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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Contact ion-pair structure in concentrated cesium chloride aqueous solutions: An extended X-ray absorption fine structure study

The hydration and ion pair structure of Cl- ion in aqueous cesium chloride solutions at 0.5, 6 and 11 mol/kg (H2O) has been studied using Extended X-ray Absorption Fine Structure (EXAFS) at the Cl K-edge. The co-refinement of multiple EXAFS datasets shows the hydration structure of the free Cl- ion is consistent with previously reported studies. In concentrated solution the Cl- ion is strongly associated with the cation forming contact ion pairs with 1.6 and 2.8 Cs ions in 6 and 11 mol/kg aqueous CsCl, respectively. The fact that the degree of ion pairing of Cs-Cl is higher than that of both aqueous RbCl and RbBr at the same concentration is an interesting result as it deviates from the Collins’s law of matching water affinities. The reported Cs-Cl ion-pair structure provides a basis for the development and testing of improved interaction potentials leading to more realistic structures from molecular dynamics (MD) simulations. ACKNOWLEDGEMENT VTP was supported by the Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 103.99-2013.19. Work by JLF was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. The PNC/XSD facilities at the Advanced Photon Source, and research at these facilities, are supported by DOE/BES, the Canadian Light Source and its funding partners, the University of Washington, and the Advanced Photon Source. Use of the Advanced Photon Source, an Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory, was supported by the DOE under Contract No. DE-AC02-06CH11357.

Pham, Van-Thai↗
DOE OSTI2015

A new multi-scale structure finding algorithm to identify cosmological structure

We introduce a new structure finding algorithm that self-consistently parses large scale cosmological structure into clusters, filaments and voids. This structure finding algorithm probes the structure at multiple scales and classifies the appropriate regions with the most probable structure type and size. We show that it can identify the baryon fraction of intercluster medium and cosmological voids.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Structure and thermodynamic stability of UTa 3 O 10 , a U( v )-bearing compound

Heating a mixture of uranyl(VI) nitrate and tantalum(V) oxide in the molar ratio of 2 : 3 to 1400 °C resulted in the formation of a new compound, UTa 3 O 10 . The honey colored to yellow brown crystals of UTa 3 O 10 crystallize in an orthorhombic structure with the space group Fddd (no. 70), lattice parameters a = 7.3947(1), b = 12.7599(2), c = 15.8156(2) Å, and Z = 8. Vertex sharing [TaO 6 ] 7- octahedra of two crystallographically distinct Ta cations form a three dimensional tantalate framework. Within this framework, six membered rings of [TaO 6 ] 7- octahedra are formed within the (001) plane. The center of these rings is occupied by the uranyl cations [UO 2 ] + , with an oxidation state of +5 for uranium. The pentavalence of U and Ta was confirmed by X-ray photoelectron spectroscopy and X-ray adsorption spectroscopy. The enthalpy of formation of UTa 3 O 10 from Ta 2 O 5 , β-U 3 O 7 , and U 3 O 8 has been determined to be 13.1 ± 18.1 kJ mol -1 using high temperature oxide melt solution calorimetry with sodium molybdate as the solvent at 700 °C. The close to zero enthalpy of formation of UTa 3 O 10 can be explained by closely balanced structural stabilizing and destabilizing factors, which may also apply to other UM 3 O 10 compounds.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Can We Describe Graphene Confined Water Structures as Overlapping of Approaching Graphene–Water Interfacial Structures?

We investigate the microscopic mechanisms of the overlap of interfacial structures in confined fluids and attempt to answer the question whether the confined structures can be predicted from the original density profiles of individual solid–fluid interfaces. For that purpose, we perform (globally) isobaric–isothermal (locally, grand canonical) molecular dynamics simulations to extract not only the axial distribution functions of the water sites for the uncoupled graphene–water interfaces, but also those corresponding to the confined aqueous environments over the interplate range $8 ≤ h (Å) ≤ 28$ typically at ambient conditions. We have tested two (i.e., an arithmetic and a geometric) superposition approximations for the singlet density of confined water between flat graphene plates, as well as for a combination of flat and corrugated graphene plates. The outcome of this study suggests that the answer to the title’s question is a “yes”, provided that the interplate distance h is large enough to avoid fluid geometric packing frustration.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