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Sample records for c-c bond energy

  1. The computation of C-C and N-N bond dissociation energies for singly, doubly, and triply bonded systems

    NASA Technical Reports Server (NTRS)

    Langhoff, Stephen R.; Bauschlicher, Charles W., Jr.; Taylor, Peter R.

    1989-01-01

    The bond dissociation energies (D sub e) of C2H2, C2H4, C2H6, N2, N2H2, and N2H4 are studied at various levels of correlation treatment. The convergence of D sub e with respect to the one particle basis is studied at the single reference modified coupled-pair functional (MCPF) level. At all levels of correlation treatment, the errors in the bond dissociation energies increase with the degree of multiple bond character. The multireference configuration interaction (MRCI) D sub e values, corrected for an estimate of higher excitations, are in excellent agreement with those determined using the size extensive averaged coupled pair functional (ACPF) method. It was found that the full valence complete active space self consistent field (CASSCF)/MRCI calculations are reproduced very well by MRCI calculations based on a CASSCF calculation that includes in the active space only those electrons involved in the C-C or N-N bonds. To achieve chemical accuracy (1 kcal/mole) for the D sub e values of the doubly bonded species C2H4 and N2H2 requires one particle basis sets including up through h angular momentum functions (l = 5) and a multireference treatment of electron correlation: still higher levels of calculation are required to achieve chemical accuracy for the triply bonded species C2H2 and N2.

  2. The computation of C-C and N-N bond dissociation energies for singly, doubly, and triply bonded systems

    NASA Technical Reports Server (NTRS)

    Langhoff, Stephen R.; Bauschlicher, Charles W., Jr.; Taylor, Peter R.

    1991-01-01

    The bond dissociation energies (De) of C2H2, C2H4, C2H6, N2, N2H2, and N2H4 are studied at various levels of correlation treatment. The convergence of De with respect to the one-particle basis is studied at the single-reference modified coupled-pair-functional (MCPF)level. At all levels of correlation treatment, the errors in the bond dissociation energies increase with the degree of multiple bond character. The multireference configuration-interaction (MRCI) De values, corrected for an estimate of higher excitations, are in excellent agreement with those determined using the size-extensive averaged-coupled-pair-functional (ACPF) method. The full-valence complete-active-space self-consistent-field (CASSCF)/MRCI calculations are reproduced very well by MRCI calculations based on a CASSCF calculation that includes in the active space only those electrons involved in the C-C or N-N bonds.

  3. Understanding Rotation about a C=C Double Bond

    ERIC Educational Resources Information Center

    Barrows, Susan E.; Eberlein, Thomas H.

    2005-01-01

    The study focuses on the process and energetic cost of twisting around a C=C double bond and provides instructors with a simple vehicle for rectifying the common misrepresentation of C=C double bonds as rigid and inflexible. Discussions of cis and trans isomers of cycloalkenes are a good entry point for introducing students to the idea of a

  4. Correlation between shape resonance energies and C-C bond length in carbon-containing molecules: Elastic electron scattering and carbon K-shell excitation by photons

    SciTech Connect

    Kimura, Mineo |

    1994-06-01

    We document the correlation of shape resonance energies resulting from (i) elastic electron scattering and (ii) carbon K-shell excitation with ic bond order (C-C bond length) for C{sub 2}H{sub 2}, C{sub 2}H{sub 4}, C{sub 2}H{sub 6}, C{sub 3}H{sub 8}, C{sub 4}H{sub 10}, and C{sub 6}H{sub 6}. A relationship between K-shell {sigma} resonances and bond length was experimentally pointed out previously. These correlations are qualitatively interpreted to indicate that as molecular size increases (or as bond length increases), the configuration space available for valence electrons increases, reducing energy levels rather uniformly and mowing these correlations to emerge. The similarity of shape resonances in electron scattering and photoexcitation occurs because major events in the resonances take place slightly outside the molecular field and receive little influence from the inner structure of the molecule.

  5. Alkali metal mediated CC bond coupling reaction

    SciTech Connect

    Tachikawa, Hiroto

    2015-02-14

    Metal catalyzed carbon-carbon (CC) bond formation is one of the important reactions in pharmacy and in organic chemistry. In the present study, the electron and hole capture dynamics of a lithium-benzene sandwich complex, expressed by Li(Bz){sub 2}, have been investigated by means of direct ab-initio molecular dynamics method. Following the electron capture of Li(Bz){sub 2}, the structure of [Li(Bz){sub 2}]{sup ?} was drastically changed: BzBz parallel form was rapidly fluctuated as a function of time, and a new CC single bond was formed in the C{sub 1}C{sub 1}? position of BzBz interaction system. In the hole capture, the intermolecular vibration between BzBz rings was only enhanced. The mechanism of CC bond formation in the electron capture was discussed on the basis of theoretical results.

  6. Metal-Free Oxidative C?C Bond Formation through C?H Bond Functionalization.

    PubMed

    Narayan, Rishikesh; Matcha, Kiran; Antonchick, Andrey P

    2015-10-12

    The formation of C?C bonds embodies the core of organic chemistry because of its fundamental application in generation of molecular diversity and complexity. C?C bond-forming reactions are well-known challenges. To achieve this goal through direct functionalization of C?H bonds in both of the coupling partners represents the state-of-the-art in organic synthesis. Oxidative C?C bond formation obviates the need for prefunctionalization of both substrates. This Minireview is dedicated to the field of C?C bond-forming reactions through direct C?H bond functionalization under completely metal-free oxidative conditions. Selected important developments in this area have been summarized with representative examples and discussions on their reaction mechanisms. PMID:26239615

  7. Novel C?-C? Bond Cleavages of Tryptophan-Containing Peptide Radical Cations

    NASA Astrophysics Data System (ADS)

    Song, Tao; Hao, Qiang; Law, Chun-Hin; Siu, Chi-Kit; Chu, Ivan K.

    2012-02-01

    In this study, we observed unprecedented cleavages of the C?-C? bonds of tryptophan residue side chains in a series of hydrogen-deficient tryptophan-containing peptide radical cations (M+) during low-energy collision-induced dissociation (CID). We used CID experiments and theoretical density functional theory (DFT) calculations to study the mechanism of this bond cleavage, which forms [M - 116]+ ions. The formation of an ?-carbon radical intermediate at the tryptophan residue for the subsequent C?-C? bond cleavage is analogous to that occurring at leucine residues, producing the same product ions; this hypothesis was supported by the identical product ion spectra of [LGGGH - 43]+ and [WGGGH - 116]+, obtained from the CID of [LGGGH]+ and [WGGGH]+, respectively. Elimination of the neutral 116-Da radical requires inevitable dehydrogenation of the indole nitrogen atom, leaving the radical centered formally on the indole nitrogen atom ([Ind]-2), in agreement with the CID data for [WGGGH]+ and [W1-CH3GGGH]+; replacing the tryptophan residue with a 1-methyltryptophan residue results in a change of the base peak from that arising from a neutral radical loss (116 Da) to that arising from a molecule loss (131 Da), both originating from C?-C? bond cleavage. Hydrogen atom transfer or proton transfer to the ?-carbon atom of the tryptophan residue weakens the C?-C? bond and, therefore, decreases the dissociation energy barrier dramatically.

  8. C-C and C-Heteroatom Bond Dissociation Energies in CH3R?C(OH)2: Energetics for Photocatalytic Processes of Organic Diolates on TiO2 Surfaces

    SciTech Connect

    Wang, Tsang-Hsiu; Dixon, David A.; Henderson, Michael A.

    2010-08-26

    The bond energies of a range of gem-diols, CH3R?C(OH)2 (R? = H, F, Cl, Br, CN, NO2, CF3, CH3CH2, CH3CH2CH2, CH3CH2CH2CH2, ((CH3)2)CH, (CH3)3C, ((CH3)2CH)CH2, (CH3CH2)(CH3)CH, C6H5 (CH3CH2)(CH3)CH) which serve as models for binding to a surface have been studied with density functional theory (DFT) and the molecular orbital G3(MP2) methods to provide thermodynamic data for the analysis of the photochemistry of ketones on TiO2. The ultraviolet (UV) photon-induced photodecomposition of adsorbed acetone and 3,3-dimethylbutanone on the rutile TiO2 (110) surface have been investigated with photon stimulated desorption (PSD) and temperature programmed desorption (TPD). The C-CH3 and C-C(R?) bond dissociation energies in CH3R?C(OH)2 were predicted, and our calculated bond dissociation energies are in excellent agreement with the available experimental values. We used a series of isodemic reactions to provide small corrections to the various bond dissociation energies. The calculated bond dissociation energies are in agreement with the observed photodissociation processes except for R? = CF3, suggesting that these processes are under thermodynamic control. For R? = CF3, reaction dynamics also play a role in determining the photodissociation mechanism. The gas phase Brnsted acidities of the gem-diols were calculated. For three molecules, R? = Cl, Br, and NO2, loss of a proton leads to the formation of a complex of acetic acid with the anion Cl-, Br-, and NO2-. The acidities of these three species are very high with the former two having acidities comparable to CF3SO3H. The ketones (R?RC(=O)) are weak Lewis acids except where addition of OH- leads to the dissociation of the complex to form an anion bonded to acetic acid, R' = NO2, Cl, and Br. The X-C bond dissociation energies for a number of X-CO2- species were calculated and these should be useful in correlating with photochemical reactivity studies.

  9. Synthesis of Biaryls via Benzylic C-C Bond Cleavage of Styrenes and Benzyl Alcohols.

    PubMed

    Kumar, Arvind; Shah, Bhahwal Ali

    2015-11-01

    A metal-free oxidative coupling of styrenes and benzyl alcohols with arenes has been developed for the synthesis of biaryls. The reaction features a conspicuous benzylic C-C bond cleavage of styrenes and benzyl alcohols. The reaction with both substrates proceeds through a common aldehydic intermediate formed through oxidative C-C bond cleavage of alkene and oxidation of benzyl alcohols. The reaction proceeds efficiently over a broad range of substrates with excellent functional group tolerance. PMID:26479321

  10. Structure sensitivity of hydrogenolytic cleavage of endocyclic and exocyclic C-C bonds in methylcyclohexane over supported iridium particles

    SciTech Connect

    Shi, Hui; Gutierrez, Oliver Y.; Haller, Gary L.; Mei, Donghai; Rousseau, Roger J.; Lercher, Johannes A.

    2013-01-02

    Structure sensitivities, H2 pressure effects and temperature dependencies for rates and selectivities of endo- and exocyclic CC bond cleavage in methylcyclohexane were studied over supported Ir catalysts. The rate of endocyclic CC bond cleavage first decreased and then increased with declining Ir dispersion from 0.65 to 0.035. The ring opening (RO) product distribution remained unchanged with varying H2 pressure on small Ir particles, while further shifting to methylhexanes with increasing H2 pressure on large particles. In contrast, the rate and selectivity of exocyclic CC bond cleavage decreased monotonically with increasing H2 pressure and decreasing Ir particle size. The distinct dependencies of endocyclic and exocyclic CC bond cleavage pathways on Ir dispersion and H2 pressure suggest that they are mediated by surface species with different ensemble size requirements. DFT calculations were performed on an Ir50 cluster and an Ir(111) surface, with or without pre-adsorbed hydrogen atoms, to provide insight into the observed effects of particle size and H2 pressure on RO pathways. On small Ir particles, the calculated dehydrogenation enthalpies for all endocyclic bonds were similar and affected to similar extents by H2 pressure; on large particles, the selectivity to n-heptane (via substituted C-C bond cleavage) was even lower than on small particles as a result of the least favorable adsorption and dehydrogenation energetics for hindered bonds. This work was supported by the US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences under Contract DE-AC05-76RL01830. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. The computing time is provided by the user project from EMSL, a national scientific user facility sponsored by the US Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.

  11. Activation of Propane C-H and C-C Bonds by Gas-Phase Pt Atom: A Theoretical Study

    PubMed Central

    Li, Fang-Ming; Yang, Hua-Qing; Ju, Ting-Yong; Li, Xiang-Yuan; Hu, Chang-Wei

    2012-01-01

    The reaction mechanism of the gas-phase Pt atom with C3H8 has been systematically investigated on the singlet and triplet potential energy surfaces at CCSD(T)//BPW91/6-311++G(d, p), Lanl2dz level. Pt atom prefers the attack of primary over secondary C-H bonds in propane. For the Pt + C3H8 reaction, the major and minor reaction channels lead to PtC3H6 + H2 and PtCH2 + C2H6, respectively, whereas the possibility to form products PtC2H4 + CH4 is so small that it can be neglected. The minimal energy reaction pathway for the formation of PtC3H6 + H2, involving one spin inversion, prefers to start at the triplet state and afterward proceed along the singlet state. The optimal C-C bond cleavages are assigned to C-H bond activation as the first step, followed by cleavage of a C-C bond. The C-H insertion intermediates are kinetically favored over the C-C insertion intermediates. From C-C to C-H oxidative insertion, the lowering of activation barrier is mainly caused by the more stabilizing transition state interaction ?E?int, which is the actual interaction energy between the deformed reactants in the transition state. PMID:22942766

  12. Copper-catalyzed aerobic radical CC bond cleavage of NH ketimines

    PubMed Central

    Tnay, Ya Lin; Ang, Gim Yean

    2015-01-01

    Summary We report herein studies on copper-catalyzed aerobic radical CC bond cleavage of NH ketimines. Treatment of NH ketimines having an ?-sp3 hybridized carbon under Cu-catalyzed aerobic reaction conditions resulted in a radical fragmentation with CC bond cleavage to give the corresponding carbonitrile and carbon radical intermediate. This radical process has been applied for the construction of oxaspirocyclohexadienones as well as in the electrophilic cyanation of Grignard reagents with pivalonitrile as a CN source. PMID:26664613

  13. Catalytic C-C bond formation via capture of hydrogenation intermediates.

    PubMed

    Jang, Hye-Young; Krische, Michael J

    2004-09-01

    Although catalytic hydrogenation has been practiced for over a century, use of hydrogen as a terminal reductant in catalytic C-C bond formation has been restricted to processes involving migratory insertion of carbon monoxide, e.g., alkene hydroformylation and related Fischer-Tropsch-type reactions. In an effort to develop hydrogenation as a new method for catalytic cross-coupling, a catalytic system enabling capture of hydrogenation intermediates was recently developed in our lab. These results support the feasibility of developing a broad new family of hydrogen-mediated C-C bond formations. PMID:15379581

  14. Rhodium-Catalyzed Activation and Functionalization of the C-C Bond of Biphenylene

    E-print Network

    Jones, William D.

    Rhodium-Catalyzed Activation and Functionalization of the C-C Bond of Biphenylene Carl N. Iverson August 29, 2001 Biphenylene reacts with the rhodium(I) dimer [(dtbpm)RhCl]2 (1) (dtbpm ) bis have been stoichiometric, although catalytic reactions are known.2 Rhodium complexes in particular have

  15. Conceptual Basis for Understanding C-C Bond Activation in Ethane by Second Row Transition Metal Carbides.

    PubMed

    Sahoo, Sanjubala; Reber, Arthur C; Khanna, Shiv N

    2015-12-24

    It has been suggested that the addition of carbon to Mo and W may improve their catalytic properties and even grant these metal carbides behaviors similar to those of late transition metals such as Pd and Pt. First-principles studies on the C-C bond activation of ethane by 4d transition metal (TM) atoms and TMC molecules have been carried out to develop a conceptual model underlying the changes. We find that the addition of carbon to TM atoms leads to large variations in the activation barrier depending on the metal, and that MoC indeed reveals a pronounced reduction in the C-C bond activation energy. A critical examination of molecular orbitals shows that the changes in reactivity are not linked to a dramatic increase in the filling of 4d states as implied by the analogy with Pd. The reactivity is governed by the location and filling of the 5s and 4d orbitals, with the different orbitals controlling different facets of reactivity. The 5s state controls the initial binding of ethane, with a strong anticorrelation between the ethane binding energy and the 5s occupation, while the location of the 4dz(2) orbital controls the reaction barrier that controls the activation energy for cleaving the C-C bond. PMID:26616749

  16. Formation of CC Bonds via Iridium-Catalyzed Hydrogenation and Transfer Hydrogenation

    PubMed Central

    Bower, John F.; Krische, Michael J.

    2011-01-01

    The formation of CC bonds via catalytic hydrogenation and transfer hydrogenation enables carbonyl and imine addition in the absence of stoichiometric organometallic reagents. In this review, iridium-catalyzed CC bond-forming hydrogenations and transfer hydrogenations are surveyed. These processes encompass selective, atom-economic methods for the vinylation and allylation of carbonyl compounds and imines. Notably, under transfer hydrogenation conditions, alcohol dehydrogenation drives reductive generation of organoiridium nucleophiles, enabling carbonyl addition from the aldehyde or alcohol oxidation level. In the latter case, hydrogen exchange between alcohols and ?-unsaturated reactants generates electrophilenucleophile pairs en route to products of hydro-hydroxyalkylation, representing a direct method for the functionalization of carbinol CH bonds. PMID:21822399

  17. Formation of CC bonds via ruthenium-catalyzed transfer hydrogenation*

    PubMed Central

    Moran, Joseph; Krische, Michael J.

    2013-01-01

    Ruthenium-catalyzed transfer hydrogenation of diverse ?-unsaturated reactants in the presence of aldehydes provides products of carbonyl addition. Dehydrogenation of primary alcohols in the presence of the same ?-unsaturated reactants provides identical products of carbonyl addition. In this way, carbonyl addition is achieved from the alcohol or aldehyde oxidation level in the absence of stoichiometric organometallic reagents or metallic reductants. In this account, the discovery of ruthenium-catalyzed CC bond-forming transfer hydrogenations and the recent development of diastereo- and enantioselective variants are discussed. PMID:23430602

  18. Metalloenzyme-Like Zeolites as Lewis Acid Catalysts for C?C Bond Formation.

    PubMed

    Van de Vyver, Stijn; Romn-Leshkov, Yuriy

    2015-10-19

    The use of metalloenzyme-like zeolites as Lewis acid catalysts for C?C bond formation reactions has received increasing attention over the past few years. In particular, the observation of direct aldol condensation reactions enabled by hydrophobic zeolites with isolated framework metal sites has encouraged the development of catalytic approaches for producing chemicals from biomass-derived compounds. The discovery of new Diels-Alder cycloaddition/dehydration routes and experimental and computational studies of Lewis acid catalyzed carbonyl-ene reactions have given a further boost to this rapidly evolving field. PMID:26465652

  19. Organic chemistry. Rh-catalyzed C-C bond cleavage by transfer hydroformylation.

    PubMed

    Murphy, Stephen K; Park, Jung-Woo; Cruz, Faben A; Dong, Vy M

    2015-01-01

    The dehydroformylation of aldehydes to generate olefins occurs during the biosynthesis of various sterols, including cholesterol in humans. Here, we implement a synthetic version that features the transfer of a formyl group and hydride from an aldehyde substrate to a strained olefin acceptor. A Rhodium (Xantphos)(benzoate) catalyst activates aldehyde carbon-hydrogen (C-H) bonds with high chemoselectivity to trigger carbon-carbon (C-C) bond cleavage and generate olefins at low loadings (0.3 to 2 mole percent) and temperatures (22 to 80C). This mild protocol can be applied to various natural products and was used to achieve a three-step synthesis of (+)-yohimbenone. A study of the mechanism reveals that the benzoate counterion acts as a proton shuttle to enable transfer hydroformylation. PMID:25554782

  20. Rh-Catalyzed CC Bond Cleavage by Transfer Hydroformylation

    PubMed Central

    Murphy, Stephen K.; Park, Jung-Woo; Cruz, Faben A.; Dong, Vy M.

    2015-01-01

    The dehydroformylation of aldehydes to generate olefins occurs during the biosynthesis of various sterols, including cholesterol in humans. Here, we implement a synthetic version that features the transfer of a formyl group and hydride from an aldehyde substrate to a strained olefin acceptor. A Rh(Xantphos)(benzoate) catalyst activates aldehyde CH bonds with high chemoselectivity to trigger CC bond cleavage and generate olefins at low loadings (0.3 to 2 mol%) and temperatures (22 to 80 C). This mild protocol can be applied to various natural products and was used to achieve a three step synthesis of (+)-yohimbenone. A study of the mechanism reveals that the benzoate counterion acts as a proton-shuttle to enable transfer hydroformylation. PMID:25554782

  1. Isomerization around a C N double bond and a C C double bond with a nitrogen atom attached: thermal and photochemical routes

    E-print Network

    Haas, Yehuda

    Isomerization around a C N double bond and a C C double bond with a nitrogen atom attached: thermaltrans isomerization around the double bond in the formaldiminium cation and vinylamine are shown to be possible state, leading to rapid photochemical isomerization following optical excitation. Detailed quantum

  2. Rhodium-Catalyzed C-C Bond Formation via Heteroatom-Directed C-H Bond Activation

    SciTech Connect

    Colby, Denise; Bergman, Robert; Ellman, Jonathan

    2010-05-13

    Once considered the 'holy grail' of organometallic chemistry, synthetically useful reactions employing C-H bond activation have increasingly been developed and applied to natural product and drug synthesis over the past decade. The ubiquity and relative low cost of hydrocarbons makes C-H bond functionalization an attractive alternative to classical C-C bond forming reactions such as cross-coupling, which require organohalides and organometallic reagents. In addition to providing an atom economical alternative to standard cross - coupling strategies, C-H bond functionalization also reduces the production of toxic by-products, thereby contributing to the growing field of reactions with decreased environmental impact. In the area of C-C bond forming reactions that proceed via a C-H activation mechanism, rhodium catalysts stand out for their functional group tolerance and wide range of synthetic utility. Over the course of the last decade, many Rh-catalyzed methods for heteroatom-directed C-H bond functionalization have been reported and will be the focus of this review. Material appearing in the literature prior to 2001 has been reviewed previously and will only be introduced as background when necessary. The synthesis of complex molecules from relatively simple precursors has long been a goal for many organic chemists. The ability to selectively functionalize a molecule with minimal pre-activation can streamline syntheses and expand the opportunities to explore the utility of complex molecules in areas ranging from the pharmaceutical industry to materials science. Indeed, the issue of selectivity is paramount in the development of all C-H bond functionalization methods. Several groups have developed elegant approaches towards achieving selectivity in molecules that possess many sterically and electronically similar C-H bonds. Many of these approaches are discussed in detail in the accompanying articles in this special issue of Chemical Reviews. One approach that has seen widespread success involves the use of a proximal heteroatom that serves as a directing group for the selective functionalization of a specific C-H bond. In a survey of examples of heteroatom-directed Rh catalysis, two mechanistically distinct reaction pathways are revealed. In one case, the heteroatom acts as a chelator to bind the Rh catalyst, facilitating reactivity at a proximal site. In this case, the formation of a five-membered metallacycle provides a favorable driving force in inducing reactivity at the desired location. In the other case, the heteroatom initially coordinates the Rh catalyst and then acts to stabilize the formation of a metal-carbon bond at a proximal site. A true test of the utility of a synthetic method is in its application to the synthesis of natural products or complex molecules. Several groups have demonstrated the applicability of C-H bond functionalization reactions towards complex molecule synthesis. Target-oriented synthesis provides a platform to test the effectiveness of a method in unique chemical and steric environments. In this respect, Rh-catalyzed methods for C-H bond functionalization stand out, with several syntheses being described in the literature that utilize C-H bond functionalization in a key step. These syntheses are highlighted following the discussion of the method they employ.

