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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Comparison of Measured and Numerically Simulated Turbulence Statistics in a Convective Boundary Layer Over Complex Terrain

High resolution numerical simulation can provide insight into important physical processes that occur within the planetary boundary layer (PBL). The present work employs large eddy simulation (LES) nested within the Weather Forecasting and Research (WRF) framework to simulate real conditions in the convective PBL over an area of complex terrain. A multiple nesting approach has been used to downsize the grid spacing size from 12.15 km (mesoscale) to 0.03 km (LES). To minimize artifacts in theWRF-LES solutions resulting from using an inappropriate grid spacing on the WRF-Meso domain, a careful selection of grid spacing has been conducted. The WRF-LES results have been evaluated with in situ and remote sensing observations collected during the US Department of Energy supported Columbia BasinWind Energy Study (CBWES). The comparison for the first and second order moments, turbulence spectrum, and probability density function (pdf) of wind speed show good agreement between the simulation and data. Furthermore, the WRF-LES variables show a great deal of variability in space and time caused by the complex topography in the LES domain. The WRF-LES results show that the flow structures, such as roll vortices and convective cells, over the domain vary depending on both the spatial location and time of the day. In addition to basic studies related to boundary-layer meteorology, results from these simulations can be used in other applications, such as studying the wind energy resources.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Predicting Deformation Limits of Dual-Phase Steels Under Complex Loading Paths

The deformation limits of various DP980 steels are examined in this study with deformation instability theory. Under uniaxial tension, overall stress-strain curves of the material are estimated based on simple rule of mixture (ROM) with both iso-strain and iso-stress assumptions. Under complex loading paths, actual microstructure-based finite element (FE) method is used to explicitly resolve the deformation incompatibilities between the soft ferrite and hard martensite phases. The results show that, for uniaxial tension, the deformation instability theory with iso-strain-based ROM can be used to provide the lower bound estimate of the uniform elongation (UE) for the various DP980 considered. Under complex loading paths, the deformation instability theory with microstructure-based FE method can be used in examining the effects of various microstructural features on the deformation limits of DP980 steels.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry as a Platform for Characterizing Multimeric Membrane Protein Complexes

Membrane protein characterization is consistently hampered by challenges with expression, purification, and solubilization. Among several biophysical techniques employed for their characterization, native-mass spectrometry (MS) has emerged as a powerful tool for the analysis of membrane proteins and complexes. Here, two MS platforms, the FT-ICR and Q-ToF, have been explored to analyze the homotetrameric water channel protein, AquaporinZ (AqpZ), under non-denaturing conditions. This 97 kDa membrane protein complex can be readily liberated from the octylglucoside (OG) detergent micelle under a range of instrument conditions on both MS platforms. Increasing the applied collision energy of the FT-ICR collision cell yielded varying degrees of tetramer (97 kDa) liberation from the OG micelles, as well as dissociation into the trimeric (72 kDa) and monomeric (24 kDa) substituents. Tandem-MS on the Q-ToF yielded higher intensity tetramer signal and, depending on the m/z region selected, the observed monomer signal varied in intensity. Precursor ion selection of an m/z range above the expected protein signal distribution, followed by mild collisional activation, is able to efficiently liberate AqpZ with a high S/N ratio. The tetrameric charge state distribution obtained on both instruments demonstrated superpositioning of multiple proteoforms due to varying degrees of N-terminal formylation. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Complex collective dynamics of active torque-driven colloids at interfaces

Modern self-assembly techniques aiming to produce complex structural order or functional diversity often rely on non-equilibrium conditions in the system. Light, electric, or magnetic fields are predominantly used to modify interaction profiles of colloidal particles during self-assembly or induce complex out-of-equilibrium dynamic ordering. The energy injection rate, properties of the environment are important control parameters that influence the outcome of active (dynamic) self-assembly. The current review is focused on a case of collective dynamics and self-assembly of particles with externally driven torques coupled to a liquid or solid interface. The complexity of interactions in such systems is further enriched by strong hydrodynamic coupling between particles. Unconventionally ordered dynamic self-assembled patterns, spontaneous symmetry breaking phenomena, self-propulsion, and collective transport have been reported in torque-driven colloids. Some of the features of the complex collective behavior and dynamic pattern formation in those active systems have been successfully captured in simulations.

