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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on NaGa(H2N)4 by Materials Project

NaGa(NH2)4 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of two NaGa(NH2)4 sheets oriented in the (0, 0, 1) direction. Na1+ is bonded in a 4-coordinate geometry to three N3- and one H1+ atom. There are a spread of Na–N bond distances ranging from 2.37–2.42 Å. The Na–H bond length is 2.58 Å. Ga3+ is bonded in a tetrahedral geometry to four N3- atoms. There are a spread of Ga–N bond distances ranging from 1.93–1.96 Å. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted water-like geometry to one Na1+, one Ga3+, and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the second N3- site, N3- is bonded in a distorted trigonal non-coplanar geometry to one Ga3+ and two H1+ atoms. Both N–H bond lengths are 1.02 Å. In the third N3- site, N3- is bonded in a 4-coordinate geometry to one Na1+, one Ga3+, and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the fourth N3- site, N3- is bonded in a distorted water-like geometry to one Na1+, one Ga3+, and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. There are eight inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one Na1+ and one N3- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaGa(SiO3)2 by Materials Project

NaGa(SiO3)2 is Esseneite structured and crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Na1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.41–2.84 Å. Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with six equivalent SiO4 tetrahedra and edges with two equivalent GaO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.94–2.12 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent GaO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–60°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Na1+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+, one Ga3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two equivalent Ga3+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaGa(GeO3)2 by Materials Project

NaGa(GeO3)2 is Esseneite structured and crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Na1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.43–2.83 Å. Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with six equivalent GeO4 tetrahedra and edges with two equivalent GaO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.95–2.11 Å. Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with three equivalent GaO6 octahedra and corners with two equivalent GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 40–62°. There are a spread of Ge–O bond distances ranging from 1.74–1.79 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+, one Ga3+, and one Ge4+ atom. In the second O2- site, O2- is bonded to one Na1+, two equivalent Ga3+, and one Ge4+ atom to form a mixture of distorted corner and edge-sharing ONaGa2Ge tetrahedra. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Na1+ and two equivalent Ge4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaGa(SeO3)2 by Materials Project

NaGa(SeO3)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Na1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.53–2.83 Å. Ga3+ is bonded in an octahedral geometry to six O2- atoms. There are a spread of Ga–O bond distances ranging from 1.96–2.03 Å. There are two inequivalent Se4+ sites. In the first Se4+ site, Se4+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There is one shorter (1.72 Å) and two longer (1.73 Å) Se–O bond length. In the second Se4+ site, Se4+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. All Se–O bond lengths are 1.74 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Ga3+, and one Se4+ atom. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to one Ga3+ and one Se4+ atom. In the third O2- site, O2- is bonded to two equivalent Na1+, one Ga3+, and one Se4+ atom to form a mixture of distorted corner and edge-sharing ONa2GaSe tetrahedra. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Na1+, one Ga3+, and one Se4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaGa(H2N)4 by Materials Project

NaGaN3H5NHH2 crystallizes in the monoclinic P2_1/c space group. The structure is one-dimensional and consists of four ammonia molecules; four hydrogen molecules; and two NaGaN3H5 ribbons oriented in the (0, 1, 0) direction. In each NaGaN3H5 ribbon, Na1+ is bonded in a linear geometry to two N3- atoms. There are one shorter (2.25 Å) and one longer (2.33 Å) Na–N bond lengths. Ga3+ is bonded in a 3-coordinate geometry to three N3- atoms. There are a spread of Ga–N bond distances ranging from 1.79–2.31 Å. There are three inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted trigonal non-coplanar geometry to one Ga3+ and three H1+ atoms. All N–H bond lengths are 1.02 Å. In the second N3- site, N3- is bonded in a distorted single-bond geometry to one Na1+, one Ga3+, and one H1+ atom. The N–H bond length is 1.04 Å. In the third N3- site, N3- is bonded in a distorted trigonal non-coplanar geometry to one Na1+, one Ga3+, and one H1+ atom. The N–H bond length is 1.03 Å. There are five inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaGa by Materials Project

GaNa crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Na is bonded in a 5-coordinate geometry to five equivalent Ga atoms. There are two shorter (3.10 Å) and three longer (3.25 Å) Na–Ga bond lengths. Ga is bonded in a 7-coordinate geometry to five equivalent Na and two equivalent Ga atoms. Both Ga–Ga bond lengths are 2.42 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaGa by Materials Project

GaNa crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Na is bonded in a 7-coordinate geometry to five equivalent Ga atoms. There are a spread of Na–Ga bond distances ranging from 3.05–3.10 Å. Ga is bonded in a 7-coordinate geometry to five equivalent Na and two equivalent Ga atoms. Both Ga–Ga bond lengths are 2.72 Å.