  3. Ab initio calculations on a novel mode for storing and releasing electrons via C-C bond formation and cleavage

    SciTech Connect

    Cambi, R.; Nottoli, R.; Rosi, M.; Sgamellotti, A. ); Floriani, C. )

    1992-12-23

    Ab initio Hartree-Fock and second-order Moeller-Plesset calculations have been performed on systems which can be viewed as models for [Ni(salophen)] and its reductive product. The results indicate that the metal does not change its oxidation state in the reductive process because no orbitals, localized on nickel and at low energy, are available to accept electrons, except the in-plane d orbital, whose occupation would imply a large increase in the repulsion. The added electrons prefer to form a C-C bond, which can be cleaved restoring the original product. Ni[sup 2+] is electrostatically bonded to the ligand and acts as a shield among the negative charges of the ligand itself. Correlation effects influence the energetic balance of the reductive process but not as heavily as expected for transition metal systems because the electronic distribution at the transition metal ion does not change in the reaction. 17 refs., 2 figs., 2 tabs.

  4. Brnsted-Evans-Polanyi relationships for CC bond forming and CC bond breaking reactions in thiamine-catalyzed decarboxylation of 2-keto acids using density functional theory

    SciTech Connect

    Assary, Rajeev Surendran; Broadbelt, Linda J.; Curtiss, Larry A.

    2011-04-27

    The concept of generalized enzyme reactions suggests that a wide variety of substrates can undergo enzymatic transformations, including those whose biotransformation has not yet been realized. The use of quantum chemistry to evaluate kinetic feasibility is an attractive approach to identify enzymes for the proposed transformation. However, the sheer number of novel transformations that can be generated makes this impractical as a screening approach. Therefore, it is essential to develop structure/activity relationships based on quantities that are more efficient to calculate. In this work, we propose a structure/activity relationship based on the free energy of binding or reaction of non-native substrates to evaluate the catalysis relative to that of native substrates. While Brnsted-Evans-Polanyi (BEP) relationships such as that proposed here have found broad application in heterogeneous catalysis, their extension to enzymatic catalysis is limited. We report here on density functional theory (DFT) studies for CC bond formation and CC bond cleavage associated with the decarboxylation of six 2-keto acids by a thiamine-containing enzyme (EC 1.2.7.1) and demonstrate a linear relationship between the free energy of reaction and the activation barrier. We then applied this relationship to predict the activation barriers of 17 chemically similar novel reactions. These calculations reveal that there is a clear correlation between the free energy of formation of the transition state and the free energy of the reaction, suggesting that this method can be further extended to predict the kinetics of novel reactions through our computational framework for discovery of novel biochemical transformations.

  5. A Homogeneous, Recyclable Polymer Support for Rh(I)-Catalyzed C-C Bond Formation

    PubMed Central

    Jana, Ranjan; Tunge, Jon A.

    2011-01-01

    A robust and practical polymer-supported, homogeneous, recyclable biphephos rhodium(I) catalyst has been developed for C-C bond formation reactions. Control of polymer molecular weight allowed tuning of the polymer solubility such that the polymer-supported catalyst is soluble in nonpolar solvents and insoluble in polar solvents. Using the supported rhodium catalysts, addition of aryl and vinylboronic acids to the electrophiles such as enones, aldehydes, N-sulfonyl aldimines, and alkynes occurs smoothly to provide products in high yields. Additions of terminal alkynes to enones and industrially relevant hydroformylation reactions have also been successfully carried out. Studies show that the leaching of Rh from the polymer support is low and catalyst recycle can be achieved by simple precipitation and filtration. PMID:21895010

  6. Alkynylation of Tertiary Cycloalkanols via Radical C-C Bond Cleavage: A Route to Distal Alkynylated Ketones.

    PubMed

    Wang, Shun; Guo, Li-Na; Wang, Hua; Duan, Xin-Hua

    2015-10-01

    An efficient Na2S2O8-promoted radical coupling of tertiary cycloalkanols with alkynyl hypervalent iodide reagents via C-C bond cleavage was developed. This tandem ring-opening/alkynylation procedure showed some advantages, including mild conditions and wide substrate scope, thus providing a simple synthetic method for ?-, ?- and ?-alkynylated ketones. PMID:26378463

  7. Mechanistic Examination of C?C? Bond Cleavages of Tryptophan Residues during Dissociations of Molecular Peptide Radical Cations

    SciTech Connect

    Song, Tao; Ma, Ching-Yung; Chu, Ivan K.; Siu, Chi-Kit; Laskin, Julia

    2013-02-14

    In this study, we used collision-induced dissociation (CID) to examine the gas-phase fragmentations of [GnW]+ (n = 2-4) and [GXW]+ (X = C, S, L, F, Y, Q) species. The C?C? bond cleavage of a C-terminal decarboxylated tryptophan residue ([M - CO2]+) can generate [M - CO2 - 116]+, [M - CO2 - 117]+, and [1H-indole]+ (m/z 117) species as possible product ions. Competition between the formation of [M - CO2 - 116]+ and [1H-indole]+ systems implies the existence of a proton-bound dimer formed between the indole ring and peptide backbone. Formation of such a proton-bound dimer is facile via a protonation of the tryptophan ?-carbon atom as suggested by density functional theory (DFT) calculations. DFT calculations also suggested the initially formed ion 2--the decarboxylated species that is active against C?C? bond cleavage -can efficiently isomerize to form a more-stable -radical isomer (ion 9) as supported by Rice-Ramsperger-Kassel-Marcus (RRKM) modeling. The C?C? bond cleavage of a tryptophan residue also can occur directly from peptide radical cations containing a basic residue. CID of [WGnR]+ (n = 1-3) radical cations consistently resulted in predominant formation of [M-116]+ product ions. It appears that the basic arginine residue tightly sequesters the proton and allows the charge-remote C?C? bond cleavage to prevail over the charge-directed one. DFT calculations predicted the barrier for the former is 6.2 kcal mol -1 lower than that of the latter. Furthermore, the pathway involving a salt-bridge intermediate also was accessible during such a bond cleavage event.

  8. Gold-Catalyzed Oxidation of Propargylic Ethers with Internal C-C Triple Bonds: Impressive Regioselectivity Enabled by Inductive Effect

    PubMed Central

    Ji, Kegong; DSouza, Brendan; Nelson, Jon; Zhang, Liming

    2014-01-01

    Inductive perturbations of C-C triple bonds are shown to dictate the regiochemistry of gold-catalyzed oxidation of internal C-C triple bonds in the cases of propargylic ethers, resulting in highly regioselective formation of ?-alkoxy-?,?-unsaturated ketones (up to >50/1 selectivity) via ?-oxo gold carbene intermediates. Ethers derived from primary propargylic alcohols can be reliably transformed in good yields, and various functional groups are tolerated. With substrates derived from secondary propargylic alcohols, the development of a new P,N-bidentate ligand enables the minimization of competing alkyl group migration to the gold carbene center over the desired hydride migration; the preferred migration of a phenyl group, however, results in efficient formation of a ?-phenyl-?-alkoxy-?,?-unsaturated ketone. These results further advance the surrogacy of a propargyl moiety to synthetically versatile enone function with reliable and readily predictable regioselectivity. PMID:25284890

  9. Stereoselective total synthesis of (-)-nupharamine utilizing an ?-chlorosulfide and a sulfinimine for C-C bond formation.

    PubMed

    Raghavan, Sadagopan; Rajendar, Sheelamanthula

    2016-01-01

    An efficient stereoselective synthesis of the nuphar alkaloid, (-)-nupharamine, is reported. The key features include the Lewis acid catalyzed reaction of an ?-chlorosulfide with a silyl ketene acetal for C-C bond formation, creation of the stereocenter at C2 by a diastereoselective reaction of allyl indium with a sulfinimine and reductive amination for the introduction of the C6 stereocenter of the piperidine ring. PMID:26490750

  10. Deamination, oxidation, and C-C bond cleavage reactivity of 5-hydroxymethylcytosine, 5-formylcytosine, and 5-carboxycytosine.

    PubMed

    Schiesser, Stefan; Pfaffeneder, Toni; Sadeghian, Keyarash; Hackner, Benjamin; Steigenberger, Barbara; Schrder, Arne S; Steinbacher, Jessica; Kashiwazaki, Gengo; Hfner, Georg; Wanner, Klaus T; Ochsenfeld, Christian; Carell, Thomas

    2013-10-01

    Three new cytosine derived DNA modifications, 5-hydroxymethyl-2'-deoxycytidine (hmdC), 5-formyl-2'-deoxycytidine (fdC) and 5-carboxy-2'-deoxycytidine (cadC) were recently discovered in mammalian DNA, particularly in stem cell DNA. Their function is currently not clear, but it is assumed that in stem cells they might be intermediates of an active demethylation process. This process may involve base excision repair, C-C bond cleaving reactions or deamination of hmdC to 5-hydroxymethyl-2'-deoxyuridine (hmdU). Here we report chemical studies that enlighten the chemical reactivity of the new cytosine nucleobases. We investigated their sensitivity toward oxidation and deamination and we studied the C-C bond cleaving reactivity of hmdC, fdC, and cadC in the absence and presence of thiols as biologically relevant (organo)catalysts. We show that hmdC is in comparison to mdC rapidly oxidized to fdC already in the presence of air. In contrast, deamination reactions were found to occur only to a minor extent. The C-C bond cleavage reactions require the presence of high concentration of thiols and are acid catalyzed. While hmdC dehydroxymethylates very slowly, fdC and especially cadC react considerably faster to dC. Thiols are active site residues in many DNA modifiying enzymes indicating that such enzymes could play a role in an alternative active DNA demethylation mechanism via deformylation of fdC or decarboxylation of cadC. Quantum-chemical calculations support the catalytic influence of a thiol on the C-C bond cleavage. PMID:23980549

  11. Phenyliodonium diacetate mediated direct synthesis of benzonitriles from styrenes through oxidative cleavage of C?C bonds.

    PubMed

    Xu, Jin-Hui; Jiang, Qing; Guo, Can-Cheng

    2013-12-01

    A metal-free PhI(OAc)2 mediated nitrogenation of alkenes through C?C bond cleavage using inorganic ammonia salt as nitrogen source under mild conditions was developed, affording nitriles in moderate to good yields. The advantages of this reaction are mild reaction conditions, operational simplicity, and use of an ammonium salt as nitrogen source. Based upon experimental observations, a plausible reaction mechanism is proposed. PMID:24171555

  12. Unlocking Hydrogenation for C-C Bond Formation: A Brief Overview of Enantioselective Methods

    PubMed Central

    Hassan, Abbas; Krische, Michael J.

    2011-01-01

    Hydrogenation of ?-unsaturated reactants in the presence of carbonyl compounds or imines promotes reductive C-C coupling, providing a byproduct-free alternative to stoichiometric organometallic reagents in an ever-increasing range of C=X (X = O, NR) additions. Under transfer hydrogenation conditions, hydrogen exchange between alcohols and ?-unsaturated reactants triggers generation of electrophile-nucleophile pairs, enabling carbonyl addition directly from the alcohol oxidation level, bypassing discrete alcohol oxidation and generation of stoichiometric byproducts. PMID:22125398

  13. Qualifying Energy Conservation Bonds

    E-print Network

    Briggs, J.

    2013-01-01

    ) of the interest cost associated with the transaction Typical effective interest rates anywhere from 0%-2% depending on credit strength Bond issuance or private placement is acceptable 2 What are QECBs ESL-KT-13-12-39 CATEE 2013: Clean Air Through Energy... Bonds (QECBs) CATEE Conference December 18, 2013 ESL-KT-13-12-39 CATEE 2013: Clean Air Through Energy Efficiency Conference, San Antonio, Texas Dec. 16-18 Originally authorized by the Energy Improvement & Extension Act of 2008 American Recovery...

  14. .c"'''''... '" ~:c c: '"o ':l

    E-print Network

    .c"'''''... '" '".c '-'"c: .c: .D '" ~:c c: '"o ':l '" 0E ':l'" VI 0 '" "'0 '- '" '" "'''' .>c '""-'".c .c .c'"'".ca> V' '" C1' - - - 0 0'" >'0 '" _.w 0 "'0 a>.c W:i:E ' 0 :> '" "VI ~ 3:"" >,c: c: Vl __ 0 -a. .D '"'" VI'" '"' '" '" '" C >, c: '"'- ..., C .c

  15. Matching plasmon resonances to the C=C and C-H bonds in estradiol

    NASA Astrophysics Data System (ADS)

    Mbomson, Ifeoma G.; McMeekin, Scott; De La Rue, Richard; Johnson, Nigel P.

    2015-03-01

    We tune nanoantennas to resonate within mid-infrared wavelengths to match the vibrational resonances of C=C and C-H of the hormone estradiol. Modelling and fabrication of the nanoantennas produce plasmon resonances between 2 ?m to 7 ?m. The hormone estradiol was dissolved in ethanol and evaporated, leaving thickness of a few hundreds of nanometres on top of gold asymmetric split H-like shaped on a fused silica substrate. The reflectance was measured and a red-shift is recorded from the resonators plasmonic peaks. Fourier transform infrared spectroscopy is use to observe enhanced spectra of the stretching modes for the analyte which belongs to alkenyl biochemical group.

  16. Theoretical study of the bond dissociation energies of methanol

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Walch, Stephen P.

    1992-01-01

    A theoretical study of the bond dissociation energies for H2O and CH3OH is presented. The C-H and O-H bond energies are computed accurately with the modified coupled-pair functional method using a large basis set. For these bonds, an accuracy of +/- 2 kcal/mol is achieved, which is consistent with the C-H and C-C single bond energies of other molecules. The C-O bond is much more difficult to compute accurately because it requires higher levels of correlation treatment and more extensive one-particle basis sets.

  17. Cyanoalkylation: Alkylnitriles in Catalytic C?C Bond-Forming Reactions.

    PubMed

    Lpez, Rosa; Palomo, Claudio

    2015-11-01

    Alkylnitriles are one of the most ubiquitous nitrogen-containing chemicals and are widely employed in reactions which result in nitrile-group conversion into other functionalities. Nevertheless, their use as carbon pronucleophiles in carbon-carbon bond-forming reactions has been hampered by difficulties associated mainly with the catalytic generation of active species, that is, ?-cyano carbanions or metalated nitriles. Recent investigations have addressed this challenge and have resulted in different modes of alkylnitrile activation. This review illustrates these findings, which have set the foundation for the development of practical and conceptually new catalytic, direct cyanoalkylation methodologies. PMID:26387483

  18. Short Access to Belt Compounds with Spatially Close C=C Bonds and Their Transannular Reactions.

    PubMed

    Camps, Pelayo; Gmez, Tnia; Otermin, Ane; Font-Bardia, Merc; Estarellas, Carolina; Luque, Francisco Javier

    2015-09-28

    Two domino Diels-Alder adducts were obtained from 3,7-bis(cyclopenta-2,4-dien-1-ylidene)-cis-bicyclo[3.3.0]octane and dimethyl acetylenedicarboxylate or N-methylmaleimide under microwave irradiation. From the first adduct, a C20H24 diene with C2v symmetry was obtained by Zn/AcOH reduction, hydrolysis, oxidative decarboxylation, and selective hydrogenation. Photochemical [2+2] cycloaddition of this diene gave a thermally unstable cyclobutane derivative, which reverts to the diene. However, both the diene and the cyclobutane derivatives could be identified by X-ray diffraction analysis upon irradiation of the diene crystal. New six-membered rings are formed upon the transannular addition of bromine or iodine to the diene. The N-type selectivity of the addition was examined by theoretical calculations, which revealed the distinct susceptibility of the doubly bonded carbon atoms to the bromine attack. PMID:26376331

  19. Bonding and Integration of C-C Composite to Cu-Clad-Molybdenum for Thermal Management Applications

    NASA Technical Reports Server (NTRS)

    Asthana, R.; Singh, M.; Shpargel, T.P.

    2008-01-01

    Two- and three-dimensional carbon-carbon composites with either resin-derived matrix or CVI matrix were joined to Cu-clad-Mo using active Ag-Cu braze alloys for thermal management applications. The joint microstructure and composition were examined using Field-Emission Scanning Electron Microscopy and Energy-Dispersive Spectroscopy, and the joint hardness was characterized using the Knoop microhardness testing. Observations on the infiltration of the composite with molten braze, dissolution of metal substrate, and solute segregation at the C-C surface have been discussed. The thermal response of the integrated assembly is also briefly discussed.

  20. Active Metal Brazing and Adhesive Bonding of Titanium to C/C Composites for Heat Rejection System

    NASA Technical Reports Server (NTRS)

    Singh, M.; Shpargel, Tarah; Cerny, Jennifer

    2006-01-01

    Robust assembly and integration technologies are critically needed for the manufacturing of heat rejection system (HRS) components for current and future space exploration missions. Active metal brazing and adhesive bonding technologies are being assessed for the bonding of titanium to high conductivity Carbon-Carbon composite sub components in various shapes and sizes. Currently a number of different silver and copper based active metal brazes and adhesive compositions are being evaluated. The joint microstructures were examined using optical microscopy, and scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS). Several mechanical tests have been employed to ascertain the effectiveness of different brazing and adhesive approaches in tension and in shear that are both simple and representative of the actual system and relatively straightforward in analysis. The results of these mechanical tests along with the fractographic analysis will be discussed. In addition, advantages, technical issues and concerns in using different bonding approaches will also be presented.

  1. Heterogenised N-heterocyclic carbene complexes: synthesis, characterisation and application for hydroformylation and C-C bond formation reactions.

    PubMed

    Dastgir, Sarim; Coleman, Karl S; Green, Malcolm L H

    2011-01-21

    The imidazolium salts: 1-mesityl-3-(3-trimethoxysilylpropyl)imidazolium iodide and 1-tert-butyl-3-(3-trimethoxysilylpropyl)imidazolium iodide, abbreviated as (tmpMes)HI (3a) and (tmp(t)Bu)HI (3b), respectively, have been synthesised. The palladium(ii) complexes (?(3)-C(3)H(5)) (tmpMes)PdCl (5a) and (?(3)-C(3)H(5))(tmp(t)Bu)PdCl (5b), rhodium(i) and iridium(i) complexes (?(4)-1,5-COD) (tmpMes)MCl, M = Rh (6a), Ir (7a) and (?(4)-1,5-COD)(tmp(t)Bu)MCl, where M = Rh (6b), Ir (7b), were synthesised by silver transmetallation reactions using the silver(i) complexes (tmpMes)AgI (4a) and (tmp(t)Bu)AgI (4b). The iridium complex 7b has been structurally characterised. The Pd(ii) and Rh(i) complexes have been immobilised by attachment to chemically modified MCM-41. The immobilised palladium(ii) materials have been tested as recyclable catalysts for Suzuki type C-C bond formation reactions in water and the immobilised rhodium(i) materials have been examined for their catalytic ability for the hydroformylation of 1-octene. PMID:21116572

  2. Bond dissociation energies and bond orders for some astrophysical molecules

    NASA Astrophysics Data System (ADS)

    Reddy, R. R.; Viswanath, R.

    1989-06-01

    The bond dissociation energies for various astrophysically important diatomic molecules have been determined using a formula in which bond dissociation energies are the sum of the geometric average of the component bond energies and 32.058 times the Pauling electronegativity difference. Bond orders are estimated according to the formula of Reddy et al. (1985, 1987). The results confirm the definition of bond order given by Politzer (1969). The estimated bond energies are found to agree well with previous values and to give an error of 8 percent, as compared to the error of 26.8 percent found using Pauling's (1960) equation.

  3. Gas-phase reaction of CeV2O7+ with C2H4: activation of C-C and C-H bonds.

    PubMed

    Ma, Jia-Bi; Yuan, Zhen; Meng, Jing-Heng; Liu, Qing-Yu; He, Sheng-Gui

    2014-12-15

    The reactivity of metal oxide clusters toward hydrocarbon molecules can be changed, tuned, or controlled by doping. Cerium-doped vanadium cluster cations CeV2O7(+) are generated by laser ablation, mass-selected by a quadrupole mass filter, and then reacted with C2H4 in a linear ion trap reactor. The reaction is characterized by a reflectron time-of-flight mass spectrometer. Three types of reaction channels are observed: 1) single oxygen-atom transfer , 2) double oxygen-atom transfer , and 3) C=C bond cleavage. This study provides the first bimetallic oxide cluster ion, CeV2O7(+), which gives rise to C=C bond cleavage of ethene. Neither Ce(x)O(y)() nor V(x)O(y)() alone possess the necessary topological and electronic properties to bring about such a reaction. PMID:25208512

  4. An asymmetric [3+2] cycloaddition of alkynes with oxiranes by selective C-C bond cleavage of epoxides: highly efficient synthesis of chiral furan derivatives.

    PubMed

    Chen, Weiliang; Fu, Xuan; Lin, Lili; Yuan, Xiao; Luo, Weiwei; Feng, Juhua; Liu, Xiaohua; Feng, Xiaoming

    2014-10-01

    An efficient enantioselective [3+2] cycloaddition of alkynes with oxiranes via selective C-C bond cleavage of epoxides was developed. A number of optically active 2,5-dihydrofurans were obtained in excellent yields (up to 99%) and enantioselectivities (up to 95% ee) under mild reaction conditions. Moreover, chiral tetrahydrofuran could also be obtained by cycloaddition of alkene and oxirane or hydrogenation of chiral 2,5-dihydrofuran. PMID:25133274

  5. NAD(P)H-Independent Asymmetric C=C Bond Reduction Catalyzed by Ene Reductases by Using Artificial Co-substrates as the Hydrogen Donor

    PubMed Central

    Winkler, Christoph K; Clay, Dorina; Entner, Marcello; Plank, Markus; Faber, Kurt

    2014-01-01

    To develop a nicotinamide-independent single flavoenzyme system for the asymmetric bioreduction of C=C bonds, four types of hydrogen donor, encompassing more than 50 candidates, were investigated. Six highly potent, cheap, and commercially available co-substrates were identified that (under the optimized conditions) resulted in conversions and enantioselectivities comparable with, or even superior to, those obtained with traditional two-enzyme nicotinamide adenine dinucleotide phosphate (NAD(P)H)-recycling systems. PMID:24382795

  6. C-H vs C-C Bond Activation of Acetonitrile and Benzonitrile via Oxidative Addition: Rhodium vs Nickel and Cp* vs Tp

    E-print Network

    Jones, William D.

    C-H vs C-C Bond Activation of Acetonitrile and Benzonitrile via Oxidative Addition: Rhodium vs@chem.rochester.edu Abstract: The photochemical reaction of (C5Me5)Rh(PMe3)H2 (1) in neat acetonitrile leads to formation of the C-H activation product, (C5Me5)Rh(PMe3)(CH2CN)H (2). Thermolysis of this product in acetonitrile

  7. Measurements of electron attachment lineshapes and cross sections at ultra-low electron energies for CF2Cl2, c-C4F6, c-C4F8 and c-C7F14

    NASA Technical Reports Server (NTRS)

    Chutjian, A.; Alajajian, S. H.

    1987-01-01

    Electron-attachment cross sections are reported in the electron energy range 0-160 meV, and at energy resolutions of 7.0 and 7.5 meV (FWHM), for the molecules CF2Cl2 (dichlorodifluoromethane), c-C4F6 (perfluorocyclobutene), c-C4F8 (perfluorocyclobutane), and c-C7F14 (perfluoromethylcyclohexane). Use is made of the Kr photoionization method. Measured attachment lineshapes are deconvoluted from the spectral slit function, and are converted to cross sections by normalization through thermal attachment-rate constants. Comparisons are made with attachment cross sections derived from several independent sets of swarm-measured rate constants, and with collisional ionization (high-Rydberg attachment) data.

