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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Na2FeCu(CN)6 by Materials Project

(Na)2FeCu(CN)6 is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is zero-dimensional and consists of four iron molecules, eight sodium molecules, and four Cu(CN)6 clusters. In each Cu(CN)6 cluster, Cu1+ is bonded in an octahedral geometry to six equivalent N3- atoms. All Cu–N bond lengths are 2.08 Å. C2+ is bonded in a distorted single-bond geometry to one N3- atom. The C–N bond length is 1.18 Å. N3- is bonded in a linear geometry to one Cu1+ and one C2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaSi2W2O5 by Materials Project

NaNaSi4(W2O5)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional and consists of four sodium molecules and one NaSi4(W2O5)2 framework. In the NaSi4(W2O5)2 framework, Na1+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. There are a spread of Na–O bond distances ranging from 2.29–2.54 Å. There are four inequivalent W+4.50+ sites. In the first W+4.50+ site, W+4.50+ is bonded in a bent 150 degrees geometry to two O2- atoms. There are one shorter (2.05 Å) and one longer (2.19 Å) W–O bond lengths. In the second W+4.50+ site, W+4.50+ is bonded in a linear geometry to two O2- atoms. There are one shorter (2.17 Å) and one longer (2.30 Å) W–O bond lengths. In the third W+4.50+ site, W+4.50+ is bonded in a single-bond geometry to one O2- atom. The W–O bond length is 2.14 Å. In the fourth W+4.50+ site, W+4.50+ is bonded in a single-bond geometry to one O2- atom. The W–O bond length is 2.20 Å. There are four inequivalent Si sites. In the first Si site, Si is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.65 Å. In the second Si site, Si is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.64 Å. In the third Si site, Si is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.60–1.65 Å. In the fourth Si site, Si is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.64 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one W+4.50+, and one Si atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Na1+, one W+4.50+, and one Si atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two Si atoms. In the fourth O2- site, O2- is bonded in a linear geometry to two Si atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si atoms. In the sixth O2- site, O2- is bonded in a linear geometry to two Si atoms. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two W+4.50+, and one Si atom. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si atoms. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si atoms. In the tenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two W+4.50+ and one Si atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Small-scale Assessment of Simplified Ceramic Waste Form Processing

The feasibility of directly processing glass-bonded sodalite ceramic waste form materials by heating a mixture of Zeolite 4A, chloride salt, and sodium borosilicate binder glass was demonstrated by generating laboratory-scale materials. This direct processing method eliminates pre-setting the moisture content of the Zeolite 4A, eliminates the step of occluding salt in the prepared Zeolite 4A prior to processing, and can be conducted using larger particle sizes of crushed Zeolite 4A and crushed borosilicate glass than those called for in the current method. These simplifications are expected to facilitate material transfer and handling in a hot cell or controlled atmosphere environment and be more readily implemented at large scale than the current method. Most materials made to assess these simplifications were directly processed at 925 °C for two hours in an argon atmosphere glovebox, but one material was processed at 925 °C for four hours and one material was processed at 880 °C for two hours. Sodalite was generated and became microencapsulated by the binder glass in all materials. The microstructures were uniform throughout each product, were similar in all products, and were similar to the microstructures of materials made previously using the pressureless consolidation or hot isostatic pressing methods. Various formulations showed the efficiency of sodalite generation was not sensitive to the salt-to-Zeolite 4A ratio or salt-to-glass mass ratio, although a greater relative mass of glass is required to encapsulate sodalite generated from large particles of aggregated Zeolite 4A. The upper limit of salt loadings that can be effectively processed remains to be determined. The effectiveness of direct processing provided new insights into the conversion mechanism. The salt was likely dissolved into the glass that transported NaCl into the Zeolite 4A aggregates and sodalite was generated in situ as NaCl migrated from the outside of the aggregate inward. Other salt cations (e.g., potassium, strontium, cesium, and probably lithium) remain dissolved in the glass encapsulating the zeolite/sodalite domains. When the glass solidifies during cooling, small halite inclusion phases form in glass within sodalite domains and large mixed salt inclusions form in glass surrounding the sodalite due to the low solubility of chloride in the (solid) glass. Other salt cations were oxidized during processing and formed inclusions in the bulk glass (e.g., neodymium). Initial degradation tests show the dissolution behavior of directly processed CWF (SCWF) materials is similar to CWF materials made using different methods.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Catalytic N–H Bond Formation Promoted by a Ruthenium Hydride Complex Bearing a Redox-Active Pyrimidine-Imine Ligand