Snezhko, Alexey↗
DOE OSTI2020

Spectral Element Applications in Complex Nuclear Reactor Geometries: Tet-to-Hex Meshing

The spectral element code Nek5000 is an open-source, higher-order computational fluid dynamics code developed at Argonne National Laboratory. It is designed to solve incompressible Navier-Stokes equations, but it also has a low-Mach-number approximation feature available. Large eddy simulation is approached by explicit filtering of the velocity field (and other fields) to mimic the effect of dissipation due to the unresolved scale. The computational domain is decomposed into second-order hexahedral elements that conform to the boundaries. However, generating a high-quality pure-hexahedral mesh can be challenging for some problems. For simple geometries, traditional blocking methods can be used to decompose the domain into smaller blocks to generate a so-called structural mesh. A structural mesh can maintain good orthogonality but can have a highly skewed mesh to conform to the geometry, as well as unnecessary refinement in the far field. Moreover, for geometries with relative complexity, blocking the geometry becomes impossible. To address these issues, we adopted a let-to-hex strategy to generate a pure hexahedral mesh for Nek5000. First, we generate a pure tetrahedral mesh for the geometry; then we divide one tetrahedral element into four hexahedral elements. A pure tetrahedral mesh could be easily generated for complex geometries by using many current meshing codes. In this paper, we use the commercial codes ANSYS meshing and ANSYSICEM to generate the pure tetrahedral mesh and then convert it to a pure hexahedral mesh. Boundary layers are extruded in ANSYSICEM to maintain near-wall resolution.

ANSYS ICEM↗
DOE OSTI2023

Influence of Rare-Earth Ion Radius on Metal–Metal Charge Transfer in Trinuclear Mixed-Valent Complexes

We report the synthesis and characterization of a highly conjugated bisferrocenyl pyrrolediimine ligand, Fc 2 PyrDIH (1), and its trinuclear complexes with rare earth ions—(Fc 2 PyrDI)M(N(TMS) 2 ) 2 (2-M, M = Sc, Y, Lu, La). Crystal structures, NMR spectra, and UV/Vis-NIR data are presented. The latter are in good agreement with DFT calculations, illuminating the impact of the rare earth ionic radius on NIR charge transfer excitations. For [2-Sc] + , the charge transfer is at 11500 cm -1 , while for [2-Y] + only a d-d transition at 8000 cm -1 is observed. Lu has an ionic radius in between Sc and Y, and the [2-Lu] + complex exhibits both transitions. From TDDFT analysis we assign the 11500 cm -1 transition as a mixture of MLCT and MMCT, rather than pure metal-to-metal CT, because it has significant ligand character. Typically, the ferrocenes have high rotational freedom in bis-ferrocenyl mixed valent complexes. However, in the present (Fc 2 PyrDI)M(N(TMS) 2 ) 2 complexes, ligand-ligand repulsions lock the rotational freedom, so that rare earth ionic radius-dependent geometric differences increasingly influence orbital overlap as the ionic radius falls. The Marcus-Hush coupling constant HAB trends as: [2-Sc] + >[2-Lu] + >[2-Y] +

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Highly Selective Colorimetric and Luminescence Response of a Square-Planar Platinum(II) Terpyridyl Complex to Aqueous TcO 4 –

Molecular recognition of an aqueous pertechnetate (TcO 4 – ) anion is fundamentally challenging partly due to the charge-diffuse nature of this anion, which hampers design of new technologies for its separation and detection. Here, to address this gap, simple salts of transition metal complexes that undergo a distinct spectroscopic change upon exposure to aqueous anions were explored. The Pt(II) complex [Pt(tpy)Br]SbF 6 (tpy = 2,2′;6′,2″-terpyridine) undergoes a dramatic color change and intense luminescence response upon TcO 4 – uptake due to concomitant enhancement of Pt···Pt interactions. The spectroscopic response was highly selective and quantitative for aqueous TcO 4 – among other competing anions. Complementary Raman spectroscopy and microscopy techniques, structural determination, and theoretical methods were employed to elucidate the mechanism of this response at the molecular level.