  8. Design and Synthesis of Chiral Zn2+ Complexes Mimicking Natural Aldolases for Catalytic CC Bond Forming Reactions in Aqueous Solution

    PubMed Central

    Itoh, Susumu; Sonoike, Shotaro; Kitamura, Masanori; Aoki, Shin

    2014-01-01

    Extending carbon frameworks via a series of CC bond forming reactions is essential for the synthesis of natural products, pharmaceutically active compounds, active agrochemical ingredients, and a variety of functional materials. The application of stereoselective CC bond forming reactions to the one-pot synthesis of biorelevant compounds is now emerging as a challenging and powerful strategy for improving the efficiency of a chemical reaction, in which some of the reactants are subjected to successive chemical reactions in just one reactor. However, organic reactions are generally conducted in organic solvents, as many organic molecules, reagents, and intermediates are not stable or soluble in water. In contrast, enzymatic reactions in living systems proceed in aqueous solvents, as most of enzymes generally function only within a narrow range of temperature and pH and are not so stable in less polar organic environments, which makes it difficult to conduct chemoenzymatic reactions in organic solvents. In this review, we describe the design and synthesis of chiral metal complexes with Zn2+ ions as a catalytic factor that mimic aldolases in stereoselective CC bond forming reactions, especially for enantioselective aldol reactions. Their application to chemoenzymatic reactions in aqueous solution is also presented. PMID:24481060

  9. Intramolecular C-C Bond Coupling of Nitriles to a Diimine Ligand in Group 7 Metal Tricarbonyl Complexes.

    PubMed

    Yempally, Veeranna; Fan, Wai Yip; Arndtsen, Bruce A; Bengali, Ashfaq A

    2015-12-01

    Dissolution of M(CO)3(Br)(L(Ar)) [L(Ar) = (2,6-Cl2-C6H3-NCMe)2CH2] in either acetonitrile [M = Mn, Re] or benzonitrile (M = Re) results in C-C coupling of the nitrile to the diimine ligand. When reacted with acetonitrile, the intermediate adduct [M(CO)3(NCCH3)(L(Ar))]Br forms and undergoes an intramolecular C-C coupling reaction between the nitrile carbon and the methylene carbon of the ?-diimine ligand. PMID:26554575

  10. Chlorine atom-initiated low-temperature oxidation of prenol and isoprenol: The effect of C=C double bonds on the peroxy radical chemistry in alcohol oxidation

    DOE PAGESBeta

    Welz, Oliver; Savee, John D.; Osborn, David L.; Taatjes, Craig A.

    2014-07-04

    The chlorine atom-initiated oxidation of two unsaturated primary C5 alcohols, prenol (3-methyl-2-buten-1-ol, (CH3)2CCHCH2OH) and isoprenol (3-methyl-3-buten-1-ol, CH2C(CH3)CH2CH2OH), is studied at 550 K and low pressure (8 Torr). The time- and isomer-resolved formation of products is probed with multiplexed photoionization mass spectrometry (MPIMS) using tunable vacuum ultraviolet ionizing synchrotron radiation. The peroxy radical chemistry of the unsaturated alcohols appears much less rich than that of saturated C4 and C5 alcohols. The main products observed are the corresponding unsaturated aldehydes prenal (3-methyl-2-butenal) from prenol oxidation and isoprenal (3-methyl-3-butenal) from isoprenol oxidation. No significant products arising from QOOH chemistry are observed. Thesemoreresults can be qualitatively explained by the formation of resonance stabilized allylic radicals via H-abstraction in the Cl + prenol and Cl + isoprenol initiation reactions. The loss of resonance stabilization upon O2 addition causes the energies of the intermediate wells, saddle points, and products to increase relative to the energy of the initial radicals and O2. These energetic shifts make most product channels observed in the peroxy radical chemistry of saturated alcohols inaccessible for these unsaturated alcohols. The experimental findings are underpinned by quantum-chemical calculations for stationary points on the potential energy surfaces for the reactions of the initial radicals with O2. Under our conditions, the dominant channels in prenol and isoprenol oxidation are the chain-terminating HO2-forming channels arising from radicals, in which the unpaired electron and the OH group are on the same carbon atom, with stable prenal and isoprenal co-products, respectively. These results suggest that the presence of C=C double bonds in alcohols will reduce low-temperature reactivity during autoignition.less

  11. A metal-free tandem C-C/C-O bond formation approach to densely functionalized indolyl 4H-chromenes catalyzed by polystyrene-supported p-toluenesulfonic acid under solvent-free conditions.

    PubMed

    Shinde, Vijay Vilas; Jeong, Yong Seok; Jeong, Yeon Tae

    2015-05-01

    A new environmentally benign and highly convergent protocol for the synthesis of indolyl 4H-chromene derivatives has been developed. This one-pot three-component condensation reaction of salicylaldehyde, cyclic 1,3-diketones, and indole is promoted by PS-PTSA as a reusable heterogeneous acid catalyst under solvent-free conditions. This protocol demonstrates several notable advantages such as that the catalyst is readily available and can be recovered and reused for at least five runs without any significant impact on product yields, high atom economy, excellent yields, and efficiency of producing three new bonds (two C-C and one C-O) and one stereo center in a single operation. PMID:25802172

  12. Chemistry of Materials 1989, 1,83-101 How C-C Bonds Are Formed and How They Influence

    E-print Network

    Li, Jing

    , or A, where R designates by convention a rare-earth metal, T, a transition metal, and Table I. C metallic, whereas the alkaline-earth metal carbide CaCz, a structure belonging to the same crystal family-C Distances in Some Selected Binary and Ternary Metal Carbides cryst struct c-c, A ref A, an alkaline-earth

  13. Three methods to measure RH bond energies

    SciTech Connect

    Berkowitz, J.; Ellison, G.B.; Gutman, D.

    1993-03-21

    In this paper the authors compare and contrast three powerful methods for experimentally measuring bond energies in polyatomic molecules. The methods are: radical kinetics; gas phase acidity cycles; and photoionization mass spectroscopy. The knowledge of the values of bond energies are a basic piece of information to a chemist. Chemical reactions involve the making and breaking of chemical bonds. It has been shown that comparable bonds in polyatomic molecules, compared to the same bonds in radicals, can be significantly different. These bond energies can be measured in terms of bond dissociation energies.

  14. Templated C-C and C-N Bond Formation Facilitated by a Molybdenum(VI) Metal Center.

    PubMed

    Zwettler, Niklas; Dup, Antoine; Schachner, Jrg A; Belaj, Ferdinand; Msch-Zanetti, Nadia C

    2015-12-21

    Preparation of molybdenum dioxido complexes with novel iminophenolate ligands bearing pendant secondary amide functionalities led to unprecedented C-C and C-N coupling reactions of two ?-iminoamides upon coordination. The diastereoselective cyclization to asymmetric imidazolidines occurs at the metal center in two consecutive steps via a monocoupled intermediate. A meaningful mechanism is proposed on the basis of full characterization of intermediate and final molybdenum-containing products by spectroscopic means and by single-crystal X-ray diffraction analyses. This process constitutes the first example of a diastereoselective self-cyclization of two ?-iminoamides. PMID:26646158

  15. Push-Pull Buta-1,2,3-trienes: exceptionally low rotational barriers of cumulenic C=C bonds and proacetylenic reactivity.

    PubMed

    Gawel, Przemyslaw; Wu, Yi-Lin; Finke, Aaron D; Trapp, Nils; Zalibera, Michal; Boudon, Corinne; Gisselbrecht, Jean-Paul; Schweizer, W Bernd; Gescheidt, Georg; Diederich, Franois

    2015-04-13

    A variety of asymmetrically donor-acceptor-substituted [3]cumulenes (buta-1,2,3-trienes) were synthesized by developed procedures. The activation barriers to rotation ?G(?) were measured by variable temperature NMR spectroscopy and found to be as low as 11.8?kcal?mol(-1) , in the range of the barriers for rotation around sterically hindered single bonds. The central C=C bond of the push-pull-substituted [3]cumulene moiety is shortened down to 1.22? as measured by X-ray crystallography, leading to a substantial bond length alternation (BLA) of up to 0.17?. All the experimental results are supported by DFT calculations. Zwitterionic transition states (TS) of bond rotation confirm the postulated proacetylenic character of donor-acceptor [3]cumulenes. Additional support for the proacetylenic character of these chromophores is provided by their reaction with tetracyanoethene (TCNE) in a cycloaddition-retroelectrocyclization (CA-RE) cascade characteristic of donor-polarized acetylenes. PMID:25765373

  16. Accurate In Bond Energies

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Arnold, James O. (Technical Monitor)

    1999-01-01

    InXn atomization energies are computed for n = 1-3 and X = H, Cl, and CH3. The geometries and frequencies are determined using density functional theory. The atomization energies are computed at the coupled cluster level of theory. The complete basis set limit is obtained by extrapolation. The scalar relativistic effect is computed using the Douglas-Kroll approach. While the heats of formation for InH, InCl and InCl3 are in good agreement with experiment, the current results show that the experimental value for In(CH3)3 must be wrong.

  17. Chlorine atom-initiated low-temperature oxidation of prenol and isoprenol: The effect of C=C double bonds on the peroxy radical chemistry in alcohol oxidation

    SciTech Connect

    Welz, Oliver; Savee, John D.; Osborn, David L.; Taatjes, Craig A.

    2014-07-04

    The chlorine atom-initiated oxidation of two unsaturated primary C5 alcohols, prenol (3-methyl-2-buten-1-ol, (CH3)2CCHCH2OH) and isoprenol (3-methyl-3-buten-1-ol, CH2C(CH3)CH2CH2OH), is studied at 550 K and low pressure (8 Torr). The time- and isomer-resolved formation of products is probed with multiplexed photoionization mass spectrometry (MPIMS) using tunable vacuum ultraviolet ionizing synchrotron radiation. The peroxy radical chemistry of the unsaturated alcohols appears much less rich than that of saturated C4 and C5 alcohols. The main products observed are the corresponding unsaturated aldehydes prenal (3-methyl-2-butenal) from prenol oxidation and isoprenal (3-methyl-3-butenal) from isoprenol oxidation. No significant products arising from QOOH chemistry are observed. These results can be qualitatively explained by the formation of resonance stabilized allylic radicals via H-abstraction in the Cl + prenol and Cl + isoprenol initiation reactions. The loss of resonance stabilization upon O2 addition causes the energies of the intermediate wells, saddle points, and products to increase relative to the energy of the initial radicals and O2. These energetic shifts make most product channels observed in the peroxy radical chemistry of saturated alcohols inaccessible for these unsaturated alcohols. The experimental findings are underpinned by quantum-chemical calculations for stationary points on the potential energy surfaces for the reactions of the initial radicals with O2. Under our conditions, the dominant channels in prenol and isoprenol oxidation are the chain-terminating HO2-forming channels arising from radicals, in which the unpaired electron and the OH group are on the same carbon atom, with stable prenal and isoprenal co-products, respectively. These results suggest that the presence of C=C double bonds in alcohols will reduce low-temperature reactivity during autoignition.

  18. Heme Carbonyls: Environmental Effects on ?CO and FeC/CO Bond Length Correlations

    PubMed Central

    Silvernail, Nathan J.; Roth, Arne; Noll, Bruce C.; Scheidt, W. Robert; Schulz, Charles E.

    2006-01-01

    The synthesis and characterization of four low-spin (carbonyl)iron(II) tetraphenylporphyrinates, [Fe(TPP)(CO)(L)], where L = 1-methylimidazole, 2-methylimidazole, 1,2-dimethylimidazole (unsolvated) and 1,2-dimethylimidazole (toluene solvate) are reported. The complexes show nearly the same value of ?CO in toluene solution (196972 cm?1) but a large range of CO stretching frequencies in the solid-state (19261968 cm?1). The large solid-state variation results from CO interactions in the solid-state as shown by an examination of the crystal structures of the four complexes. The high precision of the four structures obtained allows us to make a number of structural and spectroscopic correlations that describe the FeCO and NImFeCO units. The values of ?CO and the FeC and CO bond distances are strongly correlated and provide a structural as well as a spectroscopic correlation of the ? back-bonding model. The interactions of CO described are closely related to the large range of CO stretching frequencies observed in heme proteins and specific interactions observed in carbonylmyoglobin (MbCO). PMID:16218637

  19. DMSO/I2 mediated C-C bond cleavage of ?-ketoaldehydes followed by C-O bond formation: a metal-free approach for one-pot esterification.

    PubMed

    Venkateswarlu, Vunnam; Aravinda Kumar, K A; Gupta, Sorav; Singh, Deepika; Vishwakarma, Ram A; Sawant, Sanghapal D

    2015-08-01

    A novel and efficient I2/DMSO mediated metal-free strategy is presented for the direct C-C bond cleavage of aryl-/heteroaryl- or aliphatic ?-ketoaldehydes by C2-decarbonylation and C1-carbonyl oxidation to give the corresponding carboxylic acids followed by esterification in one pot, offering excellent yields in both the steps. Here, DMSO acts as the oxygen source/oxidant and this reaction works very well under both conventional heating and microwave irradiation. This is a very simple and convenient protocol. PMID:26110656

  20. How and Why Does Ni(0) Promote Smooth Etheric C?O Bond Cleavage and C?C Bond Formation? A Theoretical Study.

    PubMed

    Ogawa, Hiroyuki; Minami, Hiroki; Ozaki, Takashi; Komagawa, Shinsuke; Wang, Chao; Uchiyama, Masanobu

    2015-09-28

    Ni-catalyzed cross-coupling between aryl alkyl ethers (ArOR) and Grignard reagents (RMgBr), known since 1979, proceeds under mild conditions in many cases. Although the reaction routes of various synthetic protocols involving transition-metal-catalyzed C?O bond activation have been elucidated, the mechanism of this etheric Kumada-Tamao-Curriu reaction remains enigmatic. This is because oxidative addition of inert etheric C?O to Ni(0) is thermodynamically and kinetically unfavorable, making it hard to explain the observed high reactivity of ether toward Ni catalysts. In this work, we used DFT calculations to identify a plausible reaction pathway by the Ni(0) -ate complex, which enables smooth C?O bond cleavage and R-group transfer with reasonable activation barriers; this mechanism also accounts for the ineffectiveness of Pd catalysts. These results throw new light on both C?O activation and cross-coupling, and should be valuable for further rational development of the methodologies. PMID:26294322

  1. Bond Dissociation Energies of Organic Molecules

    E-print Network

    Ellison, Barney

    . Introduction The making and breaking of bonds is the basis of all chemical transformation. A sound knowledge to understanding chemical processes.1 The energy required for homolytic bond cleavage at 298 K corresponds of chemical reactions for which experimental bond en- thalpies are available. One must be cautious, however

  2. Bioinspired Nonheme Iron Catalysts for C-H and C?C Bond Oxidation: Insights into the Nature of the Metal-Based Oxidants.

    PubMed

    Oloo, Williamson N; Que, Lawrence

    2015-09-15

    Recent efforts to design synthetic iron catalysts for the selective and efficient oxidation of C-H and C?C bonds have been inspired by a versatile family of nonheme iron oxygenases. These bioinspired nonheme (N4)Fe(II) catalysts use H2O2 to oxidize substrates with high regio- and stereoselectivity, unlike in Fenton chemistry where highly reactive but unselective hydroxyl radicals are produced. In this Account, we highlight our efforts to shed light on the nature of metastable peroxo intermediates, which we have trapped at -40 C, in the reactions of the iron catalyst with H2O2 under various conditions and the high-valent species derived therefrom. Under the reaction conditions that originally led to the discovery of this family of catalysts, we have characterized spectroscopically an Fe(III)-OOH intermediate (EPR gmax = 2.19) that leads to the hydroxylation of substrate C-H bonds or the epoxidation and cis-dihydroxylation of C?C bonds. Surprisingly, these organic products show incorporation of (18)O from H2(18)O, thereby excluding the possibility of a direct attack of the Fe(III)-OOH intermediate on the substrate. Instead, a water-assisted mechanism is implicated in which water binding to the iron(III) center at a site adjacent to the hydroperoxo ligand promotes heterolytic cleavage of the O-O bond to generate an Fe(V)(O)(OH) oxidant. This mechanism is supported by recent kinetic studies showing that the Fe(III)-OOH intermediate undergoes exponential decay at a rate enhanced by the addition of water and retarded by replacement of H2O with D2O, as well as mass spectral evidence for the Fe(V)(O)(OH) species obtained by the Costas group. The nature of the peroxo intermediate changes significantly when the reactions are carried out in the presence of carboxylic acids. Under these conditions, spectroscopic studies support the formation of a (?(2)-acylperoxo)iron(III) species (EPR gmax = 2.58) that decays at -40 C in the absence of substrate to form an oxoiron(IV) byproduct, along with a carboxyl radical that readily loses CO2. The alkyl radical thus formed either reacts with O2 to form benzaldehyde (as in the case of PhCH2COOH) or rebounds with the incipient Fe(IV)(O) moiety to form phenol (as in the case of C6F5COOH). Substrate addition leads to its 2-e(-) oxidation and inhibits these side reactions. The emerging mechanistic picture, supported by DFT calculations of Wang and Shaik, describes a rather flat reaction landscape in which the (?(2)-acylperoxo)iron(III) intermediate undergoes O-O bond homolysis reversibly to form an Fe(IV)(O)(()OC(O)R) species that decays to Fe(IV)(O) and RCO2() or isomerizes to its Fe(V)(O)(O2CR) electromer, which effects substrate oxidation. Another short-lived S = 1/2 species just discovered by Talsi that has much less g-anisotropy (EPR gmax = 2.07) may represent either of these postulated high-valent intermediates. PMID:26280131

  3. Reversible Sigma C-C Bond Formation Between Phenanthroline Ligands Activated by (C5Me5)2Yb

    SciTech Connect

    Nocton, Gré gory; Lukens, Wayne W.; Booth, Corwin H.; Rozenel, Sergio S.; Medling, Scott A.; Maron, Laurent; Andersen, Richard A.

    2014-06-26

    The electronic structure and associated magnetic properties of the 1,10-phenanthroline adducts of Cp*2Yb are dramatically different from those of the 2,2?-bipyridine adducts. The monomeric phenanthroline adducts are ground state triplets that are based upon trivalent Yb(III), f13, and (phen ) that are only weakly exchange coupled, which is in contrast to the bipyridine adducts whose ground states are multiconfigurational, open-shell singlets in which ytterbium is intermediate valent ( J. Am. Chem. Soc 2009, 131, 6480; J. Am. Chem. Soc 2010, 132, 17537). The origin of these different physical properties is traced to the number and symmetry of the LUMO and LUMO+1 of the heterocyclic diimine ligands. The bipy has only one 1 orbital of b1 symmetry of accessible energy, but phen has two orbitals of b1 and a2 symmetry that are energetically accessible. The carbon p-orbitals have different nodal properties and coefficients and their energies, and therefore their populations change depending on the position and number of methyl substitutions on the ring. A chemical ramification of the change in electronic structure is that Cp 2Yb(phen) is a dimer when crystallized from toluene solution, but a monomer when sublimed at 180190 C. When 3,8-Me2phenanthroline is used, the adduct Cp*2Yb(3,8-Me2phen) exists in the solution in a dimer monomer equilibrium in which G is near zero. The adducts with 3-Me, 4-Me, 5-Me, 3,8-Me2, and 5,6-Me2-phenanthroline are isolated and characterized by solid state X-ray crystallography, magnetic susceptibility and LIII-edge XANES spectroscopy as a function of temperature and variable-temperature 1H NMR spectroscopy.

  4. Reversible sigma C-C bond formation between phenanthroline ligands activated by (C5Me5)2Yb.

    PubMed

    Nocton, Grgory; Lukens, Wayne W; Booth, Corwin H; Rozenel, Sergio S; Medling, Scott A; Maron, Laurent; Andersen, Richard A

    2014-06-18

    The electronic structure and associated magnetic properties of the 1,10-phenanthroline adducts of Cp*2Yb are dramatically different from those of the 2,2'-bipyridine adducts. The monomeric phenanthroline adducts are ground state triplets that are based upon trivalent Yb(III), f(13), and (phen(-) ) that are only weakly exchange coupled, which is in contrast to the bipyridine adducts whose ground states are multiconfigurational, open-shell singlets in which ytterbium is intermediate valent ( J. Am. Chem. Soc 2009 , 131 , 6480 ; J. Am. Chem. Soc 2010 , 132 , 17537 ). The origin of these different physical properties is traced to the number and symmetry of the LUMO and LUMO+1 of the heterocyclic diimine ligands. The bipy(-) has only one ?*1 orbital of b1 symmetry of accessible energy, but phen(-) has two ?* orbitals of b1 and a2 symmetry that are energetically accessible. The carbon p?-orbitals have different nodal properties and coefficients and their energies, and therefore their populations change depending on the position and number of methyl substitutions on the ring. A chemical ramification of the change in electronic structure is that Cp*2Yb(phen) is a dimer when crystallized from toluene solution, but a monomer when sublimed at 180-190 C. When 3,8-Me2phenanthroline is used, the adduct Cp*2Yb(3,8-Me2phen) exists in the solution in a dimer-monomer equilibrium in which ?G is near zero. The adducts with 3-Me, 4-Me, 5-Me, 3,8-Me2, and 5,6-Me2-phenanthroline are isolated and characterized by solid state X-ray crystallography, magnetic susceptibility and LIII-edge XANES spectroscopy as a function of temperature and variable-temperature (1)H NMR spectroscopy. PMID:24852897

  5. Acetaldehyde partial oxidation on the Au(111) model catalyst surface: C-C bond activation and formation of methyl acetate as an oxidative coupling product

    NASA Astrophysics Data System (ADS)

    Karatok, Mustafa; Vovk, Evgeny I.; Shah, Asad A.; Turksoy, Abdurrahman; Ozensoy, Emrah

    2015-11-01

    Partial oxidation of acetaldehyde (CH3CHO) on the oxygen pre-covered Au(111) single crystal model catalyst was investigated via Temperature Programmed Desorption (TPD) and Temperature Programmed Reaction Spectroscopy (TPRS) techniques, where ozone (O3) was utilized as the oxygen delivery agent providing atomic oxygen to the reacting surface. We show that for low exposures of O3 and small surface oxygen coverages, two partial oxidation products namely, methyl acetate (CH3COOCH3) and acetic acid (CH3COOH) can be generated without the formation of significant quantities of carbon dioxide. The formation of methyl acetate as the oxidative coupling reaction product implies that oxygen pre-covered Au(111) single crystal model catalyst surface can activate C-C bonds. In addition to the generation of these products; indications of the polymerization of acetaldehyde on the gold surface were also observed as an additional reaction route competing with the partial and total oxidation pathways. The interplay between the partial oxidation, total oxidation and polymerization pathways reveals the complex catalytic chemistry associated with the interaction between the acetaldehyde and atomic oxygen on catalytic gold surfaces.

  6. Iron-catalyzed aerobic oxidative cleavage of the C-C ?-bond using air as the oxidant: chemoselective synthesis of carbon chain-shortened aldehydes, ketones and 1,2-dicarbonyl compounds.

    PubMed

    Xing, Qi; Lv, Hui; Xia, Chungu; Li, Fuwei

    2016-01-11

    A simple iron-catalyzed aerobic oxidative C-C ?-bond cleavage of ketones has been developed. Readily available and environmentally benign air is used as the oxidant. This reaction avoids the use of noble metal catalysts or specialized oxidants, chemoselectively yielding carbon chain-shortened aldehydes, ketones and 1,2-dicarbonyl compounds without overoxidation. PMID:26529597

  7. Three methods to measure RH bond energies

    SciTech Connect

    Berkowitz, J. ); Ellison, G.B. ); Gutman, D. )

    1994-03-17

    We present a critical review of three different experimental methods used to measure bond energies: radical kinetics, gas-phase acidity cycles, and photoionization mass spectrometry. These experimental techniques are currently in use to measure the bond energies of a large number of molecules. We discuss the basic premises of each of these experiments and explicitly try to point out the strengths and weaknesses of each method. We directly compare each of these procedures using a set of about 30 important molecules. These three different techniques have only a few disagreements among them, the case of ethylene being the most serious. For the overwhelming number of studies, all measurements lead to bond energies within each other's error bars. We include tables of ionization potentials, electron affinities, and heats of formation for about 40 important organic and inorganic radicals. We also list bond energies for the parent molecules at 0 and 298 K. 273 refs., 10 figs., 5 tabs.

  8. Theoretical study of the bond dissociation energies of propyne (C3H4)

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.