The synthesis of a piano-stool ruthenium hydride, [(η 5 -C 5 Me 5 )Ru(PmIm)H] (PmIm = (N-(1,3,5-trimethylphenyl)-1-(pyrimidin-2-yl)ethan-1-imine) for the dual purpose of catalytic dihydrogen activation and subsequent hydrogen atom transfer for the formation of weak chemical bonds is described. Introduction of a neutral, potentially redox-active PmIm supporting ligand was designed to eliminate the possibility of deleterious C(sp 2 )–H reductive coupling and elimination that has been identified as a deactivation pathway with related rhodium and iridium catalysts. Treatment of [(η 5 -C 5 Me 5 )RuCl 2 ] n with one equivalent PmIm ligand in the presence of zinc and sodium methoxide resulted in isolation of the diruthenium complex, [(η 5 -C 5 Me 5 )Ru(PmIm)] 2 , arising from C–C bond formation between two PmIm chelates. Addition of H 2 to the ruthenium dimer under both thermal and blue light irradiation conditions furnished the targeted hydride, [(η 5 -C 5 Me 5 )Ru(PmIm)H] which has a relatively weak DFT-calculated Ru–H bond dissociation free energy (BDFE) of 47.9 kcal/mol. Addition of TEMPO to [(η 5 -C 5 Me 5 )Ru(PmIm)H] generated the 17-electron metalloradical, [(η 5 -C 5 Me 5 )Ru(PmIm)], which was characterized by EPR spectroscopy. The C–C bond forming process was reversible as irradiation of [(η 5 -C 5 Me 5 )Ru(PmIm)] 2 generated [(η 5 -C 5 Me 5 )Ru(PmIm)H] and a piano-stool ruthenium complex containing an enamide ligand derived from H-atom ab-straction from the PmIm chelate. Equilibration studies were used to establish an experimental estimate of the effective Ru–H BDFE and a value of 50.8 kcal/mol was obtained, in agreement with the observed loss of H 2 and the DFT-computed value. Here, the ruthenium hydride was an effective catalyst for the thermal catalytic hydrogenation of TEMPO, acridine and a cobalt-imido complex and for the selective reduction of azobenzene to diphenylhydrazine using H 2 as the terminal reductant, highlighting the role of this complex is catalytic weak bond formation using H 2 as the stoichiometric reductant.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on NaLiP2(H4O5)2 by Materials Project

Na2Li3P6(HO2)12Na(H2O)6 crystallizes in the trigonal R-3c space group. The structure is three-dimensional and consists of six sodium;hexahydrate molecules and one Na2Li3P6(HO2)12 framework. In the Na2Li3P6(HO2)12 framework, Na1+ is bonded to six O2- atoms to form NaO6 octahedra that share corners with three equivalent LiO4 tetrahedra and corners with three equivalent PO4 tetrahedra. There are three shorter (2.42 Å) and three longer (2.52 Å) Na–O bond lengths. Li1+ is bonded to four O2- atoms to form LiO4 tetrahedra that share corners with two equivalent NaO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 71°. There is two shorter (1.96 Å) and two longer (1.99 Å) Li–O bond length. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one NaO6 octahedra, a cornercorner with one LiO4 tetrahedra, and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 53°. There are a spread of P–O bond distances ranging from 1.50–1.62 Å. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent P5+ atoms. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Na1+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one Li1+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Li1+, and two H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaAl(SO10)2 by Materials Project

NaO6AlO6(SO4)2 is Heusler-like structured and crystallizes in the cubic Pa-3 space group. The structure is zero-dimensional and consists of four sodium;hydroxide;pentahydrate molecules, eight sulfuric acid molecules, and four AlO6 clusters. In each AlO6 cluster, Al is bonded in a distorted octahedral geometry to six equivalent O atoms. All Al–O bond lengths are 1.88 Å. O is bonded in a single-bond geometry to one Al atom.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Visible-light Phase Curves from the Second Year of the TESS Primary Mission