anions↗
DOE OSTI2016

Influence of Copper Oxidation State on the Bonding and Electronic Structure of Cobalt-Copper Complexes

Heterobimetallic complexes that pair cobalt and copper were synthesized and characterized by a suite of physical methods, including X-ray diffraction, X-ray anomalous scattering, cyclic voltammetry, magnetometry, electronic absorption spectroscopy, electron paramagnetic resonance, and quantum chemical methods. Both Cu(II) and Cu(I) reagents were independently added to a Co(II) metalloligand to provide (py 3 tren)CoCuCl (1-Cl) and (py 3 tren)CoCu(CH 3 CN) (2-CH 3 CN), respectively, where py3tren is the triply deprotonated form of N,N,N-tris(2-(2-pyridylamino)ethyl)amine. Complex 2-CH 3 CN can lose the acetonitrile ligand to generate a coordination polymer consistent with the formula “(py3tren)CoCu” (2). One-electron chemical oxidation of 2-CH 3 CN with AgOTf generated (py 3 tren)CoCuOTf (1-OTf). The Cu(II)/Cu(I) redox couple for 1-OTf and 2-CH 3 CN is reversible at -0.56 and -0.33 V vs Fc + /Fc, respectively. The copper oxidation state impacts the electronic structure of the heterobimetallic core, as well as the nature of the Co–Cu interaction. Quantum chemical calculations showed modest electron delocalization in the (CoCu) +4 state via a Co–Cu σ bond that is weakened by partial population of the Co–Cu σ antibonding orbital. By contrast, no covalent Co–Cu bonding is predicted for the (CoCu) +3 analogue, and the d-electrons are fully localized at individual metals.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Uranyl Carbonate Complexes in Aqueous Solution and Their Ligand NMR Chemical Shifts and 17 O Quadrupolar Relaxation Studied by ab Initio Molecular Dynamics

Dynamic structural effects, NMR ligand chemical shifts, and 17 O NMR quadrupolar relaxation rates are investigated in the series of complexes UO 2 2+ , UO 2 (CO 3 ) 3 4– , and (UO 2 ) 3 (CO 3 ) 6 6– . Car–Parrinello molecular dynamics (CPMD) is used to simulate the dynamics of the complexes in water. NMR properties are computed on clusters extracted from the CPMD trajectories. In the UO 2 2+ complex, coordination at the uranium center by water molecules causes a decrease of around 300 ppm for the uranyl 17 O chemical shift. The final value of this chemical shift is within 40 ppm of the experimental range. The UO 2 (CO 3 ) 3 4– and (UO 2 ) 3 (CO 3 ) 6 6– complexes show a solvent dependence of the terminal carbonate 17 O and 13 C chemical shifts that is less pronounced than that for the uranyl oxygen atom. Corrections to the chemical shift from hybrid functionals and spin–orbit coupling improve the accuracy of chemical shifts if the sensitivity of the uranyl chemical shift to the uranyl bond length (estimated at 140 ppm per 0.1 Å from trajectory data) is taken into consideration. The experimentally reported trend in the two unique 13 C chemical shifts is correctly reproduced for (UO 2 ) 3 (CO 3 ) 6 6– . NMR relaxation rate data support large 17 O peak widths, but remain below those noted in the experimental literature. Furthermore, comparison of relaxation data for solvent-including versus solvent-free models suggest that carbonate ligand motion overshadows explicit solvent effects.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Metal–Ligand Cooperativity Promoting Sulfur Atom Transfer in Ferrous Complexes and Isolation of a Sulfurmethylenephosphorane Adduct