    1992-01-01

    The C-C and C-H bond dissociation energies (BDEs) of propyne have been computed using the modified coupled-pair functional method. Due to hyperconjugation, the C-C and methyl C-H single bonds are stronger and weaker, respectively than those in ethane. The acetylenic C-H and C triple bond C BDEs are larger and smaller, respectively, than in acetylene, also as a result of the hyperconjugation. Our best estimate of 92.5 +/- 2 kcal/mol for the methyl C-H BDE in propyne is slightly larger than the experimental value. For the acetylenic C-H BDE in propyne we predict 135.9 +/- 2 kcal/mol.

  9. Chlorination-Promoted Skeletal-Cage Transformations of C88 Fullerene by C2 Losses and a C?C Bond Rotation.

    PubMed

    Yang, Shangfeng; Wei, Tao; Scheurell, Kerstin; Kemnitz, Erhard; Troyanov, Sergey I

    2015-10-19

    High-temperature chlorination of fullerene C88 (isomer 33) with VCl4 gives rise to skeletal transformations affording several nonclassical (NC) fullerene chlorides, C86 (NC1)Cl24/26 and C84 (NC2)Cl26 , with one and two heptagons, respectively, in the carbon cages. The branched skeletal transformation including C2 losses as well as a Stone-Wales rearrangement has been comprehensively characterized by the structure determination of two intermediates and three final chlorination products. Quantum-chemical calculations demonstrate that the average energy of the C?Cl bond is significantly increased in chlorides of nonclassical fullerenes with a large number of chlorinated sites of pentagon-pentagon adjacency. PMID:26332709

  10. Adhesive bonding using variable frequency microwave energy

    DOEpatents

    Lauf, R.J.; McMillan, A.D.; Paulauskas, F.L.; Fathi, Z.; Wei, J.

    1998-09-08

    Methods of facilitating the adhesive bonding of various components with variable frequency microwave energy are disclosed. The time required to cure a polymeric adhesive is decreased by placing components to be bonded via the adhesive in a microwave heating apparatus having a multimode cavity and irradiated with microwaves of varying frequencies. Methods of uniformly heating various articles having conductive fibers disposed therein are provided. Microwave energy may be selectively oriented to enter an edge portion of an article having conductive fibers therein. An edge portion of an article having conductive fibers therein may be selectively shielded from microwave energy. 26 figs.

  11. Adhesive bonding using variable frequency microwave energy

    DOEpatents

    Lauf, R.J.; McMillan, A.D.; Paulauskas, F.L.; Fathi, Z.; Wei, J.

    1998-08-25

    Methods of facilitating the adhesive bonding of various components with variable frequency microwave energy are disclosed. The time required to cure a polymeric adhesive is decreased by placing components to be bonded via the adhesive in a microwave heating apparatus having a multimode cavity and irradiated with microwaves of varying frequencies. Methods of uniformly heating various articles having conductive fibers disposed therein are provided. Microwave energy may be selectively oriented to enter an edge portion of an article having conductive fibers therein. An edge portion of an article having conductive fibers therein may be selectively shielded from microwave energy. 26 figs.

  12. Adhesive bonding using variable frequency microwave energy

    DOEpatents

    Lauf, Robert J. (Oak Ridge, TN); McMillan, April D. (Knoxville, TN); Paulauskas, Felix L. (Oak Ridge, TN); Fathi, Zakaryae (Cary, NC); Wei, Jianghua (Raleigh, NC)

    1998-01-01

    Methods of facilitating the adhesive bonding of various components with variable frequency microwave energy are disclosed. The time required to cure a polymeric adhesive is decreased by placing components to be bonded via the adhesive in a microwave heating apparatus having a multimode cavity and irradiated with microwaves of varying frequencies. Methods of uniformly heating various articles having conductive fibers disposed therein are provided. Microwave energy may be selectively oriented to enter an edge portion of an article having conductive fibers therein. An edge portion of an article having conductive fibers therein may be selectively shielded from microwave energy.

  13. Interaction of a pseudo-? C-C bond with cuprous and argentous chlorides: Cyclopropane?CuCl and cyclopropane?AgCl investigated by rotational spectroscopy and ab initio calculations.

    PubMed

    Zaleski, Daniel P; Mullaney, John C; Bittner, Dror M; Tew, David P; Walker, Nicholas R; Legon, Anthony C

    2015-10-28

    Strongly bound complexes (CH2)3?MCl (M = Cu or Ag), formed by non-covalent interaction of cyclopropane and either cuprous chloride or argentous chloride, have been generated in the gas phase by means of the laser ablation of either copper or silver metal in the presence of supersonically expanded pulses of a gas mixture containing small amounts of cyclopropane and carbon tetrachloride in a large excess of argon. The rotational spectra of the complexes so formed were detected with a chirped-pulse, Fourier transform microwave spectrometer and analysed to give rotational constants and Cu and Cl nuclear quadrupole coupling constants for eight isotopologues of each of (CH2)3?CuCl and (CH2)3?AgCl. The geometry of each of these complexes was established unambiguously to have C2v symmetry, with the three C atoms coplanar, and with the MCl molecule lying along a median of the cyclopropane C3 triangle. This median coincides with the principal inertia axis a in each of the two complexes (CH2)3?MCl. The M atom interacts with the pseudo-? bond linking the pair of equivalent carbon atoms (F)C (F = front) nearest to it, so that M forms a non-covalent bond to one C-C edge of the cyclopropane molecule. The (CH2)3?MCl complexes have similar angular geometries to those of the hydrogen- and halogen-bonded analogues (CH2)3?HCl and (CH2)3?ClF, respectively. Quantitative details of the geometries were determined by interpretation of the observed rotational constants and gave results in good agreement with those from ab initio calculations carried out at the CCSD(T)(F12*)/aug-cc-pVTZ-F12 level of theory. Interesting geometrical features are the lengthening of the (F)C-(F)C bond and the shrinkage of the two equivalent (B)C-(F)C (B = back) bonds relative to the C-C bond in cyclopropane itself. The expansions of the (F)C-(F)C bond are 0.1024(9) and 0.0727(17) in (CH2)3?CuCl and (CH2)3?AgCl, respectively, according to the determined r0 geometries. The C-C bond lengthening is in each case about four times that observed by similar methods in the corresponding complexes of MCl with ethyne and ethene, even though the cyclopropane complexes are more weakly bound than their ethyne and ethene analogues. Reasons for the larger increase in r(CC) in the pseudo-? complexes are discussed. PMID:26520520

  14. Interaction of a pseudo-? CC bond with cuprous and argentous chlorides: Cyclopropane⋯CuCl and cyclopropane⋯AgCl investigated by rotational spectroscopy and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Zaleski, Daniel P.; Mullaney, John C.; Bittner, Dror M.; Tew, David P.; Walker, Nicholas R.; Legon, Anthony C.

    2015-10-01

    Strongly bound complexes (CH2)3⋯MCl (M = Cu or Ag), formed by non-covalent interaction of cyclopropane and either cuprous chloride or argentous chloride, have been generated in the gas phase by means of the laser ablation of either copper or silver metal in the presence of supersonically expanded pulses of a gas mixture containing small amounts of cyclopropane and carbon tetrachloride in a large excess of argon. The rotational spectra of the complexes so formed were detected with a chirped-pulse, Fourier transform microwave spectrometer and analysed to give rotational constants and Cu and Cl nuclear quadrupole coupling constants for eight isotopologues of each of (CH2)3⋯CuCl and (CH2)3⋯AgCl. The geometry of each of these complexes was established unambiguously to have C2v symmetry, with the three C atoms coplanar, and with the MCl molecule lying along a median of the cyclopropane C3 triangle. This median coincides with the principal inertia axis a in each of the two complexes (CH2)3⋯MCl. The M atom interacts with the pseudo-? bond linking the pair of equivalent carbon atoms FC (F = front) nearest to it, so that M forms a non-covalent bond to one CC edge of the cyclopropane molecule. The (CH2)3⋯MCl complexes have similar angular geometries to those of the hydrogen- and halogen-bonded analogues (CH2)3⋯HCl and (CH2)3⋯ClF, respectively. Quantitative details of the geometries were determined by interpretation of the observed rotational constants and gave results in good agreement with those from ab initio calculations carried out at the CCSD(T)(F12*)/aug-cc-pVTZ-F12 level of theory. Interesting geometrical features are the lengthening of the FCFC bond and the shrinkage of the two equivalent BCFC (B = back) bonds relative to the CC bond in cyclopropane itself. The expansions of the FCFC bond are 0.1024(9) and 0.0727(17) in (CH2)3⋯CuCl and (CH2)3⋯AgCl, respectively, according to the determined r0 geometries. The CC bond lengthening is in each case about four times that observed by similar methods in the corresponding complexes of MCl with ethyne and ethene, even though the cyclopropane complexes are more weakly bound than their ethyne and ethene analogues. Reasons for the larger increase in r(CC) in the pseudo-? complexes are discussed.

  15. Direct, Redox Neutral Prenylation and Geranylation of Secondary Carbinol C-H Bonds: C4 Regioselectivity in Ruthenium Catalyzed C-C Couplings of Dienes to ?-Hydroxy Esters

    PubMed Central

    Leung, Joyce C.; Geary, Laina M.; Chen, Te-Yu; Zbieg, Jason R.

    2012-01-01

    The ruthenium catalyst generated in situ from Ru3(CO)12 and tricyclohexylphosphine, PCy3, promotes the redox-neutral C-C coupling of aryl substituted ?-hydroxy esters to isoprene and myrcene at the diene C4-position, resulting in direct carbinol C-H prenylation and geranylation, respectively. This process enables direct conversion of secondary to tertiary alcohols in the absence of stoichiometric byproducts or premetallated reagents, and is the first example of C4-regioselectivity in catalytic C-C couplings of 2-substituted dienes to carbonyl partners. Mechanistic studies corroborate a catalytic cycle involving diene-carbonyl oxidative coupling. PMID:22985393

  16. Chords: Em 022000 Em Em Em Em C C C C

    E-print Network

    Reiners, Peter W.

    Verse 1 Chorus Verse 2 Chorus Verse 3 Chords: Em 022000 C 035553 G 320002 F 133211 Intro: Em Em Em Em C C C C Em Em Em Em C C C C Em Em Em Em C C C C Em Em Em Em C C C C Verse: Em Em Em Em C C C C G G G G G G G G Em Em Em Em C C C C G G G G G G G G Em Em Em Em C C C C G G G G G G G G Em Em Em Em C C

  17. Measurements of electron attachment lineshapes and cross sections at ultralow electron energies for c-C6F10, c-C6F12, C8F16 and 1,1,2-C2Cl3F3

    NASA Technical Reports Server (NTRS)

    Alajajian, S. H.; Chutjian, A.

    1986-01-01

    Electron attachment cross sections are reported in the electron energy range 0-160 meV and at energy resolutions of 4.5-7.5 meV (FWHM) for the molecules c-C6F10 (perfluorocyclohexene), c-C6F12 (perfluoro-1,2-dimethylcyclobutane), C8F16 (perfluoro-1,3-dimethylcyclohexane) and 1,1,2-C2Cl3F3 (1,1,2-trichlorotrifluoroethane). Use is made of the Kr photoionization technique, and measured attachment lineshapes are converted to cross sections by normalization through attachment rate constants. Comparisons are made with attachment cross sections derived from swarm-measured rate constants. Similar to previous results in eight other molecules, the present four molecules exhibit resolution-limited onsets at a threshold consistent with an s-wave attachment behavior and with a neutral-negative-ion curve crossing at zero energy.

  18. Bond-Energy and Surface-Energy Calculations in Metals

    ERIC Educational Resources Information Center

    Eberhart, James G.; Horner, Steve

    2010-01-01

    A simple technique appropriate for introductory materials science courses is outlined for the calculation of bond energies in metals from lattice energies. The approach is applied to body-centered cubic (bcc), face-centered cubic (fcc), and hexagonal-closest-packed (hcp) metals. The strength of these bonds is tabulated for a variety metals and is

  19. Aliphatic C-C Bond Cleavage of ?-Hydroxy Ketones by Non-Heme Iron(II) Complexes: Mechanistic Insight into the Reaction Catalyzed by 2,4'-Dihydroxyacetophenone Dioxygenase.

    PubMed

    Rahaman, Rubina; Paria, Sayantan; Paine, Tapan Kanti

    2015-11-16

    2,4'-Dihydroxyacetophenone dioxygenase (DAD) is a bacterial non-heme enzyme that carries out oxygenative aliphatic C-C bond cleavage of 2,4'-dihydroxyacetophenone (an ?-hydroxy ketone) with the incorporation of both the oxygen atoms of dioxygen into the cleavage products. The crystal structure of the iron enzyme DAD has recently been determined, but very little is known about the mechanism of the C-C bond cleavage reaction. With the objective of gaining insights into the mechanism of the reaction catalyzed by DAD, six new biomimetic iron(II)-?-hydroxy ketone complexes, [(Tp(Ph2))Fe(II)(PHAP)] (1), [(Tp(Ph2))Fe(II)(HCH)] (2), [(Tp(Ph2))Fe(II)(HBME)] (3), [(Tp(Ph2))Fe(II)(CHPE)] (4), [(6-Me3-TPA)Fe(II)(PHAP)](+) (5), and [(6-Me3-TPA)Fe(II)(HCH)](+) (6) (Tp(Ph2) = hydrotris(3,5-diphenylpyrazol-1-yl)borate, 6-Me3-TPA = tris(6-methyl-2-pyridylmethyl)amine, PHAP-H = 2-phenyl-2-hydroxyacetophenone, HCH-H = 2-hydroxycyclohexanone, HBME-H = 2-hydroxy-1,2-bis(4-methoxyphenyl)ethanone, and CHPE-H = 1-(4-chlorophenyl)-2-hydroxy-2-phenylethanone), have been isolated and characterized. The single-crystal X-ray structure of 2 shows a five-coordinate iron(II) complex with one tridentate facial ligand and a monoanionic bidentate ?-hydroxy ketone, resulting in a distorted-square-pyramidal coordination geometry at the iron center. The iron(II) complexes react with dioxygen to oxidatively cleave the aliphatic C-C bonds of the coordinated ?-hydroxy ketones to afford 2 equiv of carboxylic acids. Mechanistic studies reveal that the C-C bond cleavage reaction proceeds through an intradiol pathway. Additionally, the coordinated ?-hydroxy ketones in all of the complexes, except in complex 4, undergo two-electron oxidation to form the corresponding 1,2-diketones. However, the yields of 1,2-diketones are higher with the iron complexes of the tripodal N4 ligand (6-Me3-TPA) in comparison to the facial N3 ligand (Tp(Ph2)). These results strongly support the natural selection of a facial N3 environment at the active site of the iron enzyme DAD. PMID:26536067

  20. Ruthenium(0) Catalyzed Endiyne-?-Ketol [4 + 2] Cycloaddition: Convergent Assembly of Type II Polyketide Substructures via C-C Bond Forming Transfer Hydrogenation.

    PubMed

    Saxena, Aakarsh; Perez, Felix; Krische, Michael J

    2015-05-13

    Upon exposure of 3,4-benzannulated 1,5-diynes (benzo-endiynes) to ?-ketols (?-hydroxyketones) in the presence of Ru(0) catalysts derived from Ru3(CO)12 and RuPhos or CyJohnPhos, successive redox-triggered C-C coupling occurs to generate products of [4 + 2] cycloaddition. The proposed catalytic mechanism involves consecutive alkyne-carbonyl oxidative couplings to form transient oxaruthanacycles that suffer ?-ketol mediated transfer hydrogenolysis. This process provides a new, convergent means of assembling Type II polyketide substructures. PMID:25938947

  1. Interaction geometries and energies of hydrogen bonds to C[double bond]O and C[double bond]S acceptors: a comparative study.

    PubMed

    Wood, Peter A; Pidcock, Elna; Allen, Frank H

    2008-08-01

    The occurrence, geometries and energies of hydrogen bonds from N-H and O-H donors to the S acceptors of thiourea derivatives, thioamides and thiones are compared with data for their O analogues - ureas, amides and ketones. Geometrical data derived from the Cambridge Structural Database indicate that hydrogen bonds to the C[double bond]S acceptors are much weaker than those to their C[double bond]O counterparts: van der Waals normalized hydrogen bonds to O are shorter than those to S by approximately 0.25 A. Further, the directionality of the approach of the hydrogen bond with respect to S, defined by the C[double bond]S...H angle, is in the range 102-109 degrees , much lower than the analogous C[double bond]O...H angle which lies in the range 127-140 degrees . Ab initio calculations using intermolecular perturbation theory show good agreement with the experimental results: the differences in hydrogen-bond directionality are closely reproduced, and the interaction energies of hydrogen bonds to S are consistently weaker than those to O, by approximately 12 kJ mol(-1), for each of the three compound classes. There are no CSD examples of hydrogen bonds to aliphatic thiones, (Csp(3))(2)C=S, consistent with the near-equality of the electronegativities of C and S. Thioureas and thioamides have electron-rich N substituents replacing the Csp(3) atoms. Electron delocalization involving C[double bond]S and the N lone pairs then induces a significant >C(delta+)[double bond]S(delta-) dipole, which enables the formation of the medium-strength C[double bond]S...H bonds observed in thioureas and thioamides. PMID:18641451

  2. Rhodium(III)-Catalyzed Directed ortho-C-H Bond Functionalization of Aromatic Ketazines via C-S and C-C Coupling.

    PubMed

    Wen, Jing; Wu, An; Wang, Mingyang; Zhu, Jin

    2015-11-01

    Described herein is a convenient and efficient method for sulfuration and olefination of aromatic ketazines via rhodium-catalyzed oxidative C-H bond activation. A range of substituted substrates are supported, and a possible mechanism is proposed according to experimental results of kinetic isotopic effect, reversibility studies, and catalysis of rhodacycle intermediate c1. PMID:26417874

  3. All-carbon quaternary stereogenic centers in acyclic systems through the creation of several C-C bonds per chemical step.

    PubMed

    Marek, Ilan; Minko, Yury; Pasco, Morgane; Mejuch, Tom; Gilboa, Noga; Chechik, Helena; Das, Jaya P

    2014-02-19

    In the past few decades, it has become clear that asymmetric catalysis is one of the most powerful methods for the construction of carbon-carbon as well as carbon-heteroatom bonds in a stereoselective manner. However, when structural complexity increases (i.e., all-carbon quaternary stereogenic center), the difficulty in reaching the desired adducts through asymmetric catalytic reactions leads to a single carbon-carbon bond-forming event per chemical step between two components. Issues of efficiency and convergence should therefore be addressed to avoid extraneous chemical steps. In this Perspective, we present approaches that tackle the stimulating problem of efficiency while answering interesting synthetic challenges. Ideally, if one could create all-carbon quaternary stereogenic centers via the creation of several new carbon-carbon bonds in an acyclic system and in a single-pot operation from simple precursors, it would certainly open new horizons toward solving the synthetic problems. Even more important for any further design, the presence of polyreactive intermediates in synthesis (bismetalated, carbenoid, and oxenoids species) becomes now an indispensable tool, as it creates consecutively the same number of carbon-carbon bonds as in a multi-step process, but in a single-pot operation. PMID:24512113

  4. The Bond Dissociation Energies of 1-Butene

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R. (Technical Monitor)

    1994-01-01

    The bond dissociation energies of 1-butene and several calibration systems are computed using the G2(MP2) approach. The agreement between the calibration systems and experiment is very good. The computed values for 1-butene are compared with calibration systems and the agreement between the computed results for 1-butene and the "rule of thumb" values from the smaller systems is remarkably good.

  5. Activation of C-O and C-C bonds and formation of novel HAlOH-ether complexes: an EPR study of the reaction of ground-state Al atoms with methylethyl ether and diethyl ether.

    PubMed

    Brunet, Franois D; Feola, Julie C; Joly, Helen A

    2012-03-15

    Reaction mixtures, containing Al atoms and methylethyl ether (MEE) or diethyl ether (DEE) in an adamantane matrix, were prepared with the aid of a metal-atom reactor known as a rotating cryostat. The EPR spectra of the resulting products were recorded from 77-260 K, at 10 K intervals. Al atoms were found to insert into methyl-O, ethyl-O, and C-C bonds to form CH(3)AlOCH(2)CH(3), CH(3)OAlCH(2)CH(3), and CH(3)OCH(2)AlCH(3), respectively, in the case of MEE while DEE produced CH(3)CH(2)AlOCH(2)CH(3) and CH(3)AlCH(2)OCH(2)CH(3), respectively. From the intensity of the transition lines attributed to the Al atom C-O insertion products of MEE, insertion into the methyl-O bond is preferred. The Al hyperfine interaction (hfi) extracted from the EPR spectra of the C-O insertion products was greater than that of the C-C insertion products, that is, 5.4% greater for the DEE system and 7% greater for the MEE system. The increase in Al hfi is thought to arise from the increased electron-withdrawing ability of the substituents bonded to Al. Besides HAlOH, resulting from the reaction of Al atoms with adventitious water, novel mixed HAlOH:MEE and HAlOH:DEE complexes were identified with the aid of isotopic studies involving H(2)(17)O and D(2)O. The Al and H hfi of HAlOH were found to decrease upon complex formation. These findings are consistent with the nuclear hfi calculated using a density functional theory (DFT) method with close agreement between theory and experiment occurring at the B3LYP level using a 6-311+G(2df,p) basis set. PMID:22299675

  6. Temperature effects on adsorption and diffusion dynamics of CH3CH2(ads) and H3C-C?C(ads) on Ag(111) surface and their self-coupling reactions: ab initio molecular dynamics approach.

