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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Copper Clusters Containing Hydrides in Trigonal Pyramidal Geometry

Structurally precise copper hydrides [Cu 11 H 2 {S 2 P(O i Pr) 2 } 6 (C≡CR) 3 ], R = Ph (1), C 6 H 4 F (2), and C 6 H 4 OMe (3), were first synthesized from the polyhydrido copper cluster [Cu 20 H 11 {S 2 P(O i Pr) 2 } 9 ] with nine equivalents of terminal alkynes. Later, their isolated yields were significantly improved by direct synthesis from [Cu(CH 3 CN) 4 ](PF 6 ), [NH 4 ][S 2 P(O i Pr) 2 ], NaBH 4 , and alkynes along with NEt 3 in THF. 1, 2, and 3 were fully characterized by single-crystal X-ray diffraction, ESI-MS, and multinuclear NMR spectroscopy. All three clustershave 11 copper atoms, adopting 3,3,4,4,4-pentacapped trigonal prismatic geometry, with two hydrides inside the Cu 11 cage, the position of which was ascertained by a single-crystal neutron diffraction structure of cluster 1 co-crystallized with a [Cu 7 (H){S 2 P(O i Pr) 2 } 6 ] (4) cluster. Six dithiophosphate and three alkynyl ligands stabilize the Cu 11 H 2 core in which the two hydrides adopt a trigonal pyramidal coordination mode. This coordination mode is so far unprecedented for hydride. The 1 H NMR resonance frequency of the two hydrides appears at 4.8 ppm, a value further confirmed by 2 H NMR spectroscopy for their deuteride derivatives [Cu 11 (D) 2 {S 2 P(O i Pr) 2 } 6 (C≡CR) 3 ]. A DFT investigation allows understanding the bonding within this new type of copper(I) hydrides.

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

Is solid copper oxalate a spin chain or a mixture of entangled spin pairs?

Macroscopic assemblies of interacting spins give rise to a broad spectrum of behaviors determined by the spatial arrangement of the magnetic sites and the electronic interactions between them. Compounds of copper (II), in which each copper carries spin 1/2, exhibit a vast variety of physical properties. For antiferromagnetically coupled spin sites, there are two limiting scenarios: spin chains in which the spins can exhibit a long-range order or a mixture of dimers in which the spins within each pair are entangled but do not communicate with the spins from other dimers. In principle, the two types can be distinguished on the basis of experimental observations and modeling using empirically parameterized effective Hamiltonians, but in practice, ambiguity may persist for decades, as is the case for copper oxalate. Here we use high-level ab initio calculations to establish the validity of the nearest-site Heisenberg model and to predict the interaction strength between the magnetic sites. Finally, the computed magnetic susceptibility provides an unambiguous interpretation of magnetic experiments performed throughout half a century, clearly supporting the infinite spin-chain behavior of solid copper oxalate.

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

Electronic Structure and Dynamics of Copper-Doped Indium Phosphide Nanocrystals Studied with Time-Resolved X-ray Absorption and Large-Scale DFT Calculations

Here, the recent development of time-resolved X-ray absorption spectroscopy (TR-XAS) has opened avenues for fundamental research on doped semiconductors. Reported herein are results on the successful doping of indium phosphide nanocrystals (NCs) with copper and subsequent charactenzation with time-resolved X-ray studies and largescale density functional theory (DFT) calculations. The synthetic protocol that was based on the cluster seed method afforded control of both the doping level and the quantity of NCs produced in a batch. The stability of the colloidal dispersion allowed us to monitor the photophysical properties of copper guest ions with static and TR-XAS at the copper K-edge. These data reveal that copper captures a hole from the photoexcited InP NC, and relaxation to the ground state occurs via multiple timescales likely due to the presence of interior and surface-bound dopant ions as well as recombination with surfaceand defect-trapped electrons. Large-scale DFT calculations reveal a striking dependence of the electronic structure on the ligand coating and other effects such as self-compensation.