36 MATERIALS SCIENCE↗
NASA NTRS1984

Coordination of Fe, Ga and Ge in high pressure glasses by Moessbauer, Raman and X-ray absorption spectroscopy, and geological implications

For some time, it has been recognized that the structure of silicate liquids has a great bearing on such magma properties as viscosity, diffusivity, and thermal expansion and on the extrapolation of thermodynamic quantities outside of the experimentally measurable range. In this connection it is vital to know if pressure imposes changes in melt structure similar to the pressure-induced reconstructive transformations in crystals. In the present study on 1 bar and high pressure glasses, an investigation is conducted regarding the coordination of Fe(3+) in Fe silicate glasses by Moessbauer spectroscopy. Raman spectroscopy is employed to explore the coordinations of Ge(4+) in GeO2 glasses and of Ga(3+) in NaGa silicate glasses, while the coordination of Ga(3+) in NaGaSiO4 glasses is studied with the aid of methods of X-ray absorption spectroscopy.

Fleet, M. E.↗
NASA NTRS1954

Experimental Permeability Measurements on a Strut-Supported Transpiration-Cooled Turbine Blade with Stainless-Steel Shell made by the Federal-Mogul Corporation under Bureau of Aeronautics Contract N0as 51613-C

A turbine blade with a porous stainless-steel shell sintered to a supporting steel strut has been fabricated for tests at the NACA by Federal-Mogul Corporation under contract from the Bureau of Aeronautics, Department of the Navy. The apparent permeability of this blade, on the average, more nearly approaches the values specified by the NAGA than did two strut-supported bronze blades in a previous investigation. Random variations of permeability in the present blade are substantialy greater than those of the bronze blades, but projected improvements in certain phases of the fabrication process are expected to reduce these variations.

Richards, Hadley T.↗
DOE OSTI2025

Volcano‐like Activity Trends in Au@Pd Catalysts: The Role of Pd Loading and Nanoparticle Size

The addition of palladium (Pd) to preformed gold nanoparticles (Au NPs) enables the formation of core‐shell structures with enhanced catalytic performance in oxidation reactions. However, predicting the precise palladium content required to achieve maximum catalytic activity remains difficult based on current understanding. Herein, Pd was systematically introduced onto titania‐supported Au NPs (2, 6, and 10 nm) to evaluate their performance in benzyl alcohol oxidation. A volcano‐like trend in catalytic activity was observed, where activity increased with Pd addition, peaked, and then declined. The Pd loading required for maximum activity depended on Au NP size: ≈40 at% Pd/Au for 2.6 nm, ≈20 at% Pd/Au for 6.4 nm, and ≈12.5 at% Pd/Au for 10.6 nm. For Au NPs > 6 nm, peak activity aligned with monolayer Pd coverage, while for smaller NPs (2–3 nm), optimal Pd content was below monolayer predictions. X‐ray absorption spectroscopy revealed a core‐shell structure at low Pd content, but higher Pd loadings led to Pd diffusion into the Au core. This structural transformation likely caused activity decline, indicating that AuPd alloying negatively impacts catalysis. These results highlight that core‐shell Au@Pd catalysts outperform AuPd alloys and provide crucial insights for designing highly active bimetallic catalysts.

X-ray absorption spectroscopy↗
DOE OSTI2022

Universally Accessible Structural Data on Macromolecular Conformation, Assembly, and Dynamics by Small Angle X-Ray Scattering for DNA Repair Insights.

Structures provide a critical breakthrough step for biological analyses, and small angle X-ray scattering (SAXS) is a powerful structural technique to study dynamic DNA repair proteins. As toxic and mutagenic repair intermediates need to be prevented from inadvertently harming the cell, DNA repair proteins often chaperone these intermediates through dynamic conformations, coordinated assemblies, and allosteric regulation. By measuring structural conformations in solution for both proteins, DNA, RNA, and their complexes, SAXS provides insight into initial DNA damage recognition, mechanisms for validation of their substrate, and pathway regulation. Here, we describe exemplary SAXS analyses of a DNA damage response protein spanning from what can be derived directly from the data to obtaining super resolution through the use of SAXS selection of atomic models. We outline strategies and tactics for practical SAXS data collection and analysis. Making these structural experiments in reach of any basic and clinical researchers who have protein, SAXS data can readily be collected at government-funded synchrotrons, typically at no cost for academic researchers. In addition to discussing how SAXS complements and enhances cryo-electron microscopy, X-ray crystallography, NMR, and computational modeling, we furthermore discuss taking advantage of recent advances in protein structure prediction in combination with SAXS analysis.