    PubMed

    Lu, Shao-Yu; Lin, Jyh-Shing

    2014-01-14

    Density functional theory (DFT)-based molecular dynamics (DFTMD) simulations in combination with a Fourier transform of dipole moment autocorrelation function are performed to investigate the adsorption dynamics and the reaction mechanisms of self-coupling reactions of both acetylide (H3C-C(?)?C(?) (ads)) and ethyl (H3C(?)-C(?)H2(ads)) with I(ads) coadsorbed on the Ag(111) surface at various temperatures. In addition, the calculated infrared spectra of H3C-C(?)?C(?)(ads) and I coadsorbed on the Ag(111) surface indicate that the active peaks of -C(?)?C(?)- stretching are gradually merged into one peak as a result of the dominant motion of the stand-up -C-C(?)?C(?)- axis as the temperature increases from 200 K to 400 K. However, the calculated infrared spectra of H3C(?)-C(?)H2(ads) and I coadsorbed on the Ag(111) surface indicate that all the active peaks are not altered as the temperature increases from 100 K to 150 K because only one orientation of H3C(?)-C(?)H2(ads) adsorbed on the Ag(111) surface has been observed. These calculated IR spectra are in a good agreement with experimental reflection absorption infrared spectroscopy results. Furthermore, the dynamics behaviors of H3C-C(?)?C(?)(ads) and I coadsorbed on the Ag(111) surface point out the less diffusive ability of H3C-C(?)?C(?)(ads) due to the increasing s-character of C? leading to the stronger Ag-C? bond in comparison with that of H3C(?)-C(?)H2(ads) and I coadsorbed on the same surface. Finally, these DFTMD simulation results allow us to predict the energetically more favourable reaction pathways for self-coupling of both H3C-C(?)?C(?)(ads) and H3C(?)-C(?)H2(ads) adsorbed on the Ag(111) surface to form 2,4-hexadiyne (H3C-C?C-C?C-CH3(g)) and butane (CH3-CH2-CH2-CH3(g)), respectively. The calculated reaction energy barriers for both H3C-C?C-C?C-CH3(g) (1.34 eV) and CH3-CH2-CH2-CH3(g) (0.60 eV) are further employed with the Redhead analysis to estimate the desorption temperatures approximately at 510 K and 230 K, respectively, which are in a good agreement with the experimental low-coverage temperature programmed reaction spectroscopy measurements. PMID:24437901

  7. Temperature effects on adsorption and diffusion dynamics of CH3CH2(ads) and H3C-C?C(ads) on Ag(111) surface and their self-coupling reactions: Ab initio molecular dynamics approach

    NASA Astrophysics Data System (ADS)

    Lu, Shao-Yu; Lin, Jyh-Shing

    2014-01-01

    Density functional theory (DFT)-based molecular dynamics (DFTMD) simulations in combination with a Fourier transform of dipole moment autocorrelation function are performed to investigate the adsorption dynamics and the reaction mechanisms of self-coupling reactions of both acetylide (H3C-C(?)?C(?) (ads)) and ethyl (H3C(?)-C(?)H2(ads)) with I(ads) coadsorbed on the Ag(111) surface at various temperatures. In addition, the calculated infrared spectra of H3C-C(?)?C(?)(ads) and I coadsorbed on the Ag(111) surface indicate that the active peaks of -C(?)?C(?)- stretching are gradually merged into one peak as a result of the dominant motion of the stand-up -C-C(?)?C(?)- axis as the temperature increases from 200 K to 400 K. However, the calculated infrared spectra of H3C(?)-C(?)H2(ads) and I coadsorbed on the Ag(111) surface indicate that all the active peaks are not altered as the temperature increases from 100 K to 150 K because only one orientation of H3C(?)-C(?)H2(ads) adsorbed on the Ag(111) surface has been observed. These calculated IR spectra are in a good agreement with experimental reflection absorption infrared spectroscopy results. Furthermore, the dynamics behaviors of H3C-C(?)?C(?)(ads) and I coadsorbed on the Ag(111) surface point out the less diffusive ability of H3C-C(?)?C(?)(ads) due to the increasing s-character of C? leading to the stronger Ag-C? bond in comparison with that of H3C(?)-C(?)H2(ads) and I coadsorbed on the same surface. Finally, these DFTMD simulation results allow us to predict the energetically more favourable reaction pathways for self-coupling of both H3C-C(?)?C(?)(ads) and H3C(?)-C(?)H2(ads) adsorbed on the Ag(111) surface to form 2,4-hexadiyne (H3C-C?C-C?C-CH3(g)) and butane (CH3-CH2-CH2-CH3(g)), respectively. The calculated reaction energy barriers for both H3C-C?C-C?C-CH3(g) (1.34 eV) and CH3-CH2-CH2-CH3(g) (0.60 eV) are further employed with the Redhead analysis to estimate the desorption temperatures approximately at 510 K and 230 K, respectively, which are in a good agreement with the experimental low-coverage temperature programmed reaction spectroscopy measurements.

  8. A calculation of the diffusion energies for adatoms on surfaces of F.C.C. metals

    NASA Technical Reports Server (NTRS)

    Halicioglu, T.; Pound, G. M.

    1979-01-01

    The activation energies for diffusion were determined for gold, platinum and iridium adatoms on plane and plane PT surfaces and were found to be in good agreement with the measurements reported by Bassett and Webber. The Lennard-Jones pair potentials were used to model the interatomic forces, and relaxation of the substrate atoms in near proximity to the adatom was considered in detail. The present calculations clarify the mechanism of the observed two-dimensional diffusion of platinum and iridium atoms on a plane PT surface. The results are compared with those obtained using Morse potential functions and different relaxation techniques.

  9. Kinetic and Structural Insight into the Mechanism of BphD, a C-C Bond Hydrolase from the Biphenyl Degradation Pathway

    PubMed Central

    Horsman, Geoff P.; Ke, Jiyuan; Dai, Shaodong; Seah, Stephen Y. K.; Bolin, Jeffrey T.; Eltis, Lindsay D.

    2008-01-01

    Kinetic and structural analyses of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid (HOPDA) hydrolase from Burkholderia xenovorans LB400 (BphDLB400) provide insight into the catalytic mechanism of this unusual serine hydrolase. Single turnover stopped-flow analysis at 25 C showed that the enzyme rapidly (1/?1 ? 500 s?1) transforms HOPDA (?max = 434 nm) to a species with electronic absorption maxima at 473 and 492 nm. The absorbance of this enzyme-bound species (E:S) decayed in a biphasic manner (1/?2 = 54 s?1, 1/?3 = 6 s?1 ? kcat) with simultaneous biphasic appearance (48 and 8 s?1) of an absorbance band at 270 nm characteristic of one of the products, 2-hydroxypenta-2,4-dienoic acid (HPD). Increasing solution viscosity with glycerol slowed 1/?1 and 1/?2, but affected neither 1/?3 nor kcat, suggesting that 1/?2 may reflect diffusive HPD dissociation, while 1/?3 represents an intramolecular event. Product inhibition studies suggested that the other product, benzoate, is released after HPD. Contrary to studies in a related hydrolase, we found no evidence that ketonized HOPDA is partially released prior to hydrolysis, and therefore postulate that the biphasic kinetics reflect one of two mechanisms, pending assignment of E:S (?max = 492 nm). Crystal structures of wild type, the S112C variant, and S112C incubated with HOPDA were each determined to 1.6 resolution. The latter reveals interactions between conserved active site residues and the dienoate moiety of the substrate. Most notably, the catalytic residue His265 is hydrogen-bonded to the 2-hydroxy/oxo substituent of HOPDA, consistent with a role in catalyzing ketonization. The data are more consistent with an acyl-enzyme mechanism than with the formation of a gem-diol intermediate. PMID:16964968

  10. Synthesis of seco-B-Ring Bryostatin Analogue WN-1 via CC Bond-Forming Hydrogenation: Critical Contribution of the B-Ring in Determining Bryostatin-like and Phorbol 12-Myristate 13-Acetate-like Properties

    PubMed Central

    2015-01-01

    The seco-B-ring bryostatin analogue, macrodiolide WN-1, was prepared in 17 steps (longest linear sequence) and 30 total steps with three bonds formed via hydrogen-mediated CC coupling. This synthetic route features a palladium-catalyzed alkoxycarbonylation of a C2-symmetric diol to form the C9-deoxygenated bryostatin A-ring. WN-1 binds to PKC? (Ki = 16.1 nM) and inhibits the growth of multiple leukemia cell lines. Although structural features of the WN-1 A-ring and C-ring are shared by analogues that display bryostatin-like behavior, WN-1 displays PMA-like behavior in U937 cell attachment and proliferation assays, as well as in K562 and MV-4-11 proliferation assays. Molecular modeling studies suggest the pattern of internal hydrogen bonds evident in bryostatin 1 is preserved in WN-1, and that upon docking WN-1 into the crystal structure of the C1b domain of PKC?, the binding mode of bryostatin 1 is reproduced. The collective data emphasize the critical contribution of the B-ring to the function of the upper portion of the molecule in conferring a bryostatin-like pattern of biological activity. PMID:25207655

  11. Synthesis of seco-B-ring bryostatin analogue WN-1 via C-C bond-forming hydrogenation: critical contribution of the B-ring in determining bryostatin-like and phorbol 12-myristate 13-acetate-like properties.

    PubMed

    Andrews, Ian P; Ketcham, John M; Blumberg, Peter M; Kedei, Noemi; Lewin, Nancy E; Peach, Megan L; Krische, Michael J

    2014-09-24

    The seco-B-ring bryostatin analogue, macrodiolide WN-1, was prepared in 17 steps (longest linear sequence) and 30 total steps with three bonds formed via hydrogen-mediated C-C coupling. This synthetic route features a palladium-catalyzed alkoxycarbonylation of a C2-symmetric diol to form the C9-deoxygenated bryostatin A-ring. WN-1 binds to PKC? (Ki = 16.1 nM) and inhibits the growth of multiple leukemia cell lines. Although structural features of the WN-1 A-ring and C-ring are shared by analogues that display bryostatin-like behavior, WN-1 displays PMA-like behavior in U937 cell attachment and proliferation assays, as well as in K562 and MV-4-11 proliferation assays. Molecular modeling studies suggest the pattern of internal hydrogen bonds evident in bryostatin 1 is preserved in WN-1, and that upon docking WN-1 into the crystal structure of the C1b domain of PKC?, the binding mode of bryostatin 1 is reproduced. The collective data emphasize the critical contribution of the B-ring to the function of the upper portion of the molecule in conferring a bryostatin-like pattern of biological activity. PMID:25207655

  12. Do Bond Functions Help for the Calculation of Accurate Bond Energies?

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Arnold, James (Technical Monitor)

    1998-01-01

    The bond energies of 8 chemically bound diatomics are computed using several basis sets with and without bond functions (BF). The bond energies obtained using the aug-pVnZ+BF basis sets (with a correction for basis set superposition error, BSSE) tend to be slightly smaller that the results obtained using the aug-pV(n+I)Z basis sets, but slightly larger than the BSSE corrected aug-pV(n+I)Z results. The aug-cc-pVDZ+BF and aug-cc-pVTZ+BF basis sets yield reasonable estimates of bond energies, but, in most cases, these results cannot be considered highly accurate. Extrapolation of the results obtained with basis sets including bond functions appears to be inferior to the results obtained by extrapolation using atom-centered basis sets. Therefore bond functions do not appear to offer a path for obtaining highly accurate results for chemically bound systems at a lower computational cost than atom centered basis sets.

  13. The Calculation of Accurate Metal-Ligand Bond Energies

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W.; Partridge, Harry, III; Ricca, Alessandra; Arnold, James O. (Technical Monitor)

    1997-01-01

    The optimization of the geometry and calculation of zero-point energies are carried out at the B3LYP level of theory. The bond energies are determined at this level, as well as at the CCSD(T) level using very large basis sets. The successive OH bond energies to the first row transition metal cations are reported. For most systems there has been an experimental determination of the first OH. In general, the CCSD(T) values are in good agreement with experiment. The bonding changes from mostly covalent for the early metals to mostly electrostatic for the late transition metal systems.

  14. Estimation of Bond Dissociation Energies and Radical Stabilization Energies by ESR Spectroscopy

    E-print Network

    Brocks, Jochen J.

    Estimation of Bond Dissociation Energies and Radical Stabilization Energies by ESR Spectroscopy stabilization enthalpies (RSE) and with BDE(C-H), the C-H bond dissociation energies for the corresponding stabilization energies and bond dissociation enthalpies (BDE) are useful for the prediction or inter- pretation

  15. Various Carbon to Carbon Bond Lengths Inter-related via the Golden Ratio, and their Linear Dependence on Bond Energies

    E-print Network

    Raji Heyrovska

    2008-09-11

    This work presents the relations between the carbon to carbon bond lengths in the single, double and triple bonds and in graphite, butadiene and benzene. The Golden ratio, which was shown to divide the Bohr radius into two parts pertaining to the charged particles, the electron and proton, and to divide inter-atomic distances into their cationic and anionic radii, also plays a role in the carbon-carbon bonds and in the ionic/polar character of those in graphite, butadiene and benzene. Further, the bond energies of the various CC bonds are shown to vary linearly with the bond lengths.

  16. How resonance assists hydrogen bonding interactions: an energy decomposition analysis.

    PubMed

    Beck, John Frederick; Mo, Yirong

    2007-01-15

    Block-localized wave function (BLW) method, which is a variant of the ab initio valence bond (VB) theory, was employed to explore the nature of resonance-assisted hydrogen bonds (RAHBs) and to investigate the mechanism of synergistic interplay between pi delocalization and hydrogen-bonding interactions. We examined the dimers of formic acid, formamide, 4-pyrimidinone, 2-pyridinone, 2-hydroxpyridine, and 2-hydroxycyclopenta-2,4-dien-1-one. In addition, we studied the interactions in beta-diketone enols with a simplified model, namely the hydrogen bonds of 3-hydroxypropenal with both ethenol and formaldehyde. The intermolecular interaction energies, either with or without the involvement of pi resonance, were decomposed into the Hitler-London energy (DeltaEHL), polarization energy (DeltaEpol), charge transfer energy (DeltaECT), and electron correlation energy (DeltaEcor) terms. This allows for the examination of the character of hydrogen bonds and the impact of pi conjugation on hydrogen bonding interactions. Although it has been proposed that resonance-assisted hydrogen bonds are accompanied with an increasing of covalency character, our analyses showed that the enhanced interactions mostly originate from the classical dipole-dipole (i.e., electrostatic) attraction, as resonance redistributes the electron density and increases the dipole moments in monomers. The covalency of hydrogen bonds, however, changes very little. This disputes the belief that RAHB is primarily covalent in nature. Accordingly, we recommend the term "resonance-assisted binding (RAB)" instead of "resonance-assisted hydrogen bonding (RHAB)" to highlight the electrostatic, which is a long-range effect, rather than the electron transfer nature of the enhanced stabilization in RAHBs. PMID:17143867

  17. The Tautomeric Half-reaction of BphD, a C-C Bond Hydrolase Kinetic and Structural Evidence Supporting a Key Role for Histidine 265 of the Catalytic triad

    SciTech Connect

    Horsman, Geoff P.; Bhowmik, Shiva; Seah, Stephen Y.K.; Kumar, Pravindra; Bolin, Jeffrey T.; Eltis, Lindsay D.

    2010-01-07

    BphD of Burkholderia xenovorans LB400 catalyzes an unusual C-C bond hydrolysis of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid (HOPDA) to afford benzoic acid and 2-hydroxy-2,4-pentadienoic acid (HPD). An enol-keto tautomerization has been proposed to precede hydrolysis via a gem-diol intermediate. The role of the canonical catalytic triad (Ser-112, His-265, Asp-237) in mediating these two half-reactions remains unclear. We previously reported that the BphD-catalyzed hydrolysis of HOPDA ({lambda}{sub max} is 434 nm for the free enolate) proceeds via an unidentified intermediate with a red-shifted absorption spectrum ({lambda}{sub max} is 492 nm) (Horsman, G. P., Ke, J., Dai, S., Seah, S. Y. K., Bolin, J. T., and Eltis, L. D. (2006) Biochemistry 45, 11071-11086). Here we demonstrate that the S112A variant generates and traps a similar intermediate ({lambda}{sub max} is 506 nm) with a similar rate, 1/{tau} {approx} 500 s{sup -1}. The crystal structure of the S112A:HOPDA complex at 1.8-{angstrom} resolution identified this intermediate as the keto tautomer, (E)-2,6-dioxo-6-phenyl-hex-3-enoate. This keto tautomer did not accumulate in either the H265A or the S112A/H265A double variants, indicating that His-265 catalyzes tautomerization. Consistent with this role, the wild type and S112A enzymes catalyzed tautomerization of the product HPD, whereas H265A variants did not. This study thus identifies a keto intermediate, and demonstrates that the catalytic triad histidine catalyzes the tautomerization half-reaction, expanding the role of this residue from its purely hydrolytic function in other serine hydrolases. Finally, the S112A:HOPDA crystal structure is more consistent with hydrolysis occurring via an acyl-enzyme intermediate than a gem-diol intermediate as solvent molecules have poor access to C6, and the closest ordered water is 7{angstrom} away.

  18. Students' Interdisciplinary Reasoning about "High-Energy Bonds" and ATP

    E-print Network

    Dreyfus, Benjamin W; Sawtelle, Vashti; Svoboda, Julia; Turpen, Chandra; Redish, Edward F

    2012-01-01

    Students' sometimes contradictory ideas about ATP (adenosine triphosphate) and the nature of chemical bonds have been studied in the biology and chemistry education literatures, but these topics are rarely part of the introductory physics curriculum. We present qualitative data from an introductory physics course for undergraduate biology majors that seeks to build greater interdisciplinary coherence and therefore includes these topics. In these data, students grapple with the apparent contradiction between the energy released when the phosphate bond in ATP is broken and the idea that an energy input is required to break a bond. We see that students' perceptions of how each scientific discipline bounds the system of interest can influence how they justify their reasoning about a topic that crosses disciplines. This has consequences for a vision of interdisciplinary education that respects disciplinary perspectives while bringing them into interaction in ways that demonstrate consistency amongst the perspectiv...

  19. Storing Renewable Energy in Chemical Bonds

    SciTech Connect

    Helm, Monte; Bullock, Morris

    2013-03-27

    With nearly 7 billion people, the world's population is demanding more electricity every year. Improved technologies are bringing wind and solar power to our electrical grid. However, wind turbines and solar panels only work when the wind blows or the sun shines. PNNL scientists discuss catalysis approaches for storing and releasing energy on demand.

  20. Storing Renewable Energy in Chemical Bonds

    ScienceCinema

    Helm, Monte; Bullock, Morris

    2014-06-13

    With nearly 7 billion people, the world's population is demanding more electricity every year. Improved technologies are bringing wind and solar power to our electrical grid. However, wind turbines and solar panels only work when the wind blows or the sun shines. PNNL scientists discuss catalysis approaches for storing and releasing energy on demand.

  1. Bond Dissociation Energies for Substituted Polycyclic Aromatic Hydrocarbons and Their Cations

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W.; Langhoff, Stephen R.; Arnold, James O. (Technical Monitor)

    1998-01-01

    The B3LYP/4-31G approach is used to compute bond energies for a series of substituted benzene, naphthalene, and anthracene molecules and their cations. The benzene bond energies are compared with experiment. The trends in the bond energies are discussed. The ionization energies are also reported and compared with available experiments.

  2. Bond length and local energy density property connections for non-transition-metal oxide-bonded interactions.

    PubMed

    Gibbs, G V; Spackman, M A; Jayatilaka, D; Rosso, K M; Cox, D F

    2006-11-01

    For a variety of molecules and earth materials, the theoretical local kinetic energy density, G(r(c)), increases and the local potential energy density, V(r(c)), decreases as the M-O bond lengths (M = first- and second-row metal atoms bonded to O) decrease and the electron density, rho(r(c)), accumulates at the bond critical points, r(c). Despite the claim that the local kinetic energy density per electronic charge, G(r(c))/rho(r(c)), classifies bonded interactions as shared interactions when less than unity and closed-shell when greater, the ratio was found to increase from 0.5 to 2.5 au as the local electronic energy density, H(r(c)) = G(r(c)) + V(r(c)), decreases and becomes progressively more negative. The ratio appears to be a measure of the character of a given M-O bonded interaction, the greater the ratio, the larger the value of rho(r(c)), the smaller the coordination number of the M atom and the more shared the bonded interaction. H(r(c))/rho(r(c)) versus G(r(c))/rho(r(c)) scatter diagrams categorize the M-O bonded interactions into domains with the local electronic energy density per electron charge, H(r(c))/rho(r(c)), tending to decrease as the electronegativity differences for the bonded pairs of atoms decrease. The values of G(r(c)) and V(r(c)), estimated with a gradient-corrected electron gas theory expression and the local virial theorem, are in good agreement with theoretical values, particularly for the bonded interactions involving second-row M atoms. The agreement is poorer for shared C-O and N-O bonded interactions. PMID:17078623

  3. Argon hydrochloride, Ar.HCl, bond energy by infrared spectroscopy

    NASA Technical Reports Server (NTRS)

    Miziolek, A. W.; Pimentel, G. C.

    1976-01-01

    The infrared absorption of argon (200 to 760 torr) and hydrogen chloride (2 to 6 torr) mixtures is reexamined in the missing Q branch region (spectral region between 2860 and 3010 wavelength/cm) at temperatures ranging from 195 to 298 K. The temperature dependence of two absorption features of the argon hydrogen chloride complex, at 2887 and 2879 wavelength/cm, leads to a bond energy estimate that depends on the assumptions made about the internal degrees of freedom of the complex. It is shown that agreement with experiment can be reached for well depths near 1.2 kcal/mole. This result is relatively insensitive to the choice of the vibrational frequencies and anharmonicities, but does depend on the extent to which the energy level manifolds are truncated to avoid molecular excitation in excess of the bond energy. The bond energy is found to deviate from the commonly accepted value of 0.4 kcal/mole. Possible causes for the discrepancy are considered.

  4. Energy-based analysis of biochemical cycles using bond graphs.

    PubMed

    Gawthrop, Peter J; Crampin, Edmund J

    2014-11-01

    Thermodynamic aspects of chemical reactions have a long history in the physical chemistry literature. In particular, biochemical cycles require a source of energy to function. However, although fundamental, the role of chemical potential and Gibb's free energy in the analysis of biochemical systems is often overlooked leading to models which are physically impossible. The bond graph approach was developed for modelling engineering systems, where energy generation, storage and transmission are fundamental. The method focuses on how power flows between components and how energy is stored, transmitted or dissipated within components. Based on the early ideas of network thermodynamics, we have applied this approach to biochemical systems to generate models which automatically obey the laws of thermodynamics. We illustrate the method with examples of biochemical cycles. We have found that thermodynamically compliant models of simple biochemical cycles can easily be developed using this approach. In particular, both stoichiometric information and simulation models can be developed directly from the bond graph. Furthermore, model reduction and approximation while retaining structural and thermodynamic properties is facilitated. Because the bond graph approach is also modular and scaleable, we believe that it provides a secure foundation for building thermodynamically compliant models of large biochemical networks. PMID:25383030

  5. Energy-based analysis of biochemical cycles using bond graphs

    PubMed Central

    Gawthrop, Peter J.; Crampin, Edmund J.

    2014-01-01

    Thermodynamic aspects of chemical reactions have a long history in the physical chemistry literature. In particular, biochemical cycles require a source of energy to function. However, although fundamental, the role of chemical potential and Gibb's free energy in the analysis of biochemical systems is often overlooked leading to models which are physically impossible. The bond graph approach was developed for modelling engineering systems, where energy generation, storage and transmission are fundamental. The method focuses on how power flows between components and how energy is stored, transmitted or dissipated within components. Based on the early ideas of network thermodynamics, we have applied this approach to biochemical systems to generate models which automatically obey the laws of thermodynamics. We illustrate the method with examples of biochemical cycles. We have found that thermodynamically compliant models of simple biochemical cycles can easily be developed using this approach. In particular, both stoichiometric information and simulation models can be developed directly from the bond graph. Furthermore, model reduction and approximation while retaining structural and thermodynamic properties is facilitated. Because the bond graph approach is also modular and scaleable, we believe that it provides a secure foundation for building thermodynamically compliant models of large biochemical networks. PMID:25383030

  6. IR Spectra and Bond Energies Computed Using DFT

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles; Andrews, Lester; Arnold, James (Technical Monitor)

    2000-01-01

    The combination of density functional theory (DFT) frequencies and infrared (IR) intensities and experimental spectra is a very powerful tool in the identification of molecules and ions. The computed and measured isotopic ratios make the identification much more secure than frequencies and intensities alone. This will be illustrated using several examples, such as Mn(CO)n and Mn(CO)n-. The accuracy of DFT metal-ligand bond energies will also be discussed.

  7. Analysis of liquid metal embrittlement from a bond energy viewpoint

    NASA Technical Reports Server (NTRS)

    Kelley, M. J.; Stoloff, N. S.

    1975-01-01

    Absorption induced embrittlement of solid metals by certain liquid metals is analyzed through an Engel-Brewer calculation of the solid-liquid interaction energy, and of the effect of the latter in reducing fracture surface energy. The reduction in fracture surface energy is estimated by comparison of the electronic contribution to the solid-liquid interaction energy with solid-solid bond energy for some 40 liquid-solid couples. Regular solution theory is used to estimate mutual solubility as the relative difference in parameter values. Embrittlement can be predicted by using reduction in fracture surface energy and solubility parameter difference as critical variables. The effect of solute additions to the liquid on the degree of embrittlement is interpreted via the same two variables; the principal effect of solutes is to modify solubility relationships at the solid-liquid interface.

  8. Bond Energies in Models of the Schrock Metathesis Catalyst

    SciTech Connect

    Vasiliu, Monica; Li, Shenggang; Arduengo, Anthony J.; Dixon, David A.