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

Room-Temperature Dynamics of Vanishing Copper Nanoparticles Supported on Silica

In heterogeneous catalysis, a nanoparticle (NP) system has immediate chemical surroundings with which its interaction needs to be considered, as nanoparticles are typically loaded onto certain supports. Beyond what is known about these interactions, dynamic atomic interactions between the nanoparticle and support could result from the increased energetics at the nanoscale. Here, we show that the dynamic response of atoms in copper nanoparticles to the underlying silica support at room temperature and ambient atmosphere results in the complete disappearance of supported nanoparticles over the course of only a few weeks. A quantitative study of copper nanoparticles at various size regimes (6-17 nm) revealed the significance of size-dependent nanoparticle energetics to the interaction with the support. Extended X-ray absorption fine structure is used to show that copper atoms could readily diffuse into the support to be locally surrounded by oxygen and silicon with structurally disordered outer coordination shells. Increased energetic states at the nanoscale and the energetically favorable configuration of individual copper atoms within silica, identified through EXAFS, are suggested as the cause of nanoparticle disappearance. This unexpected observation opens up new questions as to how nanoparticles interact with surrounding environments that could fundamentally change our conventional view of supported nanoparticle systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Chromatographic and Spectroscopic Study of the Interaction between Polysulfides and Copper Sulfides

To mitigate the “polysulfide shuttle” in lithium–sulfur batteries, different hosting materials that can interact with the polysulfide species physically or chemically have been widely investigated. Copper sulfides as one type of material are believed to have strong chemical interactions with the polysulfide species to consequently influence the performances of Li–S batteries. In this work, high-performance liquid chromatography (HPLC), electrospray ionization mass spectrometry (ESI/MS), scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM-EDS), and inductively coupled plasma optical emission spectroscopy (ICP-OES) were used to systematically investigate the interactions between ether-based polysulfide solutions and copper sulfides (as well as silver sulfide). Furthermore, based on chromatographic and spectroscopic results, the interactions between polysulfides and Cu 2 S can be classified into two types of reactions: one is the redox reaction with the formation of CuS, while another is the complexation reaction with the formation of soluble LiCuS n (n ≥ 4). Contrarily, Ag 2 S (and CuS) shows no interactions with polysulfides. Accordingly, the cycling behaviors of Li–S batteries with copper sulfides as hosting materials or with copper as additives were explained reasonably.

25 ENERGY STORAGE↗
DOE OSTI2015

Enzymatic Mechanism of Copper-Containing Nitrite Reductase

Copper-containing nitrite reductases (CuNiRs) catalyze the reduction of nitrite to nitric oxide, a key step in the denitrification process that maintains balance between organic and inorganic nitrogen. Despite their importance, their functioning is not well understood. In this work, we carry out first-principles calculations and show that the available structural data are consistent only with a single mechanism. For this mechanism, we determine the activation energies, transition states, and minimum energy pathways of CuNiR. The calculations lead to an updated enzymatic mechanism and resolve several controversial issues. In particular, our work identifies the origins of the two protons necessary for the enzymatic function and shows that the transformation from the initial O-coordination of substrate to the final N-coordination of product is achieved by electron transfer from T 1 copper to T 2 copper, rather than by the previously reported side-on coordination of a NO intermediate, which only takes place in the reduced enzyme. Further, we also examine the role of structural change in the critical residue Asp 98 , reported in one experimental study, and find that while the structural change affects the energetics of substrate attachment and product release at the T 2 copper reaction center, it does not significantly affect the activation energy and reaction pathways of the nitrite reduction process.

