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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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7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on VSb(SeO3)4 by Materials Project

VSb(SeO3)4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. V5+ is bonded in an octahedral geometry to six O2- atoms. There are four shorter (2.03 Å) and two longer (2.06 Å) V–O bond lengths. Sb5+ is bonded in an octahedral geometry to six O2- atoms. There are two shorter (2.00 Å) and four longer (2.03 Å) Sb–O bond lengths. There are two inequivalent Se+3.50+ sites. In the first Se+3.50+ site, Se+3.50+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. There is two shorter (1.70 Å) and one longer (1.82 Å) Se–O bond length. In the second Se+3.50+ site, Se+3.50+ is bonded in a distorted T-shaped geometry to three O2- atoms. There is one shorter (1.69 Å) and two longer (1.78 Å) Se–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to one V5+ and one Se+3.50+ atom. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to one Sb5+ and one Se+3.50+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one Sb5+ and one Se+3.50+ atom. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to one V5+ and one Se+3.50+ atom. In the fifth O2- site, O2- is bonded in a bent 120 degrees geometry to one Sb5+ and one Se+3.50+ atom. In the sixth O2- site, O2- is bonded in a bent 120 degrees geometry to one V5+ and one Se+3.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Structure and magnetism in epitaxial Fe 1 + x VSb nanocomposite films

The combination of ferromagnetism and semiconducting behavior offers an avenue for realizing novel spintronics and spin-enhanced thermoelectrics. Here we demonstrate the synthesis of doped and nanocomposite half-Heusler Fe 1+x VSb films by molecular beam epitaxy. For dilute excess Fe (x < 0.1), we observe a decrease in the Hall electron concentration and no secondary phases in x-ray diffraction. Magnetotransport measurements suggest weak ferromagnetism that onsets at a temperature of T c ≈ 5 K. For higher Fe content (x > 0.1), ferromagnetic Fe nanostructures precipitate from the semiconducting FeVSb matrix. The Fe/FeVSb interfaces are epitaxial, as observed by transmission electron microscopy and x-ray diffraction. Further, magnetotransport measurements suggest proximity-induced magnetism in the FeVSb from the Fe/FeVSb interfaces, or superparamagnetically coupled Fe-rich clusters, at an onset temperature of T c ≈ 20 K.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Materials Data on VSb by Materials Project

SbV is Molybdenum Carbide MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. V3+ is bonded to six equivalent Sb3- atoms to form a mixture of edge, face, and corner-sharing VSb6 octahedra. The corner-sharing octahedral tilt angles are 51°. All V–Sb bond lengths are 2.77 Å. Sb3- is bonded in a 6-coordinate geometry to six equivalent V3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VSb(PO4)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2024

Controlling Vibronic Coupling in Chlorophyll Proteins: The Effects of Excitonic Delocalization and Vibrational Localization

Vibrational-electronic (vibronic) coupling plays a critical role in excitation energy transfer in molecular aggregates and pigment-protein complexes (PPCs). But the interplay between excitonic delocalization and vibronic interactions is complex, often leaving even qualitative questions as to what conceptual framework (e.g., Redfield versus Forster theory) should be used to interpret experimental results. To shed light on this issue, we report here on the interplay between excitonic delocalization and vibronic coupling in site-directed mutants of the water soluble chlorophyll protein (WSCP), as reflected in 77 K fluorescence spectra. Experimentally, we find that in PPCs where excitonic delocalization is disrupted (either by mutagenesis or heterodimer formation), the relative intensity of the vibrational sideband (VSB) in fluorescence spectra is suppressed by up to 37% compared to the native protein. Furthermore, numerical simulations reveal that this effect results from the localization of high-frequency vibrations in the coupled system; while excitonic delocalization suppresses the purely electronic transition due to H-aggregate-like dipole-dipole interference, high-frequency vibrations are unaffected, leading to a relative enhancement of the VSB. By comparing VSB intensities of PPCs both in the presence and absence of excitonic delocalization, we extract a set of “local” Huang-Rhys (HR) factors for Chl a in WSCP. More generally, our results suggest a significant role for geometric effects in controlling energy-transfer rates (which depend sensitively on absorption/fluorescence line shapes) in molecular aggregates and PPCs.

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

Comparison of biofuel life-cycle GHG emissions assessment tools: The case studies of ethanol produced from sugarcane, corn, and wheat

The use of alternative fuels, particularly bio-based fuels, has been an important strategy to achieve greenhouse gas (GHG) emission reductions compared to petroleum-based fuels. However, discrepancies between results obtained by using different attributional life-cycle assessment (LCA) tools have challenged the credibility of the individual assessments, and as result, the progress towards or compliance with GHG mitigation targets. The objective of this study was to identify the main differences and commonalities in methodological structures, calculation procedures, and assumptions for the major commercial biofuel, ethanol, across three public LCA tools, BioGrace (EU), GHGenius (Canada), and GREET (U.S.), and a research-oriented fourth, the Virtual Sugarcane Biorefinery (VSB), a Brazilian platform for sugarcane ethanol assessments. The calculated emissions across models ranged from 16 to 45 for sugarcane, 43-62 for corn, and 45-68 g CO 2 eq MJ -1 for wheat ethanol. Harmonizing the three public models with VSB assumptions for sugarcane ethanol produced in Brazil, the range was reduced to 16-17 g CO 2 eq MJ -1 for sugarcane ethanol. Agricultural production (e.g., N 2 O emissions from fertilizers; energy and fuel use; straw field-burning; and limestone application) and ethanol shipping were found to be the major causes for variations for differences calculated for sugarcane ethanol. Similarly, harmonizing BioGrace and GHGenius calculations using GREET assumptions for U.S. corn ethanol generated nearly identical results (models varied within a 3% range). The coproduct treatment method was found to be the most influential parameter in the variations calculated for both corn and wheat ethanol. The application of the tools as part of GHG emissions accounting requirements is often defined via regulations and differences and/or conflicting assumptions set-forth in these models lead to most differences observed. Our study provides recommendations for promoting transparency in LCA calculations and assumptions across the tools used in research and development or for regulatory tools regarding biofuels.

09 BIOMASS FUELS↗