    2011-06-02

    Heats of formation, adiabatic and diabatic bond dissociation energies (BDEs) of the model Schrock-type metal complexes M(NH)(CRR?)(OH)? (M = Cr, Mo, W; CRR? = CH?, CHF, CF?) and MO?(OH)? compounds, and Brnsted acidities and fluoride affinities for the M(NH)(CH?)(OH) ? transition metal complexes are predicted using high level CCSD(T) calculations. The metallacycle intermediates formed by reaction of C?H4 with M(NH)-(CH?)(OH)2 and MO?(OH)? are investigated at the same level of theory. Additional corrections were added to the complete basis set limit to obtain near chemical accuracy ((1 kcal/mol). A comparison between adiabatic and diabatic BDEs is made and provides an explanation of trends in the BDEs. Electronegative groups bonded on the carbenic carbon lead to less stable Schrock-type complexes as the adiabatic BDEs ofMdCF? andMdCHF bonds are much lower than theMdCH? bonds. The Cr compounds have smaller BDEs than theWorMo complexes and should be less stable. Different M(NH)(OH)?(C?H?) and MO(OH)?(OC?H4) metallacycle intermediates are investigated, and the lowest-energy metallacycles have a square pyramidal geometry. The results show that consideration of the singlet_triplet splitting in the carbene in the initial catalyst as well as in the metal product formed by the retro [2+2] cycloaddition is a critical component in the design of an effective olefin metathesis catalyst in terms of the parent catalyst and the groups being transferred.

  9. Effects of Exchange Energy and Spin-Orbit Coupling on Bond Energies

    ERIC Educational Resources Information Center

    Smith, Derek W.

    2004-01-01

    Since chemical reactions involve the breaking and making of bonds, understanding the relative strengths of bonds is of paramount importance in the study, teaching, and practice of chemistry. Further, it is showed that free atoms having p(super n) configuration with n = 2,3, or 4 are stabilized by exchange energy, and by spin-orbit coupling for n =

  10. Superplastic deformation and energy dissipation mechanism in surface-bonded carbon nanofibers

    E-print Network

    Sansoz, Frederic

    Superplastic deformation and energy dissipation mechanism in surface-bonded carbon nanofibers 12 December 2014 Accepted 20 December 2014 Keywords: Carbon nanofibers Superplasticity Fracture mechanisms in cone-stacked carbon nanofibers. The sim- ulations predict that the surface bond density

  11. Controlling the bond scission sequence of oxygenates for energy applications

    NASA Astrophysics Data System (ADS)

    Stottlemyer, Alan L.

    The so called "Holy Grail" of heterogeneous catalysis is a fundamental understanding of catalyzed chemical transformations which span multidimensional scales of both length and time, enabling rational catalyst design. Such an undertaking is realizable only with an atomic level understanding of bond formation and destruction with respect to intrinsic properties of the metal catalyst. In this study, we investigate the bond scission sequence of small oxygenates (methanol, ethanol, ethylene glycol) on bimetallic transition metal catalysts and transition metal carbide catalysts. Oxygenates are of interest both as hydrogen carriers for reforming to H2 and CO and as fuels in direct alcohol fuel cells (DAFC). To address the so-called "materials gap" and "pressure gap" this work adopted three parallel research approaches: (1) ultra high vacuum (UHV) studies including temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) on polycrystalline surfaces; (2) DFT studies including thermodynamic and kinetic calculations; (3) electrochemical studies including cyclic voltammetry (CV) and chronoamperometry (CA). Recent studies have suggested that tungsten monocarbide (WC) may behave similarly to Pt for the electrooxidation of oxygenates. TPD was used to quantify the activity and selectivity of oxygenate decomposition for WC and Pt-modifiedWC (Pt/WC) as compared to Pt. While decomposition activity was generally higher on WC than on Pt, scission of the C-O bond resulted in alkane/alkene formation on WC, an undesired product for DAFC. When Pt was added to WC by physical vapor deposition C-O bond scission was limited, suggesting that Pt synergistically modifies WC to improve the selectivity toward C-H bond scission to produce H2 and CO. Additionally, TPD confirmed WC and Pt/WC to be more CO tolerant than Pt. HREELS results verified that surface intermediates were different on Pt/WC as compared to Pt or WC and evidence of aldehyde intermediates was observed on the Pt and Pt/WC surfaces. For CH3OH decomposition, DFT calculations suggested that the bond scission sequence could be controlled using monolayer coverage of Pt on WC. The Ni/Pt bimetallic system was studied as an example for using oxygenates as a hydrogen source. There are two well characterized surface structures for the Ni/Pt system: the surface configuration, in which the Ni atoms reside primarily on the surface of the Pt bulk, and the subsurface configuration, in which the second atomic layer is enriched in Ni atoms and the surface is enriched in Pt atoms. These configurations are denoted NiPtPt and PtNiPt, respectively. DFT results revealed that trends established for the Ni/Pt(111) system extend to the Ni/Pt(100) analogue. TPD studies revealed that the NiPtPt surface was more active for oxygenate reforming than the Pt or PtNiPt surfaces. HREELS confirmed the presence of strongly bound reaction intermediates, including aldehyde-like species, and suggested that the first decomposition step was likely O-H bond scission. Thus, the binding energies of the deprotonated reaction intermediates are important parameters in controlling the decomposition pathways of oxygenates. These studies have demonstrated that the bond scission sequence of oxygenate decomposition can be controlled using bimetallic and transition metal carbide catalysts. While this study has focused on oxygenate decomposition for energy applications, the principles and methodology applied herein are universally applicable to the development of novel and marketable value-added products. The value in such a methodology is in the combination of both calculations to predict catalytic and chemical properties, and experiments to fine-tune theoretical predictions.

  12. B r y n S a d o w n i k , M a r k J a c c a r d Shaping Sustainable Energy Use in Chinese Cities

    E-print Network

    B r y n S a d o w n i k , M a r k J a c c a r d Shaping Sustainable Energy Use in Chinese Cities is predetermined when land-use and urban form are designated. Community Energy Management (CEM) is a sustainable: for instance, cities that more closely integrate residential and commercial activities in higher densities

  13. Ubiquitous Transgenic Overexpression of C-C Chemokine Ligand 2: A Model to Assess the Combined Effect of High Energy Intake and Continuous Low-Grade Inflammation

    PubMed Central

    Rodrguez-Gallego, Esther; Hernndez-Aguilera, Anna; Marin-Casad, Roger; Rull, Anna; Beltrn-Debn, Ral; Menendez, Javier A.; Vazquez-Martin, Alejandro; Sirvent, Juan J.; Martn-Paredero, Vicente; Corb, Angel L.; Sierra-Filardi, Elena; Aragons, Gerard; Garca-Heredia, Anabel; Camps, Jordi; Alonso-Villaverde, Carlos; Joven, Jorge

    2013-01-01

    Excessive energy management leads to low-grade, chronic inflammation, which is a significant factor predicting noncommunicable diseases. In turn, inflammation, oxidation, and metabolism are associated with the course of these diseases; mitochondrial dysfunction seems to be at the crossroads of mutual relationships. The migration of immune cells during inflammation is governed by the interaction between chemokines and chemokine receptors. Chemokines, especially C-C-chemokine ligand 2 (CCL2), have a variety of additional functions that are involved in the maintenance of normal metabolism. It is our hypothesis that a ubiquitous and continuous secretion of CCL2 may represent an animal model of low-grade chronic inflammation that, in the presence of an energy surplus, could help to ascertain the afore-mentioned relationships and/or to search for specific therapeutic approaches. Here, we present preliminary data on a mouse model created by using targeted gene knock-in technology to integrate an additional copy of the CCl2 gene in the Gt(ROSA)26Sor locus of the mouse genome via homologous recombination in embryonic stem cells. Short-term dietary manipulations were assessed and the findings include metabolic disturbances, premature death, and the manipulation of macrophage plasticity and autophagy. These results raise a number of mechanistic questions for future study. PMID:24453432

  14. Theoretical determination of the alkali-metal superoxide bond energies

    NASA Technical Reports Server (NTRS)

    Partridge, Harry; Bauschlicher, Charles W., Jr.; Sodupe, Mariona; Langhoff, Stephen R.

    1992-01-01

    The bond dissociation energies for the alkali-metal superoxides have been computed using extensive Gaussian basis sets and treating electron correlation at the modified coupled-pair functional level. Our computed D0 values are 61.4, 37.2, 40.6, and 38.4 kcal/mol for LiO2, NaO2, KO2, and RbO2, respectively. These values, which are expected to be lower bounds and accurate to 2 kcal/mol, agree well with some of the older flame data, but rule out several recent experimental measurements.

  15. Mediatorless solar energy conversion by covalently bonded thylakoid monolayer on the glassy carbon electrode.

    PubMed

    Lee, Jinhwan; Im, Jaekyun; Kim, Sunghyun

    2016-04-01

    Light reactions of photosynthesis that take place in thylakoid membranes found in plants or cyanobacteria are among the most effective ways of utilizing light. Unlike most researches that use photosystem I or photosystem II as conversion units for converting light to electricity, we have developed a simple method in which the thylakoid monolayer was covalently immobilized on the glassy carbon electrode surface. The activity of isolated thylakoid membrane was confirmed by measuring evolving oxygen under illumination. Glassy carbon surfaces were first modified with partial or full monolayers of carboxyphenyl groups by reductive C-C coupling using 4-aminobenzoic acid and aniline and then thylakoid membrane was bioconjugated through the peptide bond between amine residues of thylakoid and carboxyl groups on the surface. Surface properties of modified surfaces were characterized by cyclic voltammetry, contact angle measurements, and electrochemical impedance spectroscopy. Photocurrent of 230nAcm(-2) was observed when the thylakoid monolayer was formed on the mixed monolayer of 4-carboxylpheny and benzene at applied potential of 0.4V vs. Ag/AgCl. A small photocurrent resulted when the 4-carboxyphenyl full monolayer was used. This work shows the possibility of solar energy conversion by directly employing the whole thylakoid membrane through simple surface modification. PMID:26625272

  16. Tubulin Bond Energies and Microtubule Biomechanics Determined from Nanoindentation in Silico

    E-print Network

    Barsegov, Valeri

    Tubulin Bond Energies and Microtubule Biomechanics Determined from Nanoindentation in Silico Olga, are stabilized by longitudinal and lateral noncovalent bonds between the tubulin subunits. However (14.9 1.5 kcal/mol) tubulin-tubulin bonds. These values in conjunction with the large flexural

  17. A Dynamic Pathway for Stone-Wales Bond Rotation on Carbon Nanotubes through Diamond-Like Bonds

    NASA Technical Reports Server (NTRS)

    Wei, Chen-Yu; Srivastava, Deepak; Cho, Kyeong-Jae; Menon, Madhu

    2003-01-01

    A new lower energy barrier with a two-step pathway of Stone-Wales (SW) ,ond rotation on carbon nanotubes (CNTs) is found through molecular dynamics (MD) simulations of CNTs under tension. The first step involves going over to a stable sp3-like metastable configuration with half rotated and partially tilted C-C bond. The second step involves going over to the fully rotated C-C bond with the formation of a SW defect in the nanotube. The energy barrier for this two-step dynamic pathway is significantly lower than the previously known static barrier for in-plane rotation of the C-C bond on a tensile strained (> 4%) CNT.

  18. Classification of metal-oxide bonded interactions based on local potential- and kinetic-energy densities

    SciTech Connect

    Gibbs, Gerald V.; Cox, David; Crawford, T Daniel; Rosso, Kevin M.; Ross, Nancy; Downs, R. T.

    2006-02-28

    A classification of the HF bonded interactions comprising a large number of molecules has been proposed by Espinosa et al. [J. Chem. Phys. 117, 5529 (2002)] based on the ratio |V(rc)|/G(rc) where |V(rc)| is the magnitude of the local potential energy density and G(rc) is the local kinetic density evaluated at the bond critical points, rc. A calculation of the ratio for the MO bonded interactions comprising a relatively large number of molecules and earth materials, together with the constraints imposed by the values of 2?(rc) and the local electronic energy density H(rc) = G(rc) + V(rc) in the HF study, yielded the same classification for the oxides as found for the fluorides. This is true despite the different trends of the bond critical point and local energy properties with the bond length displayed by the HF and MO bonded interactions. LiO, NaO and MgO bonded interactions classify as closed shell ionic bonds, BeO, AlO, SiO, BO and PO bonded interactions classify as bonds of intermediate character and NO bonded interactions classify as shared covalent bonds. CO and SO bonded interactions classify as both intermediate and covalent bonded interactions. The CO triple bonded interaction classifies as a bond of intermediate character and the CO single bonded interaction classifies as a covalent bond whereas their H(rc) value indicates that they are both covalent bonds. The |V(rc)|/G(rc) ratios for the BeO, AlO and SiO bonded interactions indicate that they have a substantial component of ionic character despite their classification as bonds of intermediate character. The trend between |V(rc)|/G(rc) and the character of the bonded interaction is consistent with trends expected from electronegativity considerations. The connection between the net charges and the experimental SiO bond length evaluated for the Si and O atoms comprising two orthosilicates are examined in terms of the |V(rc)|/G(rc) values.

  19. The Trouble with Chemical Energy: Why Understanding Bond Energies Requires an Interdisciplinary Systems Approach

    ERIC Educational Resources Information Center

    Cooper, Melanie M.; Klymkowsky, Michael W.

    2013-01-01

    Helping students understand "chemical energy" is notoriously difficult. Many hold inconsistent ideas about what energy is, how and why it changes during the course of a chemical reaction, and how these changes are related to bond energies and reaction dynamics. There are (at least) three major sources for this problem: 1) the way biologists talk

  20. Calculation of activation energies for hydrogen-atom abstractions by radicals containing carbon triple bonds

    NASA Technical Reports Server (NTRS)

    Brown, R. L.; Laufer, A. H.

    1981-01-01

    Activation energies are calculated by the bond-energy-bond-order (BEBO) and the bond-strength-bond-length (BSBL) methods for the reactions of C2H radicals with H2, CH4, and C2H6 and for the reactions of CN radicals with H2 and CH4. The BSBL technique accurately predicts the activation energies for these reactions while the BEBO method yields energies averaging 9 kcal higher than those observed. A possible reason for the disagreement is considered.

  1. A revised set of values of single-bond radii derived from the observed interatomic distances in metals by correction for bond number and resonance energy

    PubMed Central

    Pauling, Linus; Kamb, Barclay

    1986-01-01

    An earlier discussion [Pauling, L. (1947) J. Am. Chem. Soc. 69, 542] of observed bond lengths in elemental metals with correction for bond number and resonance energy led to a set of single-bond metallic radii with values usually somewhat less than the corresponding values obtained from molecules and complex ions. A theory of resonating covalent bonds has now been developed that permits calculation of the number of resonance structures per atom and of the effective resonance energy per bond. With this refined method of correcting the observed bond lengths for the effect of resonance energy, a new set of single-bond covalent radii, in better agreement with values from molecules and complex ions, has been constructed. PMID:16593698

  2. Metallic bond effects on mean excitation energies for stopping powers

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Xu, Y. J.

    1982-01-01

    Mean excitation energies for first row metals are evaluated by means of the local plasma approximation. Particle corrections based on Pines' (1953) procedure and the Wigner Seitz (1934) model of the metallic state are included. The agreement with experimental values is remarkably good. In contrast to previous work, the calculations given here estimate shifts in the plasma frequency according to the theory for plane wave states in an extended plasma as calculated by Pines. It is demonstrated that the effects of the metallic bond in lithium and beryllium are quite large and that they appear mainly as a result of collective oscillations in the 'free' electron gas formed from the valence electrons. The usefulness of the plasma frequency shift derived for a degenerate electron gas in predicting the plasma frequency shift within the ion core is considered surprising.

  3. Cleavage of thymine N3H bonds by low-energy electrons attached Magali Theodore 1

    E-print Network

    Simons, Jack

    Cleavage of thymine N3H bonds by low-energy electrons attached to base p* orbitals Magali The. In earlier studies, we considered SSBs induced by low-energy electrons that attach to DNA bases' p* orbitals or to phosphate P@O p* orbitals to cleave sugarphosphate CO bonds or basesugar N1C bonds. We also studied

  4. / http://www.sciencemag.org/content/early/recent / 20 December 2012 / Page 1/ 10.1126/science.1231434 The many strategies for functionalizing C=C and CH bonds that have

    E-print Network

    Arnold, Frances H.

    and pharmaceuticals (5). The asymmetric cyclopropanation of olefins with high-energy carbene precursors (e carbenoid transfers, thereby combining the high levels of regio- and stereoselectivity of enzymes scope mani- fest the reactivity of the same high-valent iron-oxene intermediate, Compound I (Fig. 1

  5. Model energy landscapes and the force-induced dissociation of ligand-receptor bonds.

    PubMed Central

    Strunz, T; Oroszlan, K; Schumakovitch, I; Gntherodt, H; Hegner, M

    2000-01-01

    We discuss models for the force-induced dissociation of a ligand-receptor bond, occurring in the context of cell adhesion or single molecule unbinding force measurements. We consider a bond with a structured energy landscape which is modeled by a network of force dependent transition rates between intermediate states. The behavior of a model with only one intermediate state and a model describing a molecular zipper is studied. We calculate the bond lifetime as a function of an applied force and unbinding forces under an increasing applied load and determine the relationship between both quantities. The dissociation via an intermediate state can lead to distinct functional relations of the bond lifetime on force. One possibility is the occurrence of three force regimes where the lifetime of the bond is determined by different transitions within the energy landscape. This case can be related to recent experimental observations of the force-induced dissociation of single avidin-biotin bonds. PMID:10968985

  6. Interstellar Isomers: The Importance of Bonding Energy Differences

    NASA Technical Reports Server (NTRS)

    Remijan, Anthony J.; Hollis, J. M.; Lovas, F. J.; Plusquellic, D. F.; Jewell, P. R.

    2005-01-01

    We present strong detections of methyl cyanide (CH3CN), vinyl cyanide (CH2CHCN), ethyl cyanide (CH3CH2CN) and cyanodiacetylene (HC4CN) molecules with the Green Bank Telescope (GBT) toward the Sgr B2(N) molecular cloud. Attempts to detect the corresponding isocyanide isomers were only successful in the case of methyl isocyanide (CH3NC) for its J(sub K) = 1(sub 0) - 0(sub 0) transition, which is the first interstellar report of this line. To determine the spatial distribution of CH3NC, we used archival Berkeley-Illinois-Maryland Association (BIMA) array data for the J(sub K) = 1(sub 0) - 0(sub 0) transitions but no emission was detected. From ab initio calculations, the bonding energy difference between the cyanide and isocyanide molecules is greater than 8500 per centimeter (greater than 12,000 K). Thus, cyanides are the more stable isomers and would likely be formed more preferentially over their isocyanide counterparts. That we detect CH3NC emission with a single antenna (Gaussian beamsize(omega(sub B))=1723 arcsec(sup 2)) but not with an interferometer (omega(sub b)=192 arcsec(sup 2)), strongly suggests that CH3NC has a widespread spatial distribution toward the Sgr B2(N) region. Other investigators have shown that CH3CN is present both in the LMH hot core of Sgr B2(N) and in the surrounding medium, while we have shown that CH3NC appears to be deficient in the LMH hot core. Thus, largescale, non-thermal processes in the surrounding medium may account for the conversion of CH3CN to CH3NC while the LMH hot core, which is dominated by thermal processes, does not produce a significant amount of CH3NC. Ice analog experiments by other investigators have shown that radiation bombardment of CH3CN can produce CH3NC, thus supporting our observations. We conclude that isomers separated by such large bonding energy differences are distributed in different interstellar environments, making the evaluation of column density ratios between such isomers irrelevant unless it can be independently shown that these species are co-spatial.

  7. Palladium-catalyzed C-C, C-N and C-O bond formation

    E-print Network

    Huang, Xiaohua, 1973-

    2003-01-01

    New methods for Pd-catalyzed cross-coupling reactions of aryl halides or arenesulfonates are described. Key to the success of these transformations is the proper choice of ligand and reaction conditions. Palladium catalysts ...

  8. groupe sous groupe ACHARD MATHIEU c c1

    E-print Network

    Chatterji, Indira Lara - Le Laboratoire de Mathématiques

    groupe sous groupe ACHARD MATHIEU c c1 AL MOUSAWI SOUAAD c c2 AUVARO-GIRELLI MARY-SARA c c1 BAUDE MELISSA c c2 BONO LUCA c c1 CACHOT TONY c c2 CHAMBRET CELINE c c1 FRANCISCO RODRIGUEZ STEPHANIE c c2 GAUBERT MIKE c c2 GAUTIER DE CHARNACE CORENTIN c c1 GAZAGNAIRE EVA c c2 GHIZZONI JESSICA c c1 GUIOT

  9. Prediction of the bond lengths, vibrational frequencies, and bond dissociation energy of octahedral seaborgium hexacarbonyl, Sg(CO){sub 6}

    SciTech Connect

    Nash, C.S.; Bursten, B.E.

    1999-11-24

    The recent syntheses of several new elements (including the recent reports of elements 116 and 118), coupled with the controversy surrounding the naming of elements 104--109, have stimulated a great interest in the chemistry of the transactinide elements. This contribution addresses hypothetical hexacarbonyl complex of seaborgium (Sg, element 106), which is predicted to be a 6d-block transition element with six valence electrons, analogous to Cr, Mo, and W. The authors have previously predicted that, if it were to exist, Sg(CO){sub 6} would exhibit metal-carbonyl bonding that is very similar to that in Cr(CO){sub 6}, Mo(CO){sub 6}, and W(CO){sub 6}, and quite unlike that of the unknown valence isoelectronic actinide complex U(CO){sub 6}. This finding is in accord with the scant experimental data available for Sg. The relativistic DV-X{alpha} method used in the earlier paper facilitated the analysis of the molecular orbitals of Sg(CO){sub 6}, but did not allow for the calculation of total-energy properties, such as bond lengths and vibrational frequencies. Here the authors will use the superior methodology they have applied to other transactinide molecules to compare the bond lengths, vibrational frequencies, and CO dissociation energy of hypothetical Sg(CO){sub 6} to those of Mo(CO){sub 6} and W(CO){sub 6}.

  10. Facilitating room-temperature Suzuki coupling reaction with light: Mott-Schottky photocatalyst for C-C-coupling

    PubMed Central

    Li, Xin-Hao; Baar, Moritz; Blechert, Siegfried; Antonietti, Markus

    2013-01-01

    The Suzuki coupling reaction is one of the most practiced classes of catalytic C-C bond formation. The development of new means of activating molecules and bonds over old catalysts for C-C bond formation is a fundamental objective for chemists. Here, we report the room-temperature C-C bond formation over heterogeneous Pd catalysts by light-mediated catalyst activation. We employ stimulated electron transfer at the metal-semiconductor interface from optically active mesoporous carbon nitride nanorods to Pd nanoparticles. This photocatalytic pathway is highly efficient for coupling aryl halides with various coupling partners with high activity and selectivity under photo irradiation and very mild conditions.

  11. Bond Energy Sums in Benzene, Cyclohexatriene and Cyclohexane Prove Resonance Unnecessary

    E-print Network

    Raji Heyrovska

    2008-07-27

    The recent new structure of benzene shows that it consists of three C atoms of radii as in graphite alternating with three C atoms with double bond radii. This is different from the hypothetical cyclohexatriene (Kekule structure) involving alternate double and single bonds. It was shown that the difference in the bond energy sum of the atomic structure of benzene from that of the Kekule structure is the energy (erroneously) assumed to be due to resonance. Here it is shown that the present structure of benzene also explains the energy of hydrogenation into cyclohexane and its difference from that of cyclohexatriene.

  12. Atomistic spectrometrics of local bond-electron-energy pertaining to Na and K clusters

    NASA Astrophysics Data System (ADS)

    Bo, Maolin; Wang, Yan; Huang, Yongli; Liu, Yonghui; Li, Can; Sun, Chang Q.