Anions↗
DOE OSTI2023

Rapid Electron Transfer Self-Exchange in Conformationally Dynamic Copper Coordination Complexes

Here we report the electron transfer (ET) self-exchange rate constants (k 11 ) for a pair of Cu II/I complexes utilizing dpa R (dpa = dipicolylaniline, R = OMe, SMe) ligands assessed by NMR line-broadening experiments. These ligands afford copper complexes that are conformationally dynamic in one oxidation state. With R = OMe, the Cu I complex is dynamic, while with R= SMe, the Cu II complex is dynamic. Both complexes exhibit unexpectedly large k 11 of 2.48(6) x 10 5 and 2.21(9) × 10 6 M –1 s –1 for [CuCl(dpa OMe )] +/0 and [CuCl(dpa SMe )] +/0 , respectively. Among the fastest reported for molecular copper coordination complexes to date, that of [CuCl(dpa SMe )] +/0 exceeds all others by an order of magnitude and compares only to those observed in type 1 blue copper proteins. The dynamicity of these complexes establish pre-steady-state con-formational equilibria that minimize the inner sphere reorganization energies to 0.71 and 0.62 eV for R = OMe and SMe, respectively. In contrast to the emphasis on rigidity in the formulation of entatic states applied to blue copper proteins, the success of these two systems highlight the relevance of conformational dynamicity in mediating rapid ET.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Bioremediation of copper in sediments from a constructed wetland ex situ with the novel bacterium Cupriavidus basilensis SRS

The H-02 constructed wetland was designed to remove metals (primarily copper and zinc) to treat building process water and storm water runoff from multiple sources associated with the Tritium Facility at the DOE-Savannah River Site, Aiken, SC. The concentration of Cu and Zn in the sediments has increased over the lifetime of the wetland and is a concern. A bioremediation option was investigated at the laboratory scale utilizing a newly isolated bacterium of the copper metabolizing genus Cupriavidus isolated from Tim’s Branch Creek, a second-order stream that eventually serves as a tributary to the Savannah River, contaminated with uranium and other metals including copper, nickel, and mercury. Cupriavidus basilensis SRS is a rod-shaped, gram-negative bacterium which has been shown to have predatory tendencies. The isolate displayed resistance to the antibiotics ofloxacin, tetracycline, ciprofloxacin, select fungi, as well as Cu 2+ and Zn 2+ . Subsequent ribosomal sequencing demonstrated a 100% confidence for placement in the genus Cupriavidus and a 99.014% match to the C. basilensis type strain. When H-02 wetland samples were inoculated with Cupriavidus basilensis SRS samples showed significant (p < 0.05) decrease in Cu 2+ concentrations and variability in Zn 2+ concentrations. Over the 72-h incubation there were no significant changes in the inoculate densities (10 6 –10 8 cells/ML) indicating Cupriavidus basilensis SRS resiliency in this environment. This research expands our understanding of the Cupriavidus genus and demonstrates the potential for Cupriavidus basilensis SRS to bioremediate sites impacted with heavy metals, most notably copper.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Cryogenic properties of dispersion strengthened copper for high magnetic fields

Cold deformed copper matrix composite conductors, developed for use in the 100 tesla multi-shot pulsed magnet at the National High Magnetic Field Laboratory (NHMFL), have been characterized. The conductors are alumina strengthened copper which is fabricated by cold drawing that introduces high dislocation densities and high internal stresses. Both alumina particles and high density of dislocations provide us with high tensile strength and fatigue endurance. The conductors also have high electrical conductivities because alumina has limited solubility in Cu and dislocations have little scattering effect on conduction electrons. Such a combination of high strength and high conductivity makes it an excellent candidate over other resistive magnet materials. Thus, characterization is carried out by tensile testing and fully reversible fatigue testing. In tensile tests, the material exceeds the design criteria parameters. In the fatigue tests, both the load and displacement were measured and used to control the amplitude of the tests to simulate the various loading conditions in the pulsed magnet which is operated at 77 K in a non-destructive mode. In order to properly simulate the pulsed magnet operation, strain-controlled tests were more suitable than load controlled tests. For the dispersion strengthened coppers, the strengthening mechanism of the aluminum oxide provided better tensile and fatigue properties over convention copper.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Isentropic expansion of copper plasma in Mbar pressure range at “Luch” laser facility

We present experimental results on thermodynamic properties of dense copper plasma in Mbar pressure range. The laser facility “Luch” with laser intensity 10{sup 14} W/cm{sup 2} is used to compress copper up to ∼8 Mbar by a strong shock wave; subsequent expansion of copper plasma into Al, Ti, Sn allows us to obtain release isentropes of copper by the impedance–matching method. A theoretical analysis and quantum simulations show that in our experiments strongly coupled quantum plasma is generated.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Effect of rapid thermal processing on copper precipitation in p/p{sup +} silicon epitaxial wafers with heavily boron-doped substrates