Here, the reaction of elemental sulfur with the cis-divacant octahedral complex [(pyrr 2 py)Fe(OEt 2 )] (1; pyrr 2 py 2– = 3,5- t Bu 2 -bis(pyrrolyl)pyridine) yields the iron dimer [(pyrr-1-S-pyrrpy)Fe] 2 (2; pyrr-1-S-pyrrpy 2– = 3,5-( t Bu2-pyrrolyl)(1-S-3,5-tBu2-pyrrolyl)pyridine) resulting from a pyrr 2 py 2– ligand based S-oxidation of one pyrrole arm. Addition of the phosphorus ylide H 2 CPPh 3 to 1 forms the ylide adduct [(pyrr 2 py)Fe(CH 2 PPh 3 )] (3), which upon reaction with elemental sulfur produces a rare example of a sulfurmethylenephosphorane adduct, [(pyrr 2 py)Fe(SCH 2 PPh 3 )] (4). The sulfur-oxidized pyrrole group of the ligand pyrr-1-S-pyrrpy 2– can be reversed, since complex 2 exhibits S atom transferability via the addition of 2 equiv of H 2 CPPh 3 to yield a mixture of compounds 3 and 4. For all complexes reported, the ferrous ion remains S = 2. Complexes 2–4 were characterized by single-crystal X-ray diffraction as well as 1 H NMR spectroscopy, solid and solution magnetic studies, and 57 Fe Mössbauer spectroscopic measurements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Dynamics of Charged Species in Ionic-Neutral Block Copolymer and Surfactant Complexes [Structural Relaxation and Dynamics of Ionic-Neutral Block Copolymer Surfactant Complexes]

Structure–property relationships of ionic block copolymer (BCP) surfactant complexes are critical toward the progress of favorable engineering design of efficient charge-transport materials. In this paper, molecular dynamics simulations are used to understand the dynamics of charged-neutral BCP and surfactant complexes. The dynamics are examined for two different systems: charged-neutral double-hydrophilic and hydrophobic–hydrophilic block copolymers with oppositely charged surfactant moieties. The dynamics of the surfactant head, tails, and charges are studied for five different BCP volume fractions. We observe that the dynamics of the different species solely depend on the balance between electrostatic and entropic interactions between the charged species and the neutral monomers. The favorable hydrophobic–hydrophobic interactions and the unfavorable hydrophobic–hydrophilic interactions determine the mobilities of the monomers. The dynamical properties of the charge species influence complex formation. Structural relaxations exhibit length-scale dependent behavior, with slower relaxation at the radius of gyration length-scale and faster relaxation at the segmental length-scale, consistent with previous results. The dynamical analysis correlates ion-exchange kinetics to the self-assembly behavior of the complexes.

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

A Neutrally Charged Trimethylmanganese(III) Complex: Synthesis, Characterization, and Disproportionation Chemistry

The synthesis and properties of an unusual, neutrally charged and volatile N,N,N',N'-tetramethylethylenediamine trimethyl manganese(III) complex, (TMEDA)MnMe 3 , are described, along with its facile disproportionation to the corresponding Mn(II) and Mn(IV) complexes. Characterization by single-crystal XRD, UV-vis spectroscopy, high-frequency and -field EPR (HFEPR), magnetic susceptibility, and density functional theory (DFT) computations indicate that the (TMEDA)MnMe3 electronic structure can be described as largely square pyramidal Mn(III) centered. The paucity of manganese(III) polyalkyls and the simplicity and reactivity of this compound implicate it as a potentially useful synthetic building block.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Electroreduction of CO 2 Catalyzed by a Heterogenized Zn–Porphyrin Complex with a Redox-Innocent Metal Center

Transition-metal-based molecular complexes are a class of catalyst materials for electrochemical CO2 reduction to CO that can be rationally designed to deliver high catalytic performance. One common mechanistic feature of these electrocatalysts developed thus far is an electrogenerated reduced metal center associated with catalytic CO2 reduction. Here we report a heterogenized zinc–porphyrin complex (zinc(II) 5,10,15,20-tetramesitylporphyrin) as an electrocatalyst that delivers a turnover frequency as high as 14.4 site–1 s–1 and a Faradaic efficiency as high as 95% for CO2 electroreduction to CO at -1.7 V vs the standard hydrogen electrode in an organic/water mixed electrolyte. While the Zn center is critical to the observed catalysis, in situ and operando X-ray absorption spectroscopic studies reveal that it is redox-innocent throughout the potential range. Cyclic voltammetry indicates that the porphyrin ligand may act as a redox mediator. Chemical reduction of the zinc–porphyrin complex further confirms that the reduction is ligand-based and the reduced species can react with CO2. This represents the first example of a transition-metal complex for CO2 electroreduction catalysis with its metal center being redox-innocent under working conditions.

