ coincidence spectroscopy. New cross sections with a 25MeV proton beam are reported and compared to previous (p,t) and (t,p) studies. Furthermore, additional evidence for coexisting K π =0$_1^+$,2$_1^+$ and 0$_2^+$, 2$_2^+$ configurations at N = 90 is presented. Direct and indirect population patterns of the low-lying states are also explored. Review of the new and existing evidence favors an interpretation based on a configuration-dependent pairing interaction. The weakening of monopole pairing strength and an increase in quadrupole pairing strength could bring 2p-2h 0 + states below 2 Δ. This may account for a large number of the low-lying 0 + states observed in two-nucleon transfer reactions. A hypothesis for the origin of the 0$_2^+$ and 0$_3^+$ states is provided.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Dynamic Potential of Interaction between Nitrogen Atoms and Aluminum Crystal Surface

Specific features of the angular distributions of accelerated neutral nitrogen atoms at the grazing angles of incidence on the Al(001) crystal surface have been investigated by the computer simulation method. The N–Al pair interaction potential is approximated by the three-parameter Morse potential with the energy dependent coefficients. The angular distributions of scattered atoms have been simulated taking into account the interaction between atoms and several atomic layers in the lattice and the atomic displacement during thermal oscillations. The parameters of the pair potential of accelerated neutral nitrogen atoms in the energy range from 10 to 70 keV have been determined according to the best agreement between the calculated dependence of the rainbow scattering angle on the energy of particles incident on the crystal surface and the available experimental data.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Interaction of macroparticles localized in Wigner–Seitz cells of various types of cubic lattices in an equilibrium plasma

The interaction of two charged point macroparticles located in Wigner–Seitz cells of simple cubic (SC), body-centered cubic (BCC), or face-centered cubic (FCC) lattices in an equilibrium plasma has been studied within the Debye approximation or, more specifically, based on the linearized Poisson–Boltzmann model. The shape of the outer boundary is shown to exert a strong influence on the pattern of electrostatic interaction between the two macroparticles, which transforms from repulsion at small interparticle distances to attraction as the interparticle distance approaches half the length of the computational cell. The macroparticle pair interaction potential in an equilibrium plasma is shown to be nevertheless the Debye one and purely repulsive for likely charged macroparticles.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

A first principles study on the adsorbate-adsorbate interactions on the CdTe(111) surface with Cd, Te, Zn, and Se adatoms

The study of adsorbate-adsorbate interactions is essential to understanding early crystal growth dynamics. Here, we employ planewave density functional theory to study the binary adatom pair interactions between Cd-Cd, Te-Te, Zn-Zn, Se-Se, Cd-Te, Cd-Se, Cd-Zn, Te-Se, Te-Zn, and Se-Zn adatom pairs on two CdTe(111) surfaces. An analysis of the interaction energies between binary adatom pairs suggests repulsive interactions are common regardless of the relative distance between adatoms. For the CdTe(111)A surface, attractive interactions occur between neighboring chalcogen (i.e., Te and Se) and Group 12 (i.e., Cd and Zn) adatom pairs. For the CdTe(111)B surface, attractive interactions occur between neighboring Group 12 adatoms forming a surface dimer configuration. Furthermore, the formation energy of an adatom pair is decomposed in terms of the electronic, elastic, and adatom binding contributions. For smaller interatomic distances between the adatoms, the formation energy is primarily a function of the electronic interactions, with null contributions from the elastic and adatom binding interactions for Group 12-containing pairs. Because of the less favorable electronic interactions for larger interatomic distances between the adatoms, the formation energies are typically more positive. Lastly, neighboring adatoms significantly increase the barriers of migration on the CdTe(111)A surface relative to unary adatoms for the top-to-fcc and fcc-to-fcc sites, while the migration barriers on the CdTe(111)B surface only increases for the fcc-to-fcc migration of chalcogen species. From this analysis, we illustrate the role of adatom interactions during the early stages of the surface nucleation processes on CdTe(111) thin films.