The effect of rapid thermal processing (RTP) on the formation of copper precipitation in p/p{sup +} silicon (Si) epitaxial wafers was systematically investigated by defect etching and optical microscopy. After RTP preannealing at high temperature (1250 °C/60 s, with cooling rate 30 K/s) followed by the 750 °C/8 h + 1050 °C/16 h low-high (L-H) two-step annealing, it was revealed that the bulk microdefects were found only inside the p{sup +} substrate, manifesting no defects generated in the epitaxial layer. However, it was found that the width of denude zone (DZ) in samples only subjected to L-H two-step annealing was narrower than that of epitaxial layer, which meant that oxygen precipitation was formed in epitaxial layer. It can be concluded that RTP was beneficial to the formation of DZ. Additionally, it was found that the width of DZ has a sharp dependence on the introducing temperature of copper contamination, that is, the corresponding equilibrium concentration of interstitial copper in the Si influence the thermodynamics and kinetics process of the formation of copper precipitation significantly.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Spectral studies of copper(II) complexes of 6-(3-thienyl) pyridine-2-thiosemicarbazone

Two novel copper(II) complexes [Cu(HL)Cl]Cl.H{sub 2}O (1) and [Cu(L)NO{sub 3}]Ðœ‡H{sub 2}O (2) of the three NNS donor thiosemicarbazone ligand 6-(3-thienyl) pyridine-2-thiosemicarbazone have been synthesized. The ligand and its copper(II) complexes were characterized by elemental analysis (C, H, N, and S), FT-IR, UV-visible, magnetic susceptibility and molar conductance. The thiosemicarbazone is present either as the thione form in complex 1 or as thiol form in complex 2 and is coordinated to copper(II) atom via the pyridine nitrogen atom, the azomethine nitrogen atom and the sulfur atom. The physicochemical and spectral data suggest square planar geometry for copper(II) atoms.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Formation kinetics of copper-related light-induced degradation in crystalline silicon

Light-induced degradation (LID) is a deleterious effect in crystalline silicon, which is considered to originate from recombination-active boron-oxygen complexes and/or copper-related defects. Although LID in both cases appears as a fast initial decay followed by a second slower degradation, we show that the time constant of copper-related degradation increases with increasing boron concentration in contrast to boron-oxygen LID. Temperature-dependent analysis reveals that the defect formation is limited by copper diffusion. Finally, interface defect density measurements confirm that copper-related LID is dominated by recombination in the wafer bulk.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Prediction of the critical reduced electric field strength for carbon dioxide and its mixtures with copper vapor from Boltzmann analysis for a gas temperature range of 300 K to 4000 K at 0.4 MPa

The influence of copper vapor mixed in hot CO{sub 2} on dielectric breakdown properties of gas mixture at a fixed pressure of 0.4 MPa for a temperature range of 300 K–4000 K is numerically analyzed. First, the equilibrium composition of hot CO{sub 2} with different copper fractions is calculated using a method based on mass action law. The next stage is devoted to computing the electron energy distribution functions (EEDF) by solving the two-term Boltzmann equation. The reduced ionization coefficient, the reduced attachment coefficient, and the reduced effective ionization coefficient are then obtained based on the EEDF. Finally, the critical reduced electric field (E/N){sub cr} is obtained. The results indicate that an increasing mole fraction of copper markedly reduces (E/N){sub cr} of the CO{sub 2}–Cu gas mixtures because of copper's low ionization potential and large ionization cross section. Additionally, the generation of O{sub 2} from the thermal dissociation of CO{sub 2} contributes to the increase of (E/N){sub cr} of CO{sub 2}–Cu hot gas mixtures from about 2000 K to 3500 K.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Effects of vibration frequency on vibration-assisted nano-scratch process of mono-crystalline copper via molecular dynamics simulation