We carried out a systematic study of full-orbit phase curves for known transiting systems in the northern ecliptic sky that were observed during Year 2 of the TESS primary mission. We applied the same methodology for target selection, data processing, and light-curve fitting as we did in our Year 1 study. Out of the 15 transiting systems selected for analysis, seven—HAT-P-7, KELT-1, KELT-9, KELT-16, KELT-20, Kepler-13A, and WASP-12—show statistically significant secondary eclipses and day–night atmospheric brightness modulations. Small eastward dayside hot-spot offsets were measured for KELT-9b and WASP-12b. KELT-1, Kepler-13A, and WASP-12 show additional phase-curve variability attributed to the tidal distortion of the host star; the amplitudes of these signals are consistent with theoretical predictions. We combined occultation measurements from TESS and Spitzer to compute dayside brightness temperatures, TESS-band geometric albedos, Bond albedos, and phase integrals for several systems. The new albedo values solidify the previously reported trend between dayside temperature and geometric albedo for planets with 1500 K < T {sub day} < 3000 K. For Kepler-13Ab, we carried out an atmospheric retrieval of the full secondary eclipse spectrum, which revealed a noninverted temperature–pressure profile, significant H{sub 2}O and K absorption in the near-infrared, evidence for strong optical atmospheric opacity due to sodium, and a confirmation of the high geometric albedo inferred from our simpler analysis. We explore the implications of the phase integrals (ratios of Bond to geometric albedos) for understanding exoplanet clouds. We also report updated transit ephemerides for all of the systems studied in this work.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Characterization of Heparin’s Conformational Ensemble by Molecular Dynamics Simulations and Nuclear Magnetic Resonance Spectroscopy

Heparin is a highly charged, polysulfated polysaccharide and serves as an anticoagulant. Heparin binds to multiple proteins throughout the body, suggesting a large range of potential therapeutic applications. Although its function has been characterized in multiple physiological contexts, heparin’s solution conformational dynamics and structure–function relationships are not fully understood. Molecular dynamics (MD) simulations facilitate the analysis of a molecule’s underlying conformational ensemble, which then provides important information necessary for understanding structure–function relationships. However, for MD simulations to afford meaningful results, they must both provide adequate sampling and accurately represent the energy properties of a molecule. The aim of this study is to compare heparin’s conformational ensemble using two well-developed force fields for carbohydrates, known as GLYCAM06 and CHARMM36, using replica exchange molecular dynamics (REMD) simulations, and to validate these results with NMR experiments. In this work, the anticoagulant sequence, an ultra-low-molecular-weight heparin, known as Arixtra (fondaparinux, sodium), was simulated with both parameter sets. The results suggest that GLYCAM06 matches experimental nuclear magnetic resonance three-bond J-coupling values measured for Arixtra better than CHARMM36. In addition, NOESY and ROESY experiments suggest that Arixtra is very flexible in the sub-millisecond time scale and does not adopt a unique structure at 25 C. Moreover, GLYCAM06 affords a much more dynamic conformational ensemble for Arixtra than CHARMM36.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on NaAuC2 by Materials Project

NaAuC2 crystallizes in the tetragonal P4/mmm space group. The structure is one-dimensional and consists of one sodium molecule and one AuC2 ribbon oriented in the (0, 0, 1) direction. In the AuC2 ribbon, Au1- is bonded in a linear geometry to two equivalent C atoms. Both Au–C bond lengths are 2.00 Å. C is bonded in a distorted linear geometry to one Au1- and one C atom. The C–C bond length is 1.25 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on YH3 by Materials Project

YH3 is Sodium arsenide structured and crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Y3+ is bonded in a 11-coordinate geometry to eleven H1- atoms. There are a spread of Y–H bond distances ranging from 2.12–2.37 Å. There are two inequivalent H1- sites. In the first H1- site, H1- is bonded in a trigonal planar geometry to three equivalent Y3+ atoms. In the second H1- site, H1- is bonded to four equivalent Y3+ atoms to form a mixture of edge, corner, and face-sharing HY4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Solvothermal synthesis and solid-state characterization of metal-metal bonded tetracarboxylatoditechnetium(II,III) polymers

Investigations of solvothermal reactions with pertechnetate, [TcO 4 ] - , have produced four new low-valent Tc extended metal atom chain (EMAC) complexes with multiple metal-metal bonds. The thermal reaction of potassium pertechnetate with glacial acetic acid, under in-situ hydrogen production from the decomposition of sodium borohydride, yields purple elongated crystals determined to be tetraacetato ditechnetium (II,III) acetate (1), [Tc 2 (O 2 CCH 3 ) 4 (μ-O 2 CCH 3 ] n . Compound 1 was characterized by single crystal X-ray diffraction and its magnetic properties recorded between 10 and 300 K. Single crystal X-ray diffraction analysis of 1 indicates the Tc 2 +5 tetraacetato unit is linked by the carboxylate oxygens of the bridging acetate, similar to known chloride and bromide linkage polymers of composition [Tc 2 (μ-O 2 CCH 3 ) 4 Cl] n , and [Tc 2 (μ-O 2 CCH 3 ) 4 Br] n . Here, using the same synthetic method three similar compounds have been synthesized from propionic, benzoic and pivalic acid.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Understanding supercooling mechanism in sodium sulfate decahydrate phase-change material