Chinnam, Naga Babu↗
DOE OSTI2026

Inertia estimation for power grids: A review of methods, challenges, and future prospects

The electric power grid is undergoing a significant transformation, shifting from traditional synchronous generators to inverter-based resources (IBRs) such as solar photovoltaics, wind turbines, and energy storage systems. This evolution leads to a reduction in system inertia, a critical attribute for maintaining frequency stability in response to disturbances. Consequently, the ability to monitor and estimate system inertia has become increasingly essential. This paper provides a comprehensive review of existing inertia estimation methodologies, analyzing them from multiple perspectives, including the types of data utilized, underlying estimation principles, operational modes, and system-wide applicability. A comparative summary table is included to distill commonalities and key characteristics across various studies. In addition, the paper examines practical implementations of inertia estimation across several major power systems worldwide, including the U.S. interconnections, the Nordic power system, and the U.K. grid. Key challenges are identified, particularly in estimating contributions from virtual inertia sources and load-induced inertia in increasingly converter-dominated networks. To address these emerging challenges, the paper proposes an integrated framework for real-time inertia estimation and monitoring. This framework encompasses critical components such as data acquisition, inertia estimation from both synchronous and non-synchronous sources, load-induced effects, optimization techniques, forecasting, and virtual inertia scheduling. Collectively, these elements enable dynamic, system-wide monitoring and adaptive control of grid inertia.

Inertia estimation↗
DOE OSTI2025

Be₂C as a neutron moderator for molten salt reactors: A first-principles study of structural, electronic, and defect properties

Beryllium carbide (Be 2 C), valued for its high neutron moderation efficiency and low absorption cross section, is a promising high-temperature neutron moderator for molten salt reactors. Its practical adoption, however, demands significant technological maturation, requiring comprehensive theoretical and experimental studies of its response to different conditions, including high temperature and irradiation. Here, we report initial results on the fundamental properties and radiation-induced defects of Be 2 C, focusing on antisites, vacancies, interstitial atoms, and Frenkel pairs in the Be and C sublattices. Using density functional theory (DFT) and ab initio molecular dynamics (AIMD), we calculate the defects formation and binding energies, evaluating their dependence on the supercell size, charge states, and chemical environment. In general, carbon defects exhibit higher formation energies, greater sensitivity to cell size, and stronger impacts on the density of states compared to beryllium defects, with charged state the effects being more pronounced. Static DFT reveals multiple metastable interstitial configurations, while AIMD identifies ground states as C-C <100> dumbbells and octahedral Be interstitials. In conclusion, the diversity of metastable configurations and defect states complicates the diffusion mechanisms, requiring further molecular dynamics analysis to elucidate the mechanisms and rates of radiation-induced atomic transport, as well as the structural stability of Be2C.

Ab initio modeling↗
DOE OSTI2021

Irradiation Damages of Structural Materials under Different Irradiation Environments

For the advancement and development of nuclear systems used in heavy irradiation environments such as fusion DEMO reactors, fission reactors, fast reactors, and accelerator driven target systems, it is necessary to fully understand the changes of mechanical properties and the other properties of the materials induced by irradiation and to clarify the synergistic effect of displacement damage and helium generation. In this study the mechanical property changes and microstructural development induce by displacement damage and helium production have been mainly examined in austenitic stainless steels, 316FR and type304, and ferritic/martensitic steel, HCM12A, irradiated at around 550oC in JRR-3M reactor and/or JOYO fast reactor. At 550°C, 316FR steel was superior to 304 steel in terms of the amount of ductility and strength with respect to irradiation resistance. It is noteworthy that at 550 °C as well as room temperature, the higher fracture strength of the 316FR steels is a remarkable result. It is found that helium atoms strongly influenced on creep lifetime of the irradiated austenitic stainless steel, 316FR. It was found that the ratio of creep rupture time is slightly lower than the lower limit of previous study’s Miyaji and co-workers in the region from 0.01 appm to 1 appm. It is also found that the lower limit of reduction ratio of creep rupture time (irradiation specimen to unirradiation one) does not decrease linearly with the helium production above 10 appm up to about 33 appm. dpa enhanced the reduction of creep lifetime. Recent R&D of high-energy accelerator driven target systems used under heavy irradiation environment is also introduced and discussed for high radiation resistance materials such as Ti alloys with very high number density of nano size precipitate, which have been studying under RaDIATE collaboration, from points of view of irradiation damage and materials development.

radiation damage, structural alloys, neutron irrad↗
DOE OSTI2024

Enhanced Strong-Field Ionization and Fragmentation of Methanol Using Noncommensurate Fields

Electron-initiated chemistry with chemically relevant electron energies (10–200 eV) is at the heart of several high-energy processes and phenomena. To probe these dissociation and fragmentation reactions with femtosecond resolution requires the use of femtosecond lasers to induce ionization of the polyatomic molecules via electron rescattering. Here, we combine noncommensurate fields with intensity-difference spectra using methanol as a model system. Experimentally, we find orders of magnitude enhancement in several product ions of methanol when comparing coherent vs incoherent combinations of noncommensurate fields. This approach not only mitigates multiphoton ionization and multicycle effects during ionization but also enhances tunnel ionization and electron rescattering energy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