It has always been a critical issue to understand the material removal behavior of Vibration-Assisted Machining (VAM), especially on atomic level. To find out the effects of vibration frequency on material removal response, a three-dimensional molecular dynamics (MD) model has been established in this research to investigate the effects of scratched groove, crystal defects on the surface quality, comparing with the Von Mises shear strain and tangential force in simulations during nano-scratching process. Comparisons are made among the results of simulations from different vibration frequency with the same scratching feed, depth, amplitude and crystal orientation. Copper potential in this simulation is Embedded-Atom Method (EAM) potential. Interaction between copper and carbon atoms is Morse potential. Simulational results show that higher frequency can make groove smoother. Simulation with high frequency creates more dislocations to improve the machinability of copper specimen. The changing frequency does not have evident effects on Von Mises shear strain. Higher frequency can decrease the tangential force to reduce the consumption of cutting energy and tool wear. In conclusion, higher vibration frequency in VAM on mono-crystalline copper has positive effects on surface finish, machinablility and tool wear reduction.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Non-LTE analysis of neutral copper in late-type metal-poor stars

We investigated the copper abundances of 64 late-type stars in the Galactic disk and halo with effective temperatures from 5400 to 6700 K and [Fe/H] from −1.88 to −0.17. For the first time, the copper abundances are derived using both local thermodynamic equilibrium (LTE) and non-local thermodynamic equilibrium (non-LTE) calculations. High-resolution (R>40,000), high signal-to-noise ratio (S/N>100) spectra from the FOCES spectrograph are used. The atmospheric models are calculated based on the MAFAGS opacity sampling code. All the abundances are derived using spectrum synthesis methods. Our results indicate that the non-LTE effects of copper are important for metal-poor stars, showing a departure of ∼0.17 dex at a metallicity of ∼−1.5. We also find that the copper abundances derived from non-LTE calculations are enhanced compared with those from LTE. The enhancements show clear dependence on the metallicity, which gradually increases with decreasing [Fe/H] for our program stars, leading to a flatter distribution of [Cu/Fe] with [Fe/H] than previous work. There is a hint that the thick- and thin-disk stars have different behaviors in [Cu/Fe], and bending of the disk stars may exist.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Morphology, optical, and adsorption properties of copper-oxide layers deposited from complex compound solutions

A technique for synthesizing gas-sensing copper-oxide layers by layer-by-layer deposition onto glass and plastic substrates is considered. Deposition is based on the oxidation of a copper–ammonia complex by hydrogen peroxide. Layers synthesized at various numbers of deposition cycles are studied by atomicforce microscopy and transmission spectroscopy methods (300–1000 nm). The spectral shape indicates the mixed nature of the oxide with predominant copper oxide (I) Cu{sub 2}O with a corresponding band gap of 2.1 eV. The layers have a continuous granular structure. The surface concentration of Brönsted acid adsorption sites with pK{sub a} ≈ 2.5 (OH acid groups), determined by the indicator method, is 560 μmol/m{sup 2} for the initial films, and threefold increases after heat treatment at 80°C for 30 min. The results obtained are interesting for the use of the described technology for fabricating copper-oxide active layers in gas-sensing sensors operating at room temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2025

The Jupiter Experiments: High-240 Plutonium Metal Plates Separated by Lead and Reflected by Copper

Each layer consisted of a 6 by 6 matrix of either these fuel-filled containers or solid blocks of copper of the same outer dimensions. An example of this arrangement, along with one of the copper inner reflectors, is shown in Figure 1.4. This figure shows the same aluminum containers from Figure 1.3 but with the aluminum containers completely closed. The lifting rings shown on the copper inner reflector were only for assembly and were not present for the measurement (in which the holes were filled with copper plugs). Figure 1.5 shows the loading arrangement of the aluminum containers, along with aluminum shims around the container arrays to ensure a tight fit between these layers and the surrounding reflectors. All plates were in the same orientation; none were rotated in any fashion. Additional loading information for the PAHN plates and plate loading respective to the room entrance are provided in Figures 1.6 and 1.7, respectively.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