Salt hydrate-based phase-change materials are considered promising for future heat storage applications in residential heating/cooling systems. Smooth phase transition from the liquid to solid phase and vice versa is essential for effective heat exchanger; however, supercooling in salt hydrates delays the onset of liquid–solid phase transition. We investigate the molecular level mechanism of supercooling in sodium sulfate decahydrate (SSD). SSD is a complex salt hydrate whose properties are governed by electrostatic forces that include pure Coulombic interactions as well as hydrogen bonds. Experimentally, we examine the importance of a nucleator in reducing supercooling temperatures. We investigated the effect of various mass concentrations of a borax nucleator on a decrease of supercooling temperatures. Molecular dynamics simulation techniques are used to obtain a basic understanding of supercooling in SSD. We observe that by introducing borax as a nucleator, there is a decrease in the supercooling temperature before nucleation. Our molecular dynamics simulations show that long-range electrostatics between sodium and sulfate ion pairs and that with polar water molecules is responsible for delayed nucleation in SSD that results in supercooling, and also, dynamics of charged molecules slows down. The lack of crystallization leads to amorphous structures in supercooled SSD.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NpF3 by Materials Project

NpF3 is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Np3+ is bonded in a 5-coordinate geometry to eleven F1- atoms. There are five shorter (2.40 Å) and six longer (2.70 Å) Np–F bond lengths. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a 1-coordinate geometry to four equivalent Np3+ atoms. In the second F1- site, F1- is bonded in a trigonal planar geometry to three equivalent Np3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al3Ir by Materials Project

IrAl3 is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ir is bonded in a 5-coordinate geometry to eleven Al atoms. There are a spread of Ir–Al bond distances ranging from 2.48–2.82 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a trigonal planar geometry to three equivalent Ir and six equivalent Al atoms. All Al–Al bond lengths are 2.82 Å. In the second Al site, Al is bonded in a 1-coordinate geometry to four equivalent Ir and seven Al atoms. There are one shorter (2.66 Å) and three longer (2.77 Å) Al–Al bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PuH3 by Materials Project

PuH3 is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Pu3+ is bonded in a 11-coordinate geometry to eleven H1- atoms. There are a spread of Pu–H bond distances ranging from 2.15–2.39 Å. There are two inequivalent H1- sites. In the first H1- site, H1- is bonded to four equivalent Pu3+ atoms to form a mixture of corner, edge, and face-sharing HPu4 tetrahedra. In the second H1- site, H1- is bonded in a trigonal planar geometry to three equivalent Pu3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on GdH3 by Materials Project

GdH3 is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Gd3+ is bonded in a 11-coordinate geometry to eleven H1- atoms. There are a spread of Gd–H bond distances ranging from 2.15–2.39 Å. There are two inequivalent H1- sites. In the first H1- site, H1- is bonded to four equivalent Gd3+ atoms to form a mixture of corner, edge, and face-sharing HGd4 tetrahedra. In the second H1- site, H1- is bonded in a trigonal planar geometry to three equivalent Gd3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Si3Ir by Materials Project

IrSi3 is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ir4+ is bonded in a 5-coordinate geometry to eleven Si+1.33- atoms. There are a spread of Ir–Si bond distances ranging from 2.49–2.80 Å. There are two inequivalent Si+1.33- sites. In the first Si+1.33- site, Si+1.33- is bonded in a 1-coordinate geometry to four equivalent Ir4+ atoms. In the second Si+1.33- site, Si+1.33- is bonded in a trigonal planar geometry to three equivalent Ir4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CeF3 by Materials Project

CeF3 is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mcm space group. The structure is three-dimensional. Ce3+ is bonded in a 5-coordinate geometry to eleven F1- atoms. There are a spread of Ce–F bond distances ranging from 2.40–2.71 Å. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a trigonal planar geometry to three equivalent Ce3+ atoms. In the second F1- site, F1- is bonded in a trigonal planar geometry to three equivalent Ce3+ atoms. In the third F1- site, F1- is bonded in a 1-coordinate geometry to four equivalent Ce3+ atoms.

36 MATERIALS SCIENCE↗