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

Reaction of Pb(II) and Zn(II) with Ethyl Linoleate To Form Structured Hybrid Inorganic–Organic Complexes: A Model for Degradation in Historic Paint Films

To investigate soap formation in drying oils in historic paints, the reaction between metal acetates (K + , Zn 2+ , Pb 2+ ) and ethyl linoleate (EL) was studied using optical microscopy, X-ray powder diffraction, and electron microscopy. Pb(II) and Zn(II) react rapidly with EL to form highly structured, spherulitic, luminescent crystallites that aggregate. Evidence from Fourier transform infrared (FTIR) and scanning electron microscopy/energy dispersive X-ray analysis and high-resolution synchrotron powder X-ray diffraction indicates that these are organic–inorganic hybrid complexes or coordination polymers. FTIR absorbance peaks at ca. 1540 cm –1 for Pb(II) and ca. 1580 cm –1 for Zn(II) are consistent with the formation of carboxylate complexes. The complexes formed offer insight into the degradation processes observed in oil paint films, suggesting that soap formation is rapid when metal ions are solubilized and can occur with unsaturated fatty acids that are present in fresh oils. These complexes may account for the atypical luminescence observed in lead-containing cured oil paint films.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

C–H Bond Addition across a Transient Uranium–Nitrido Moiety and Formation of a Parent Uranium Imido Complex

Uranium complexes in the + 3 and + 4 oxidation states were prepared using the anionic PN – (PN – = (N-(2-(diisopropylphosphino)-4-methylphenyl)-2,4,6-trimethylanilide) ligand framework. New complexes include the halide starting materials, (PN) 2 U III I (1) and (PN) 2 U IV Cl 2 (2), which both yield (PN) 2 U IV (N 3 ) 2 (3) by reaction with NaN 3 . Compound 3 was reduced with potassium graphite to produce a putative, transient uranium–nitrido moiety that underwent an intramolecular C–H activation to form a rare example of a parent imido complex, [K(THF) 3 ][(PN)U IV (=NH)[ i Pr 2 P(C 6 H 3 Me)N(C 6 H 2 Me 2 CH 2 )]] (4). Here, calculated reaction energy profiles strongly suggest that a C–H insertion becomes unfavorable when a reductant is present, offering a distinctively different reaction pathway than previously observed for other uranium nitride complexes.

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

Spatiotemporal Characteristics and Propagation of Summer Extreme Precipitation Events over United States: A Complex Network Analysis

Complex Network (CN) is a graph-theory based depiction of relation shared by various elements of a complex-dynamical system such as the atmosphere. Here we applied the concept of CN to understand the directionality and topological structure of summer extreme precipitation events (SEPEs) over the conterminous United States (CONUS). The SEPEs are calculated based on the 95th percentile daily rainfall at 0.5ox0.5o spatial resolution for CONUS to investigate the multi-dimensional characteristics of precipitation extremes. The derived CN coefficients (e.g., betweenness centrality, clustering coefficient, orientation, and network divergence) reveal important structural and dynamical information about the topology of the SEPEs and improve understanding of the dominant meteorological patterns. The initiation and propagation of SEPEs from the source-zones to the sink-zones are identified. The SEPEs are influenced by topography, dominant wind patterns, and moisture sources in terms of their topological structure and spatial dynamics.

Mondal, Somnath↗
DOE OSTI2022

MultiSector Dynamics: Advancing the Science of Complex Adaptive Human-Earth Systems

The field of MultiSector Dynamics (MSD) explores the dynamics and co-evolutionary pathways of human and Earth systems with a focus on critical goods, services, and amenities delivered to people through interdependent sectors. This commentary lays out core definitions and concepts, identifies MSD science questions in the context of the current state of knowledge, and describes ongoing activities to expand capacities for open science, leverage revolutions in data and computing, and grow and diversify the MSD workforce. Central to our vision is the ambition of advancing the next generation of complex adaptive human-Earth systems science to better address interconnected risks, increase resilience, and improve sustainability. This will require convergent research and the integration of ideas and methods from multiple disciplines. Understanding the tradeoffs, synergies, and complexities that exist in coupled human-Earth systems is particularly important in the context of energy transitions and increased future shocks.

Reed, Patrick↗