CdTe↗
DOE OSTI2022

Superconductivity in multiorbital systems with repulsive interactions: Hund's pairing versus spin-fluctuation pairing

Hund's pairing refers to Cooper pairing generated by onsite interactions that become attractive due to large Hund's exchange J. This is possible in multiorbital systems even when all local bare interactions are repulsive, since attractions in specific channels are given by certain linear combinations of interaction parameters. On the other hand, pairing processes such as the exchange of spin fluctuations are also present. We compare mean-field Hund's pairing and spin-fluctuation-mediated pairing using electronic bands appropriate for different classes of multiorbital systems over a wide range of interaction parameters. We find that, for systems without clear nesting features, the superconducting state generated by the Hund's mechanism agrees well with that from the full fluctuation exchange vertex when Hund's exchange and spin-orbit coupling are sufficiently large. On the other hand, for systems characterized by a peaked finite-momentum particle-hole susceptibility, spin-fluctuation pairing generally dominates over Hund's pairing. From this perspective Hund's pairing states appear unlikely to be realized in systems like Sr 2 RuO 4 and generic iron-based superconductors.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Dynamical interactions of galaxy pairs

Here the author briefly reviews the dynamics of sinking satellites and the effect of companions on elliptical galaxies. The author then discusses recent work on interacting disk systems, and finally focuses on a favorite interacting pair, NGC 5194/5195.

Athanassoula, E.↗
DOE OSTI2019

{sup 125}Te-NMR Study in Novel Superconductor Pb{sub 1−x}Tl{sub x}Te with Valence Skipping Dopants

Pb{sub 1−x}Tl{sub x}Te is an anomalous low carrier density superconductor for which the origin of the superconductivity is not understood. Thallium is the only dopant to cause superconductivity in PbTe, suggesting that these specific impurities have a unique effect on the electronic states. Systematic {sup 125}Te-NMR studies on single-crystallines Pb{sub 1−x}Tl{sub x}Te (x = 0, 0.35, 1.0 at%) reveal that the Tl dopants induce spatially inhomogeneous electronic states around the Tl dopants. In the superconducting sample at x = 1.0 at%, {sup 125}Te nuclear spin relaxation rate (1/T{sub 1}T) in the vicinity of the Tl dopants is unexpectedly enhanced below ∼10 K. This coincides with the temperature below which the resistivity exhibits an upturn. By contrast, such anomalies were not detected in the non-superconducting sample at x = 0.35 at%. These observations can be consistently explained by charge Kondo effect, in which two nearly degenerate valence states of the Tl dopant form a resonating valence state upon cooling below 10 K. Based on these observations, we suggest that the coherent hopping of 6s-electron pair may provide the pairing interaction (i.e., a negative-U scenario), leading to the anomalously high T{sub c} found for Pb{sub 1−x}Tl{sub x}Te.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Density Functional Theory Study on Electronic Structures and Magnetism for Nitrogen-Doped ZnS

Using the full-potential linearized augmented plane wave method, together with the generalized gradient approximation and modified Becke-Johnson as correlation potential, the electronic structures and magnetism for nitrogen-doped ZnS are investigated. Based on the generalized gradient approximation, calculations show nitrogen-substituting sulfur (N{sub S}) would induce the ZnS to be paramagnetic metal. As the band gap increasing to the experimental results (obtained by the modified Becke-Johnson potential), the N{sub S} defects would induce the ZnS to be a ferromagnetic metal. The total magnetic moment for ZnS supercell with single N{sub S} defect is 0.85 μ{sub B}. Positive chemical pair interactions imply that N{sub S} defects would form homogeneous distribution in ZnS host. Sulfur vacancies would give rise to the ZnS with N{sub S} defects system losing the magnetism. Moderate formation energy (0.71 eV) indicates ZnS with N{sub S} defects could be fabricated experimentally.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Absence of Dobrushin States for 2d Long-Range Ising Models

We consider the two-dimensional Ising model with long-range pair interactions of the form J{sub xy}∼|x−y|{sup −α} with α>2, mostly when J{sub xy}≥0. We show that Dobrushin states (i.e. extremal non-translation-invariant Gibbs states selected by mixed ± boundary conditions) do not exist. We discuss possible extensions of this result in the direction of the Aizenman–Higuchi theorem, or concerning fluctuations of interfaces. We also mention the existence of rigid interfaces in two long-range anisotropic contexts.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1996

Electrohydrodynamic Interaction of a Pair of Spherical Drops

The axisymmetric electrohydrodynamic interaction between two spherical emulsion drops has been examined, using the leaky dielectric model to represent the constitutive behavior of the liquid phases. The results follow from the general solutions in bispherical coordinates to the Laplace equation for the electric potential and the Stokes equations for the velocity field. For drops of similar composition, the electrical interactions induced between the drops by the imposition of the electric field are always attractive, meaning they favor coalescence of the drop pair. The hydrodynamic interactions, however, are not always favorable and, indeed, are shown in certain circumstances to drive the drops apart.

Erker, J. A.↗