    2015-01-01

    Consistency between density functional theory calculations and photoelectron spectroscopy measurements confirmed our predications on the undercoordination-induced local bond relaxation and core level shift of Na and K clusters. It is clarified that the shorter and stronger bonds between under-coordinated atoms cause local densification and local potential well depression and shift the electron binding-energy accordingly. Numerical consistency turns out the energy levels for an isolated Na (E2p = 31.167 eV) and K (E3p = 18.034 eV) atoms and their respective bulk shifts of 2.401 eV and 2.754 eV, which is beyond the scope of conventional approaches. This strategy has also resulted in quantification of the local bond length, bond energy, binding energy density, and atomic cohesive energy associated with the undercoordinated atoms.

  13. Bond Energies and Thermochemical Properties of Ring-Opened Diradicals and Carbenes of exo-Tricyclo[5.2.1.0(2,6)]decane.

    PubMed

    Hudzik, Jason M; Castillo, lvaro; Bozzelli, Joseph W

    2015-09-24

    Exo-tricyclo[5.2.1.0(2,6)]decane (TCD) or exo-tetrahydrodicyclopentadiene is an interesting strained ring compound and the single-component high-energy density hydrocarbon fuel known as JP-10. Important initial reactions of TCD at high temperatures could cleave a strained carbon-carbon (C-C) bond in the ring system creating diradicals also constrained by the remaining ring system. This study determines the thermochemical properties of these diradicals (TCD-H2 mJ-nJ where m and n correspond to the cleaved carbons sites) including the carbon-carbon bond dissociation energy (C-C BDE) corresponding to the cleaved TCD site. Thermochemical properties including enthalpies (?Hf298), entropies (S(T)), heat capacities (Cp(T)), and C-H and C-C BDEs for the parent (TCD-H2 m-n), radical (TCD-H2 mJ-n and m-nJ), diradical (TCD-H2 mJ-nJ), and carbene (TCD-H2 mJJ-n and m-nJJ) species are determined. Structures, vibrational frequencies, moments of inertia, and internal rotor potentials are calculated at the B3LYP/6-31G(d,p) level of theory. Standard enthalpies of formation in the gas phase for the TCD-H2 m-n parent and radical species are determined using the B3LYP density functional theory and the higher level G3MP2B3 and CBS-QB3 composite methods. For singlet and triplet TCD diradicals and carbenes, M06-2X, ?B97X-D, and CCSD(T) methods are included in the analysis to determine ?Hf298 values. The C-C BDEs are further calculated using CASMP2(2,2)/aug-cc-pvtz//CASSCF(2,2)/cc-pvtz and with the CASMP2 energies extrapolated to the complete basis set limit. The bond energies calculated with these methods are shown to be comparable to the other calculation methods. Isodesmic work reactions are used for enthalpy analysis of these compounds for effective cancelation of systematic errors arising from ring strain. C-C BDEs range from 77.4 to 84.6 kcal mol(-1) for TCD diradical singlet species. C-H BDEs for the parent TCD-H2 m-n carbon sites range from 93 to 101 kcal mol(-1) with a similar range seen for loss of the second hydrogen to generate the diradical singlet species. A wider range for C-C BDEs is seen for the carbenes from about 77 to 100 kcal mol(-1) as compared to the diradicals. Results from the DFT methods for the parents, radicals, diradicals, and carbenes are in good agreement with results from the composite methods using our sets of work reactions. PMID:26295335

  14. Hypovalency--a kinetic-energy density description of a 4c-2e bond.

    PubMed

    Jacobsen, Heiko

    2009-06-01

    A bond descriptor based on the kinetic energy density, the localized-orbital locator (LOL), is used to characterize the nature of the chemical bond in electron deficient multi-center bonds. The boranes B(2)H(6), B(4)H(4), B(4)H(10), [B(6)H(6)](2-), and [B(6)H(7)](-) serve as prototypical examples of hypovalent 3c-2e and 4c-2e bonding. The kinetic energy density is derived from a set of Kohn-Sham orbitals obtained from pure density functional calculations (PBE/TZVP), and the topology of LOL is analyzed in terms of (3,-3) attractors (Gamma). The B-B-B and B-H-B 3c-2e, and the B-B-H-B 4c-2e bonding situations are defined by their own characteristic LOL profiles. The presence of one attractor in relation to the three or four atoms that are engaged in electron deficient bonding provides sufficient indication of the type of 3c-2e or 4c-2e bond present. For the 4c-2e bond in [B(6)H(7)](-) the LOL analysis is compared to results from an experimental QTAIM study. PMID:19452076

  15. The effect of bond functions on dissociation energies

    NASA Technical Reports Server (NTRS)

    Bauschlicher, C. W., Jr.

    1985-01-01

    The procedure employing bond functions recently suggested by Wright and Buenker has been applied to the N2 X 1 Sigma g + potential curve within the CAS SCF + MRSD CI treatment of electron correlation. The basis set used herein is identical to that employed by these authors in their SCF + CI calculations. The De and and the shape of the resulting potential curve, as judged by the computed vibrational levels, is not so accurate as would be expected from the results reported by Wright and Buenker (1984). The results indicate that using the CI superposition errors associated with bond functions to cancel basis set incompleteness depends on the treatment of the electron correlation.

  16. Atomic Level Distributed Strain within Graphene Divacancies from Bond Rotations.

    PubMed

    Chen, Qu; Robertson, Alex W; He, Kuang; Gong, Chuncheng; Yoon, Euijoon; Lee, Gun-Do; Warner, Jamie H

    2015-08-25

    Vacancy defects play an important role in influencing the properties of graphene, and understanding their detailed atomic structure is crucial for developing accurate models to predict their impact. Divacancies (DVs) are one of the most common defects in graphene and can take three different structural forms through various sequences of bond rotations to minimize the energy. Using aberration-corrected transmission electron microscopy with monochromation of the electron source, we resolve the position of C atoms in graphene and measure the C-C bond lengths within the three DVs, enabling a map of bond strain to be generated. We show that bond rotations reduce the maximum single bond strain reached within a DV and help distribute the strain over a larger number of bonds to minimize the peak magnitude. PMID:26204434

  17. Effect of ZnO on the interfacial bonding between Na 2O-B 2O 3-SiO 2 vitrified bond and diamond

    NASA Astrophysics Data System (ADS)

    Wang, P. F.; Li, Zh. H.; Li, J.; Zhu, Y. M.

    2009-08-01

    Diamond composites were prepared by sintering diamond grains with low melting Na 2O-B 2O 3-SiO 2 vitrified bonds in air. The influence of ZnO on the wettability and flowing ability of Na 2O-B 2O 3-SiO 2 vitrified bonds was characterized by wetting angle, the interfacial bonding states between diamond grains and the vitrified bonds were observed by scanning electron microscope (SEM), and the micro-scale bonding mechanism in the interfaces was investigated by means of energy-dispersive spectrometer (EDS), Fourier transform infrared (FTIR) spectrometer and X-ray photoelectron spectroscopy (XPS). The experimental results showed that ZnO facilitated the dissociation of boron/silicon-oxygen polyhedra and the formation of larger amount of non-bridging oxygen in the glass network, which resulted in the increase of the vitrified bonds' wettability and the formation of -C dbnd O, -O-H and -C-H bonds on the surface of diamond grains. B and Si diffused from the vitrified bonds to the interface, and C-C, C-O, C dbnd O and C-B bond formed on the surface of sintered diamond grains during sintering process, by which the interfacial bonding between diamond grains and the vitrified bonds was strengthened.

  18. Comparison of the proton-transfer paths in hydrogen bonds from theoretical potential-energy surfaces and the concept of conservation of bond order III. O-H-O hydrogen bonds.

    PubMed

    Majerz, Irena; Olovsson, Ivar

    2010-01-01

    The quantum-mechanically derived reaction coordinates (QMRC) for the proton transfer in O-H-O hydrogen bonds have been derived from ab initio calculations of potential-energy surfaces. A comparison is made between the QMRC and the corresponding bond-order reaction coordinates (BORC) derived by applying the Pauling bond order concept together with the principle of conservation of bond order. In agreement with earlier results for N-H-N(+) hydrogen bonds there is virtually perfect agreement between the QMRC and BORC curves for intermolecular O-H-O hydrogen bonds. For intramolecular O-H-O hydrogen bonds, the donor and acceptor parts of the molecule impose strong constraints on the OO distance and the QMRC does not follow the BORC relation in the whole range. The neutron-determined proton positions are located close to the theoretically calculated potential-energy minima, and where the QMRC and the BORC curves coincide with each other. The results confirm the universal character of intermolecular hydrogen bonds: BORC is identical with QMRC and the proton can be moved from donor to acceptor keeping its valency equal to 1. The shape of PES for intramolecular hydrogen bonds is more complex as it is sensitive to the geometry of the molecule as well as of the hydrogen bridge. PMID:20379578

  19. Rhodium-Carbon Bond Energies in TpRh(CNneopentyl)(CH2X)H: Quantifying Stabilization Effects in M-C Bonds

    E-print Network

    Jones, William D.

    Rhodium-Carbon Bond Energies in TpRh(CNneopentyl)(CH2X)H: Quantifying Stabilization Effects in M carbonyl shows preferential formation of linear over branched aldehydes (4:1), and use of a bulkier rhodium

  20. Event anisotropy in 4.2A GeV/c C+C collisions

    E-print Network

    Lj. Simic; J. Milosevic

    2001-06-20

    The directed and elliptic flow of protons and negative pions in 4.2A GeV/c C+C collisions is studied using the Fourier analysis of azimuthal distributions. It is found that the protons exhibit pronounced directed flow, while the flow of pions is either non existent or too weak to be detected experimentally. Also, it is found that in the entire rapidity interval the elliptic flow is very small if not zero. These results are confirmed by the Quark-Gluon-String Model (QGSM) and the relativistic transport model (ART 1.0), except that these models predict very weak antiflow of pions. The more detailed comparison with the QGSM suggests that the decay of resonances and rescattering of secondaries dominantly determine the proton and negative pion flow at this energy.

  1. Hydrogen bond cooperativity in water hexamers: atomic energy perspective of local stabilities.

    PubMed

    Albrecht, Laura; Chowdhury, Saptarshi; Boyd, Russell J

    2013-10-17

    Atomic energies are used to describe local stability in eight low-lying water hexamers: prism, cage, boat 1, boat 2, bag, chair, book 1, and book 2. The energies are evaluated using the quantum theory of atoms in molecules (QTAIM) at MP2/aug-cc-pVTZ geometries. It is found that the simple, stabilizing cooperativity observed in linear hydrogen-bonded water systems is diminished as clusters move from nearly planar to three-dimensional structures. The prism, cage, and bag clusters can have local water stabilities differing up to 5 kcal mol(-1) as a result of mixed cooperative and anticooperative interactions. At the atomic level, in many cases a water may have a largely stabilized oxygen atom but the net water stability will be diminished due to strong destabilization of the water's hydrogen atoms. Analysis of bond critical point (BCP) electron densities shows that the reduced cooperativity results in a decrease in hydrogen bond strength and an increase in covalent bond strength, most evident in the prism. The chair, with the greatest cooperativity, has the largest average electron density at the BCP per hydrogen bond, whereas the cage has the largest total value for BCP density at all hydrogen bonds. The cage also has the second largest value (after the prism) for covalent bond critical point densities and an oxygen-oxygen BCP which may factor into the experimentally observed stability of the structure. PMID:24067198

  2. Protein unfolding from free-energy calculations: Integration of the Gaussian network model with bond binding energies

    NASA Astrophysics Data System (ADS)

    Srivastava, Amit; Granek, Rony

    2015-02-01

    Motivated by single molecule experiments, we study thermal unfolding pathways of four proteins, chymotrypsin inhibitor, barnase, ubiquitin, and adenylate kinase, using bond network models that combine bond energies and elasticity. The protein elasticity is described by the Gaussian network model (GNM), to which we add prescribed bond binding energies that are assigned to all (nonbackbone) connecting bonds in the GNM of native state and assumed identical for simplicity. Using exact calculation of the Helmholtz free energy for this model, we consider bond rupture single events. The bond designated for rupture is chosen by minimizing the free-energy difference for the process, over all (nonbackbone) bonds in the network. Plotting the free-energy profile along this pathway at different temperatures, we observe a few major partial unfolding, metastable or stable, states, that are separated by free-energy barriers and change role as the temperature is raised. In particular, for adenylate kinase we find three major partial unfolding states, which is consistent with single molecule FRET experiments [Pirchi et al., Nat. Commun. 2, 493 (2011), 10.1038/ncomms1504] for which hidden Markov analysis reveals between three and five such states. Such states can play a major role in enzymatic activity.

  3. Bond Graph Modeling and Validation of an Energy Regenerative System for Emulsion Pump Tests

    PubMed Central

    Li, Yilei; Zhu, Zhencai; Chen, Guoan

    2014-01-01

    The test system for emulsion pump is facing serious challenges due to its huge energy consumption and waste nowadays. To settle this energy issue, a novel energy regenerative system (ERS) for emulsion pump tests is briefly introduced at first. Modeling such an ERS of multienergy domains needs a unified and systematic approach. Bond graph modeling is well suited for this task. The bond graph model of this ERS is developed by first considering the separate components before assembling them together and so is the state-space equation. Both numerical simulation and experiments are carried out to validate the bond graph model of this ERS. Moreover the simulation and experiments results show that this ERS not only satisfies the test requirements, but also could save at least 25% of energy consumption as compared to the original test system, demonstrating that it is a promising method of energy regeneration for emulsion pump tests. PMID:24967428

  4. Bond graph modeling and validation of an energy regenerative system for emulsion pump tests.

    PubMed

    Li, Yilei; Zhu, Zhencai; Chen, Guoan

    2014-01-01

    The test system for emulsion pump is facing serious challenges due to its huge energy consumption and waste nowadays. To settle this energy issue, a novel energy regenerative system (ERS) for emulsion pump tests is briefly introduced at first. Modeling such an ERS of multienergy domains needs a unified and systematic approach. Bond graph modeling is well suited for this task. The bond graph model of this ERS is developed by first considering the separate components before assembling them together and so is the state-space equation. Both numerical simulation and experiments are carried out to validate the bond graph model of this ERS. Moreover the simulation and experiments results show that this ERS not only satisfies the test requirements, but also could save at least 25% of energy consumption as compared to the original test system, demonstrating that it is a promising method of energy regeneration for emulsion pump tests. PMID:24967428

  5. Low-Energy (0.1 eV) Electron Attachment SS Bond Cleavage

    E-print Network

    Simons, Jack

    Low-Energy (0.1 eV) Electron Attachment SS Bond Cleavage Assisted by Coulomb Stabilization the Rydberg radical H3CSSCH2CH2NH3) or into the SS antibonding * orbital is shown to be able to produce the same SS bond fragmentation products H3CS and HSCH2CH2NH2, albeit by very different pathways

  6. Chemical Bonds II

    ERIC Educational Resources Information Center

    Sanderson, R. T.

    1972-01-01

    The continuation of a paper discussing chemical bonding from a bond energy viewpoint, with a number of examples of single and multiple bonds. (Part I appeared in volume 1 number 3, pages 16-23, February 1972.) (AL)

  7. Topological properties of hydrogen bonds and covalent bonds from charge densities obtained by the maximum entropy method (MEM)

    PubMed Central

    Netzel, Jeanette; van Smaalen, Sander

    2009-01-01

    Charge densities have been determined by the Maximum Entropy Method (MEM) from the high-resolution, low-temperature (T ? 20?K) X-ray diffraction data of six different crystals of amino acids and peptides. A comparison of dynamic deformation densities of the MEM with static and dynamic deformation densities of multipole models shows that the MEM may lead to a better description of the electron density in hydrogen bonds in cases where the multipole model has been restricted to isotropic displacement parameters and low-order multipoles (l max = 1) for the H atoms. Topological properties at bond critical points (BCPs) are found to depend systematically on the bond length, but with different functions for covalent CC, CN and CO bonds, and for hydrogen bonds together with covalent CH and NH bonds. Similar dependencies are known for AIM properties derived from static multipole densities. The ratio of potential and kinetic energy densities |V(BCP)|/G(BCP) is successfully used for a classification of hydrogen bonds according to their distance d(H?O) between the H atom and the acceptor atom. The classification based on MEM densities coincides with the usual classification of hydrogen bonds as strong, intermediate and weak [Jeffrey (1997) ?. An Introduction to Hydrogen Bonding. Oxford University Press]. MEM and procrystal densities lead to similar values of the densities at the BCPs of hydrogen bonds, but differences are shown to prevail, such that it is found that only the true charge density, represented by MEM densities, the multipole model or some other method can lead to the correct characterization of chemical bonding. Our results do not confirm suggestions in the literature that the promolecule density might be sufficient for a characterization of hydrogen bonds. PMID:19767685

  8. Analysis of a compressed thin film bonded to a compliant substrate: the energy scaling law

    E-print Network

    patterns, determining for each the associated scaling law. The one with the best law was a periodic "MiuraAnalysis of a compressed thin film bonded to a compliant substrate: the energy scaling law Robert V law of the minimum energy with respect to the physical parameters of the problem, and we prove

  9. Hydrogen bonding induced enhancement of Fermi resonances: ultrafast vibrational energy flow dynamics in aniline-d?.

    PubMed

    Costard, Rene; Greve, Christian; Fidder, Henk; Nibbering, Erik T J

    2015-02-12

    With hydrogen bonding of the amino group of aniline-d5 we can identify the roles of Fermi enhanced combination and overtone states in intramolecular vibrational re-distribution (IVR) pathways for N-H stretching excitations. Using linear Fourier transform infrared (FT-IR) spectroscopy, ultrafast one- and two-color IR-pump-IR-probe spectroscopy, and femtosecond two-dimensional IR spectroscopy, we can identify the primary accepting modes for N-H stretching excitations. In particular, a key role is played by the ?(NH2) bending degree of freedom, either via its ? = 2 overtone state or via a combination state with the ?(C?C) ring stretching mode. No significant transient population in these Fermi enhanced combination/overtone states can be observed, a consequence of similar decay rates of these Fermi enhanced combination/overtone states and of the N-H stretching states. A similar magnitude of the transient response of the two fingerprint modes regardless of direct excitation of the Fermi enhanced combination/overtone levels or of the N-H stretching states suggests an underlying coupling mechanism facilitating common IVR pathways. This mechanism is expected to be of general importance for other organic compounds with hydrogen-bonded amino groups, including DNA bases. PMID:25393885

  10. Phonon-energy-coupling enhancement: Strengthening the chemical bonds of the SiO2/Si system

    E-print Network

    Chen, Zhi

    Phonon-energy-coupling enhancement: Strengthening the chemical bonds of the SiO2/Si system Zhi and Engineering, University of Kentucky, Lexington, Kentucky 40506 Fuqian Yang Department of Chemical-energy-coupling enhancement. The vibrational modes of the SiSi and SiO bonds exhibit enhanced energy coupling when the rapid

  11. The Dissociation Energies of He2, HeH, and ArH; A Bond Function Study

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry; Arnold, James (Technical Monitor)

    1998-01-01

    The bond energies and bond lengths are determined for He2, HeH, and ArH at the CCSD(T) level using both atom-centered basis sets and those that include bond functions. The addition of bond functions dramatically improves the rate of convergence of the results with respect to the size of the atom-centered basis set; with bond functions, triple zeta atom-centered basis set, outperform quintuple zeta basis sets without bond functions. The addition of bond functions also reduces the number of diffuse functions that must be added to the atom-centered sets. Employing bond functions appear to offer a very cost effective method of computing the interaction between weakly bound systems, especially for He.

  12. Exotic c c-bar Mesons

    E-print Network

    Eric Braaten

    2008-08-21

    A surprising number of new c c-bar mesons with masses above the D D-bar threshold have been discovered at the B factories. Some of them are ordinary charmonium states, but others are definitely exotic mesons. The current theoretical status of the new c c-bar mesons is summarized.

  13. Comparison of the proton-transfer path in hydrogen bonds from theoretical potential-energy surfaces and the concept of conservation of bond order. II. (N-H...N)(+) hydrogen bonds.

    PubMed

    Majerz, Irena; Olovsson, Ivar

    2007-08-01

    The quantum-mechanically derived reaction coordinates (QMRC) for the proton transfer in (N-H-N)(+) hydrogen bonds have been derived from ab initio calculations of potential-energy surfaces. A comparison is made between the QMRC and the corresponding bond-order reaction coordinates (BORC) derived by applying the Pauling bond-order concept together with the principle of conservation of bond order. We find virtually perfect agreement between the QMRC and the BORC for intermolecular (N-H-N)(+) hydrogen bonds. In contrast, for intramolecular (N-H-N)(+) hydrogen bonds, the donor and acceptor parts of the molecule impose strong constraints on the N-N distance and the QMRC does not follow the BORC relation in the whole range. The X-ray determined hydrogen positions are not located exactly at the theoretically calculated potential-energy minima, but instead at the point where the QMRC and the BORC coincide with each other. On the other hand, the optimized hydrogen positions, with other atoms in the cation fixed as in the crystal structure, are closer to these energy minima. Inclusion of the closest neighbours in the theoretical calculations has a rather small effect on the optimized hydrogen positions. [Part I: Olovsson (2006). Z. Phys. Chem. 220, 797-810.]. PMID:17641436

  14. 99. Catalog HHistory 1, C.C.C., 23 Guard Rail Construction, Negative ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    99. Catalog H-History 1, C.C.C., 23 Guard Rail Construction, Negative No. P455e (Photographer and date unknown) GUARD RAIL INSTALLATION. - Skyline Drive, From Front Royal, VA to Rockfish Gap, VA , Luray, Page County, VA

  15. 98. Catalog HHistory 1, C.C.C., 19 Tree Planting, Negative No. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    98. Catalog H-History 1, C.C.C., 19 Tree Planting, Negative No. P 474c (Photographer and date unknown) TRANSPLANTING TREE. - Skyline Drive, From Front Royal, VA to Rockfish Gap, VA , Luray, Page County, VA

  16. 100. Catalog HHistory 1, C.C.C., 34 Landscaping, Negative No. P ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    100. Catalog H-History 1, C.C.C., 34 Landscaping, Negative No. P 733c (Photographer and date unknown) SLOPE MAINTENANCE WORK BY CCC. - Skyline Drive, From Front Royal, VA to Rockfish Gap, VA , Luray, Page County, VA

  17. 101. Catalog HHistory 1, C.C.C., 34 Landscaping, Negative No. 1340 ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    101. Catalog H-History 1, C.C.C., 34 Landscaping, Negative No. 1340 (Photographer and date unknown) BANK BLENDING WORK BY CCC. - Skyline Drive, From Front Royal, VA to Rockfish Gap, VA , Luray, Page County, VA

  18. Facile C(sp(2))-C(sp(2)) bond cleavage in oxalic acid-derived radicals.

    PubMed

    Molt, Robert W; Lecher, Alison M; Clark, Timothy; Bartlett, Rodney J; Richards, Nigel G J

    2015-03-11

    Oxalate decarboxylase (OxDC) catalyzes the Mn-dependent conversion of the oxalate monoanion into CO2 and formate. Many questions remain about the catalytic mechanism of OxDC although it has been proposed that the reaction proceeds via substrate-based radical intermediates. Using coupled cluster theory combined with implicit solvation models we have examined the effects of radical formation on the structure and reactivity of oxalic acid-derived radicals in aqueous solution. Our results show that the calculated solution-phase free-energy barrier for C-C bond cleavage to form CO2 is decreased from 34.2 kcal/mol for oxalic acid to only 9.3 kcal/mol and a maximum of 3.5 kcal/mol for the cationic and neutral oxalic acid-derived radicals, respectively. These studies also show that the C-C ? bonding orbital of the radical cation contains only a single electron, giving rise to an elongated C-C bond distance of 1.7 ; a similar lengthening of the C-C bond is not observed for the neutral radical. This study provides new chemical insights into the structure and stability of plausible intermediates in the catalytic mechanism of OxDC, and suggests that removal of an electron to form a radical (with or without the concomitant loss of a proton) may be a general strategy for cleaving the unreactive C-C bonds between adjacent sp(2)-hybridized carbon atoms. PMID:25702589

  19. Average bond energies between boron and elements of the fourth, fifth, sixth, and seventh groups of the periodic table

    NASA Technical Reports Server (NTRS)

    Altshuller, Aubrey P

    1955-01-01

    The average bond energies D(gm)(B-Z) for boron-containing molecules have been calculated by the Pauling geometric-mean equation. These calculated bond energies are compared with the average bond energies D(exp)(B-Z) obtained from experimental data. The higher values of D(exp)(B-Z) in comparison with D(gm)(B-Z) when Z is an element in the fifth, sixth, or seventh periodic group may be attributed to resonance stabilization or double-bond character.

