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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 1,477 records · Page 82
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Hydrogen diffusion and electronic structure in crystalline and amorphous Ti/sub y/CuH/sub x/

Hydrogen diffusion behavior and electronic properties of crystalline TiCuHo94, Ti2CuH1.90, and Ti2CuH2.63 and amorphous a-TiCuH1.4 were studied using proton relaxation times, proton Knight shifts, and magnetic susceptibilities. Crystal structure and hydrogen site occupancy have major roles in hydrogen mobility. The density of electron states at E sub F is reduced in amorphous a-TiCuH1.4 compared to the crystalline hydrides.

Bowman, R. C., Jr.↗
DOE OSTI2014

Quasiparticle electronic structure and optical absorption of diamond nanoparticles from ab initio many-body perturbation theory

The excited states of small-diameter diamond nanoparticles in the gas phase are studied using the GW method and Bethe-Salpeter equation (BSE) within the ab initio many-body perturbation theory. The calculated ionization potentials and optical gaps are in agreement with experimental results, with the average error about 0.2 eV. The electron affinity is negative and the lowest unoccupied molecular orbital is rather delocalized. Precise determination of the electron affinity requires one to take the off-diagonal matrix elements of the self-energy operator into account in the GW calculation. BSE calculations predict a large exciton binding energy which is an order of magnitude larger than that in the bulk diamond.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Electronic structure, dimer physics, orbital-selective behavior, and magnetic tendencies in the bilayer nickelate superconductor $\mathrm{La_3Ni_2O_7}$under pressure

Motivated by the recently reported high-temperature superconductivity in the bilayer La 3 Ni 2 O 7 (LNO) under pressure, we comprehensively study this system using ab initio techniques. The Ni 3d orbitals have a large bandwidth at ambient pressure, increasing by ~22% at 29.5 GPa. Without electronic interactions, the Ni d 3z 2 -r 2 orbitals form a bonding-antibonding molecular orbital state via the O p z inducing a “dimer” lattice in the LNO bilayers. The Fermi surface consists of two-electron sheets with mixed e g orbitals and a hole pocket defined by the d 3z 2 -r 2 orbital, suggesting a Ni two-orbital minimum model. Different from the infinite-layer nickelate, we obtained a large interorbital hopping between d 3z 2 -r 2 and d x 2 -y 2 states in LNO, caused by the ligand “bridge” of in-plane O p x or p y orbitals connecting those two orbitals, inducing d-p σ-bonding characteristics. The competition between the intraorbital and interorbital hoppings leads to an interesting dominant spin stripe (π,0) order because of bond ferromagnetic tendencies via the recently discussed “half-empty” mechanism.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

The electronic structure of an S-pair in barrier-less metal/silicon junctions

With S atoms doping into a bulk Si, it is revealed through first principles calculations that the highly S concentrated bulk Si is metallic. S atoms can be highly doped in the bulk Si because an S-pair located face to face in adjacent Si lattice sites gains a large energy and forms sp{sup 2} + p{sub z} electronic configurations and extra donor electrons. Schottky junction will be thus barrier-less by the Si metallization, well agreeing with experimental analyses.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2011

Electronic Structure Studies of 200 MeV Ag{sup +15} Swift Heavy Ion Irradiated SnO{sub 2} Thin Films Using X-Ray Absorption Spectroscopy

Tin dioxide (SnO{sub 2}) thin films were deposited on a well cleaned sapphire single crystal substrate by rf magnetron sputtering technique. After deposition, films were irradiated by swift heavy ion (SHI) irradiation at various ion fluences. We present the X-ray absorption spectra (XAS) at the oxygen K- and Sn M{sub 5,4,} edge. The XAS pattern reveals the broadening of O K- and Sn M{sub 5,4,} edge features with increasing ion fluence. The fraction of under-coordinated surface atoms in the SnO{sub 2} thin films increases, which is attributed to the structural distortions induced by SHI irradiations.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Tuning the electronic structure of Ag-Pd alloys to enhance performance for alkaline oxygen reduction

Alloying is a powerful tool that can improve the electrocatalytic performance and viability of diverse electrochemical renewable energy technologies. Herein, we enhance the activity of Pd-based electrocatalysts via Ag-Pd alloying while simultaneously lowering precious metal content in a broad-range compositional study focusing on highly comparable Ag-Pd thin films synthesized systematically via electron-beam physical vapor co-deposition. Cyclic voltammetry in 0.1 M KOH shows enhancements across a wide range of alloys; even slight alloying with Ag (e.g. Ag 0.1 Pd 0.9 ) leads to intrinsic activity enhancements up to 5-fold at 0.9 V vs. RHE compared to pure Pd. Based on density functional theory and x-ray absorption, we hypothesize that these enhancements arise mainly from ligand effects that optimize adsorbate–metal binding energies with enhanced Ag-Pd hybridization. This work shows the versatility of coupled experimental-theoretical methods in designing materials with specific and tunable properties and aids the development of highly active electrocatalysts with decreased precious-metal content.

25 ENERGY STORAGE↗
DOE OSTI2011

Electronic structure studies of Fe doped CeO{sub 2} thin films by resonance photoemission spectroscopy

We have studied the modification in the electronic properties of pulsed laser deposited CeO{sub 2} thin films due to Fe doping (2 and 6 at %), with the help of x-ray photoemission spectroscopy (XPS) and resonance photoemission spectroscopy (RPES) measurements. XPS results indicate the ionic state of Fe in the Fe doped films, ruling out the possibility of Fe metallic clusters. Valence band spectra of CeO{sub 2} show an additional feature after Fe doping, suggesting its incorporation in the CeO{sub 2} matrix. RPES studies on these films reveal the hybridization between oxygen vacancy induced Ce localized states and Fe derived states.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Theoretical investigation of the atomic and electronic structure of Li{sub x}BC{sub 3} intercalated compounds

Li{sub x}BC{sub 3} intercalated compounds with various configurations are studied for their possible application as electrode materials for lithium current sources. For this purpose, the band structure and the density of states were calculated for each structure, and energy stability and possible deformations due to a change in the unit cell volume during intercalation are investigated.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

First principles study of the electronic structure of the Ni 2 MnIn / InAs and Ti 2 MnIn / InSb interfaces

We present a first principles study of the electronic and magnetic properties of epitaxial interfaces between the Heusler compounds, Ti 2 MnIn and Ni 2 MnIn, and the III-V semiconductors, InSb and InAs, respectively. We use density functional theory (DFT) with a machine-learned Hubbard U correction determined by Bayesian optimization. Here, we evaluate these interfaces for prospective applications in Majorana-based quantum computing and spintronics. In both interfaces, states from the Heusler penetrate into the gap of the semiconductor, decaying within a few atomic layers. The magnetic interactions at the interface are weak and local in space and energy. Magnetic moments of less than 0.1 µB are induced in the two atomic layers closest to the interface. The induced spin polarization around the Fermi level of the semiconductor decays within a few atomic layers. The decisive factor for the induced spin polarization around the Fermi level of the semiconductor is the spin polarization around the Fermi level in the Heusler, rather than the overall magnetic moment. As a result, the ferrimagnetic narrow-gap semiconductor Ti 2 MnIn induces a more significant spin polarization in the InSb than the ferromagnetic metal Ni 2 MnIn induces in the InAs. This is explained by the position of the transition metal d states in the Heusler with respect to the Fermi level. Based on our results, these interfaces are unlikely to be useful for Majorana devices but could be of interest for spintronics.

36 MATERIALS SCIENCE↗