  20. Chemical bond as a test of density-gradient expansions for kinetic and exchange energies

    SciTech Connect

    Perdew, J.P.; Levy, M.; Painter, G.S.; Wei, S.; Lagowski, J.B.

    1988-01-15

    Errors in kinetic and exchange contributions to the molecular bonding energy are assessed for approximate density functionals by reference to near-exact Hartree-Fock values. From the molecular calculations of Allan et al. and of Lee and Ghosh, it is demonstrated that the density-gradient expansion does not accurately describe the noninteracting kinetic contribution to the bonding energy, even when this expansion is carried to fourth order and applied in its spin-density-functional form to accurate Hartree-Fock densities. In a related study, it is demonstrated that the overbinding of molecules such as N/sub 2/ and F/sub 2/, which occurs in the local-spin-density (LSD) approximation for the exchange-correlation energy, is not attributable to errors in the self-consistent LSD densities. Contrary to expectations based upon the Gunnarsson-Jones nodality argument, it is found that the LSD approximation for the exchange energy can seriously overbind a molecule even when bonding does not create additional nodes in the occupied valence orbitals. LSD and exact values for the exchange contribution to the bonding energy are displayed and discussed for several molecules.

  1. A periodic energy decomposition analysis method for the investigation of chemical bonding in extended systems

    SciTech Connect

    Raupach, Marc; Tonner, Ralf

    2015-05-21

    The development and first applications of a new periodic energy decomposition analysis (pEDA) scheme for extended systems based on the Kohn-Sham approach to density functional theory are described. The pEDA decomposes the bonding energy between two fragments (e.g., the adsorption energy of a molecule on a surface) into several well-defined terms: preparation, electrostatic, Pauli repulsion, and orbital relaxation energies. This is complemented by consideration of dispersion interactions via a pairwise scheme. One major extension toward a previous implementation [Philipsen and Baerends, J. Phys. Chem. B 110, 12470 (2006)] lies in the separate discussion of electrostatic and Pauli and the addition of a dispersion term. The pEDA presented here for an implementation based on atomic orbitals can handle restricted and unrestricted fragments for 0D to 3D systems considering periodic boundary conditions with and without the determination of fragment occupations. For the latter case, reciprocal space sampling is enabled. The new method gives comparable results to established schemes for molecular systems and shows good convergence with respect to the basis set (TZ2P), the integration accuracy, and k-space sampling. Four typical bonding scenarios for surface-adsorbate complexes were chosen to highlight the performance of the method representing insulating (CO on MgO(001)), metallic (H{sub 2} on M(001), M = Pd, Cu), and semiconducting (CO and C{sub 2}H{sub 2} on Si(001)) substrates. These examples cover diverse substrates as well as bonding scenarios ranging from weakly interacting to covalent (shared electron and donor acceptor) bonding. The results presented lend confidence that the pEDA will be a powerful tool for the analysis of surface-adsorbate bonding in the future, enabling the transfer of concepts like ionic and covalent bonding, donor-acceptor interaction, steric repulsion, and others to extended systems.

  2. An Experimental and Theoretical Study on the Ionization Energies of Polyynes (H-(C = C)n-H; n = 1 - 9)

    SciTech Connect

    Kaiser, Ralf I.; Sun, Bian Jian; Lin, Hong Mao; Chang, Agnes H. H.; Mebel, Alexander M.; Kostko, Oleg; Ahmed, Musahid

    2010-05-17

    We present a combined experimental and theoretical work on the ionization energies of polyacetylene -- organic molecules considered as important building blocks to form polycyclic aromatic hydrocarbons (PAHs) in the proto planetary nebulae such as of CRL 618. This set of astrophysical data can be utilized with significant confidence in future astrochemical models of photon-dominated regions and also of the proto planetary nebulae CRL 618. We recommend ionization energies of polyacetylenes from diacetylene up to heptaacetylene with an experimental accuracy of +- 0.05 eV: 10.03 eV (diacetylene), 9.45 eV (triacetylene), 9.08 eV (tetraacetylene), 8.75 eV (pentaacetylene), 8.65 eV (hexaacetylene), and 8.50 eV (heptaacetylene); further, ionization energies and with an accuracy of +- 0.1 eV: 8.32 eV (octaacetylene) and 8.24 eV (nonaacetylene) were computed. Implications of these energies to the redox chemistry involved in the multiply charged metal-ion mediated chemistry of hydrocarbon-rich atmospheres of planets and their moons such as Titan are also discussed.

  3. Asymmetric hydrogen bonds in a centrosymmetric environment. III. Quantum mechanical calculations of the potential-energy surfaces for the very short hydrogen bonds in potassium hydrogen dichloromaleate.

    PubMed

    Majerz, I; Olovsson, I

    2007-10-01

    In the crystal structure of potassium hydrogen dichloromaleate there are two short hydrogen bonds of 2.44 A. The 'heavy-atom' structure is centrosymmetric (space group P1) with centers of symmetry in the middle of the O-O bonds, suggesting centered hydrogen bonds. However, earlier unconventional types of refinements of the extensive neutron data taken at 30, 90, 135, 170 and 295 K demonstrated that the H atoms are actually non-centered in the hydrogen bonds, although the environment is centrosymmetric. Traditionally it has been assumed that the hydrogen distribution adopts the same symmetry as the environment. Reviewing these unusual results it was considered of great interest to verify that the non-centered locations of the H atoms are reasonable from an energy point of view. Quantum mechanical calculations have now been carried out for the potential-energy surfaces (PES) for both the centered and non-centered locations of the H atoms. In all cases the non-centered positions are closer to the energy minima in the PES than the centered positions, and this result confirms that the structure is best described with non-centered H atoms. There is virtually perfect agreement between the quantum-mechanically derived reaction coordinates (QMRC) and the bond-order reaction coordinates (BORC) derived using Pauling's bond-order concept together with the principle of conservation of bond order. [Part I: Olovsson et al. (2001). Acta Cryst. B57, 311-316; Part II: Olovsson et al. (2002). Acta Cryst. B58, 627-631.]. PMID:17873444

  4. Which Ab Initio Wave Function Methods Are Adequate for Quantitative Calculations of the Energies of Biradicals? The Performance of Coupled-Cluster and Multi-Reference Methods Along a Single-Bond Dissociation Coordinate

    SciTech Connect

    Yang, Ke; Jalan, Amrit; Green, William H.; Truhlar, Donald G.

    2013-01-08

    We examine the accuracy of single-reference and multireference correlated wave function methods for predicting accurate energies and potential energy curves of biradicals. The biradicals considered are intermediate species along the bond dissociation coordinates for breaking the F?F bond in F2, the O?O bond in H2O2, and the C?C bond in CH3CH3. We apply a host of single-reference and multireference approximations in a consistent way to the same cases to provide a better assessment of their relative accuracies than was previously possible. The most accurate method studied is coupled cluster theory with all connected excitations through quadruples, CCSDTQ. Without explicit quadruple excitations, the most accurate potential energy curves are obtained by the single-reference RCCSDt method, followed, in order of decreasing accuracy, by UCCSDT, RCCSDT, UCCSDt, seven multireference methods, including perturbation theory, configuration interaction, and coupled-cluster methods (with MRCI+Q being the best and Mk-MR-CCSD the least accurate), four CCSD(T) methods, and then CCSD.

  5. A second-generation reactive empirical bond order (REBO) potential energy expression for hydrocarbons

    E-print Network

    Zhigilei, Leonid V.

    for hydrocarbons This article has been downloaded from IOPscience. Please scroll down to see the full text article-generation reactive empirical bond order (REBO) potential energy expression for hydrocarbons Donald W Brenner1 , Olga, lengths, and force constants for hydrocarbon molecules, as well as elastic properties, interstitial defect

  6. Condensed Lecture Notes, Part 2 Bond energy of NaCl

    E-print Network

    6 Condensed Lecture Notes, Part 2 Bond energy of NaCl If NaCl were diatomic molecule of the type Na that satisfy the octet (duplet) rule. If multiple structures are ok, then the rule of thumb is that the lowest, not OFF. 7. If there are multiple equivalent structures which satisfy the octet rule, then we say

  7. Contributions of mass and bond energy difference and interface defects on thermal boundary conductance

    NASA Astrophysics Data System (ADS)

    Choi, ChangJin; Roberts, Nicholas

    2015-09-01

    The impact of mass and bond energy difference and interface defects on thermal boundary conductance (TBC) is investigated using non-equilibrium molecular dynamics (NEMD) with the Lennard-Jones (L-J) interatomic potential. Results show that the maximum TBC is achieved when the mass and bond energy of two dissimilar materials are matched, although the effective thermal conductivity is not necessarily a maximum due to the contributions of the thermal conductivity of the constituent materials. Mass and bond energy differences result in a mismatch between phonon dispersions, limiting high frequency phonon transport at the interface. This frequency mismatch is defined by a frequency ratio, which is a ratio of the characteristic frequencies of the two materials, presented in the discussion section, and is a reference of the level of phonon dispersion mismatch. Inelastic scattering may result at higher temperatures, especially when there exists a bond energy difference, resulting in strain in the lattice, which would allow phonons outside the allowable frequency range to contribute to transport. TBC decreases abruptly with small mass differences, but at which point larger differences in mass have no impact. In addition, interdiffusion across the interface further reduces the TBC between the frequency ratios of 0.79 and 1.26 while vacancies have negligible impact.

  8. Ionic bond effects on the mean excitation energy for stopping power

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Chang, C. K.; Kamaratos, E.; Xu, Y. J.

    1982-01-01

    Molecular mean excitation energies for ionic bonded molecules calculated according to the local plasma approximation are compared to the Bragg rule. Adjustments of 15% are calculated for LiF in agreement with experiments while 6% adjustments are predicted for HF and 3% for LiH.

  9. Bonding Motifs of Noble-Gas Compounds As Described by the Local Electron Energy Density.

    PubMed

    Borocci, Stefano; Giordani, Maria; Grandinetti, Felice

    2015-06-18

    The bonding situation of some exemplary noble-gas (Ng) compounds, including HNg(+), HNgF, FNgO(-), Ng-HF, and NgBeO (Ng = He-Xe) was assayed by examining their local electron energy density H(r). In general, this function partitions the space of atomic species (neutral and ionic) into inner regions of negative values and outer regions of positive values. In the formation of chemical bonds, these atomic regions combine so to form a molecular H(r), Hmol(r), whose plotted form naturally shows the "covalent" and "noncovalent" regions of the molecular species and allows also the recognition of different types of noncovalent interactions such van der Waals, hydrogen, and ionic or partially ionic bonds. The qualitative assignment of the various bonding motifs is corroborated by the topological analysis of Hmol(r), which typically includes several critical points of rank 3 and variable signature. These points are, in particular, characterized here in terms of their bond degree (BD). From a previous definition (Espinosa J. Chem. Phys. 2002, 117, 5529-5542), this quantity is taken as the ratio between the energy density calculated at the critical point of H(r), H(rc), and the corresponding electron density ?(rc): BD = -H(rc)/?(rc). Thus, the BD is positive for covalent interactions (H(rc) < 0) and negative for noncovalent interactions (H(rc) > 0). For structurally related species, the BD result, in general, positively correlated with the binding energies and is, therefore, a semiquantitative index of stability. The present study suggests the general validity of the Hmol(r) to effectively assay the bonding motifs of noble-gas compounds. PMID:25988571

  10. Oxygen-oxygen bonds : catalytic redox pathways in energy storage

    E-print Network

    Fried, Stephen D. (Stephen David), 1987-

    2009-01-01

    Introduction: The present understanding of energy - its many forms, and its governing role in the time evolution of physical systems - underlies many of the most fundamental and unifying principles furnished by scientific ...

  11. The Scalar Relativistic Contribution to Ga-Halide Bond Energies

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Arnold, James O. (Technical Monitor)

    1998-01-01

    The one-electron Douglas Kroll (DK) and perturbation theory (+R) approaches are used to compute the scalar relativistic contribution to the atomization energies of GaFn. These results are compared with the previous GaCln results. While the +R and DK results agree well for the GaCln atom nation energies, they differ for GaFn. The present work suggests that the DK approach is more accurate than the +R approach. In addition, the DK approach is less sensitive to the choice of basis set. The computed atomization energies of GaF2 and GaF3 are smaller than the somewhat uncertain experiments. It is suggested that additional calibration calculations for the scalar relativistic effects in GaF2 and GaF3 would be valuable.

  12. The bond energy of Rh2 Jon D. Langenberg and Michael D. Morse

    E-print Network

    Morse, Michael D.

    The bond energy of Rh2 Jon D. Langenberg and Michael D. Morse Department of Chemistry, University In a spectroscopic investigation of jet-cooled Rh2 by the resonant two-photon ionization method, an abrupt energy of Rh2 is assigned as D0 Rh2 19 405 4 cm 1 2.4059 0.0005 eV. This value is compared to the results

  13. Electronic structure, molecular bonding and potential energy surfaces

    SciTech Connect

    Ruedenberg, K.

    1993-12-01

    By virtue of the universal validity of the generalized Born-Oppenheimer separation, potential energy surfaces (PES`) represent the central conceptual as well as quantitative entities of chemical physics and provide the basis for the understanding of most physicochemical phenomena in many diverse fields. The research in this group deals with the elucidation of general properties of PES` as well as with the quantitative determination of PES` for concrete systems, in particular pertaining to reactions involving carbon, oxygen, nitrogen and hydrogen molecules.

  14. Tubulin Bond Energies and Microtubule Biomechanics Determined from Nanoindentation in Silico

    PubMed Central

    2015-01-01

    Microtubules, the primary components of the chromosome segregation machinery, are stabilized by longitudinal and lateral noncovalent bonds between the tubulin subunits. However, the thermodynamics of these bonds and the microtubule physicochemical properties are poorly understood. Here, we explore the biomechanics of microtubule polymers using multiscale computational modeling and nanoindentations in silico of a contiguous microtubule fragment. A close match between the simulated and experimental forcedeformation spectra enabled us to correlate the microtubule biomechanics with dynamic structural transitions at the nanoscale. Our mechanical testing revealed that the compressed MT behaves as a system of rigid elements interconnected through a network of lateral and longitudinal elastic bonds. The initial regime of continuous elastic deformation of the microtubule is followed by the transition regime, during which the microtubule lattice undergoes discrete structural changes, which include first the reversible dissociation of lateral bonds followed by irreversible dissociation of the longitudinal bonds. We have determined the free energies of dissociation of the lateral (6.9 0.4 kcal/mol) and longitudinal (14.9 1.5 kcal/mol) tubulintubulin bonds. These values in conjunction with the large flexural rigidity of tubulin protofilaments obtained (18,00026,000 pNnm2) support the idea that the disassembling microtubule is capable of generating a large mechanical force to move chromosomes during cell division. Our computational modeling offers a comprehensive quantitative platform to link molecular tubulin characteristics with the physiological behavior of microtubules. The developed in silico nanoindentation method provides a powerful tool for the exploration of biomechanical properties of other cytoskeletal and multiprotein assemblies. PMID:25389565

  15. Quantum dynamics study of fulvene double bond photoisomerization: The role of intramolecular vibrational energy redistribution and excitation energy

    SciTech Connect

    Blancafort, Lluis; Gatti, Fabien; Meyer, Hans-Dieter

    2011-10-07

    The double bond photoisomerization of fulvene has been studied with quantum dynamics calculations using the multi-configuration time-dependent Hartree method. Fulvene is a test case to develop optical control strategies based on the knowledge of the excited state decay mechanism. The decay takes place on a time scale of several hundred femtoseconds, and the potential energy surface is centered around a conical intersection seam between the ground and excited state. The competition between unreactive decay and photoisomerization depends on the region of the seam accessed during the decay. The dynamics are carried out on a four-dimensional model surface, parametrized from complete active space self-consistent field calculations, that captures the main features of the seam (energy and locus of the seam and associated branching space vectors). Wave packet propagations initiated by single laser pulses of 5-25 fs duration and 1.85-4 eV excitation energy show the principal characteristics of the first 150 fs of the photodynamics. Initially, the excitation energy is transferred to a bond stretching mode that leads the wave packet to the seam, inducing the regeneration of the reactant. The photoisomerization starts after the vibrational energy has flowed from the bond stretching to the torsional mode. In our propagations, intramolecular energy redistribution (IVR) is accelerated for higher excess energies along the bond stretch mode. Thus, the competition between unreactive decay and isomerization depends on the rate of IVR between the bond stretch and torsion coordinates, which in turn depends on the excitation energy. These results set the ground for the development of future optical control strategies.

  16. Bond ionicity, lattice energy, bond energy and microwave dielectric properties of ZnZr(Nb1-xAx)2O8 (A = Ta, Sb) ceramics.

    PubMed

    Zhang, Ping; Zhao, Yonggui; Haitao, Wu

    2015-10-14

    The dependence of microwave dielectric properties on the structural characteristics of ZnZr(Nb1-xAx)2O8 (A = Ta, Sb) (0 ?x? 0.10) ceramics is investigated. All the compounds were prepared by a conventional solid-state reaction method and analyzed via multiphase structure refinement. The diffraction patterns of ZnZr(Nb1-xAx)2O8 (A = Ta, Sb) show the monoclinic wolframite structure of ZrZrNb2O8 which consists of an oxygen octahedron, with the Nb ion in the center of the oxygen octahedron. For the ZnZr(Nb1-xAx)2O8 (A = Ta, Sb) ceramics, the dielectric constant (?r) decreased with the decrease in Nb-site bond ionicity. The quality factor (Qf) of ZnZr(Nb1-xSbx)2O8 ceramics was found to be the highest (89?400 GHz), which is explained in terms of the average of the Nb-site lattice energy. With the decrease in the bond energy of the Nb-site, the temperature coefficient of resonant frequency (|?f|) value increased. The substitution of A(5+) (A = Ta, Sb) for Nb(5+) effectively influences the microstructure and microwave dielectric properties of ZrZrNb2O8 ceramics. PMID:26348992

  17. 2590 J. Am. Chem. SOC.1995,117, 2590-2599 The C-H Bond Energy of Benzene

    E-print Network

    Ellison, Barney

    2590 J. Am. Chem. SOC.1995,117, 2590-2599 The C-H Bond Energy of Benzene Gustavo E. Davico ion with benzene and phenide ion with ammonia: c&6 +NH2- C6H5- +NH3. The ratio of these rate constants for derived. The enthalpy of deprotonationof benzene, the C-H bond dissociationenergy, and the electron

  18. Electronic structure, stacking energy, partial charge, and hydrogen bonding in four periodic B-DNA models

    NASA Astrophysics Data System (ADS)

    Poudel, Lokendra; Rulis, Paul; Liang, Lei; Ching, W. Y.

    2014-08-01

    We present a theoretical study of the electronic structure of four periodic B-DNA models labeled (AT)10,(GC)10, (AT)5(GC)5, and (AT-GC)5 where A denotes adenine, T denotes thymine, G denotes guanine, and C denotes cytosine. Each model has ten base pairs with Na counterions to neutralize the negative phosphate group in the backbone. The (AT)5(GC)5 and (AT-GC)5 models contain two and five AT-GC bilayers, respectively. When compared against the average of the two pure models, we estimate the AT-GC bilayer interaction energy to be 19.015 Kcal/mol, which is comparable to the hydrogen bonding energy between base pairs obtained from the literature. Our investigation shows that the stacking of base pairs plays a vital role in the electronic structure, relative stability, bonding, and distribution of partial charges in the DNA models. All four models show a highest occupied molecular orbital (HOMO) to lowest unoccupied molecular orbital (LUMO) gap ranging from 2.14 to 3.12 eV with HOMO states residing on the PO4 + Na functional group and LUMO states originating from the bases. Our calculation implies that the electrical conductance of a DNA molecule should increase with increased base-pair mixing. Interatomic bonding effects in these models are investigated in detail by analyzing the distributions of the calculated bond order values for every pair of atoms in the four models including hydrogen bonding. The counterions significantly affect the gap width, the conductivity, and the distribution of partial charge on the DNA backbone. We also evaluate quantitatively the surface partial charge density on each functional group of the DNA models.

  19. Theoretical study of the C-H bond dissociation energy of C2H

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.

    1990-01-01

    A theoretical study of the convergence of the C-H bond dissociation energy D(0) in C2H with respect to both the one- and n-particle spaces is presented. The calculated C-H bond energies of C2H2 and C2H4, which are in excellent agreement with experiment, are used for calibration. The best estimate for D(0) of 112.4 + or - 2.0 kcal/mol is slightly below the recent experimental value of 116.3 + or - 2.6 kcal/mol, but substantially above a previous theoretical estimate of 102 kcal/mol. The remaining discrepancy with experiment may reflect primarily the uncertainty in the experimental D(0) value of C2 required in the analysis.

  20. Using Qualified Energy Conservation Bonds for Public Building Upgrades. Reducing Energy Bills in the City of Philadelphia

    SciTech Connect

    Zimring, Mark

    2012-07-18

    Qualified Energy Conservation Bonds (QECBs) are federally-subsidized bonds that enable state, tribal, and local government issuers to borrow money to fund a range of energy conservation projects, including public building upgrades that reduce energy use by at least 20 percent, at very attractive borrowing rates and long terms. As part of the American Recovery and Reinvestment Act (ARRA), the City of Philadelphia received a $15 million QECB award from the U.S. Department of the Treasury (Treasury). The city leveraged $6.25 million of its QECB allocation to finance half of a $12.6 million initiative to upgrade the energy efficiency of City buildings. The upgrades to four city facilities are expected to deliver over $10 million of net savings, and are a major step towards achieving the citys goal of reducing government energy consumption by 30 percent by 2015.

  1. Mapping the Globe with C & C Technologies

    NASA Astrophysics Data System (ADS)

    Kleiner, A. A.

    2001-12-01

    C & C Technologies is an international survey and mapping company with an entrepreneurial spirit that is evident throughout. C & C was recently awarded the MTS (Marine Technology Society) ROV Committee Corporate Excellence Award in recognition of their pioneering spirit displayed by the introduction of the HUGIN 3000 Autonomous Underwater Vehicle (AUV) to the offshore industry. This presentation will outline the wide variety of global mapping projects that C & C has performed for government, private sector, and academia. These include high-resolution mapping of Cater Lake, the Panama Canal, Antarctica, Lake Tahoe, and the HUGIN 3000? discovery of the German submarine U-166 in 5000 feet of water in the Gulf of Mexico. Adacemic disciplines required to support these technical challenges will be characterized and job opportunities in this emerging field will be addressed.

  2. Bond-Specific Dissociation Following Excitation Energy Transfer for Distance Constraint Determination in the Gas Phase

    PubMed Central

    2015-01-01

    Herein, we report chemistry that enables excitation energy transfer (EET) to be accurately measured via action spectroscopy on gaseous ions in an ion trap. It is demonstrated that EET between tryptophan or tyrosine and a disulfide bond leads to excited state, homolytic fragmentation of the disulfide bond. This phenomenon exhibits a tight distance dependence, which is consistent with Dexter exchange transfer. The extent of fragmentation of the disulfide bond can be used to determine the distance between the chromophore and disulfide bond. The chemistry is well suited for the examination of protein structure in the gas phase because native amino acids can serve as the donor/acceptor moieties. Furthermore, both tyrosine and tryptophan exhibit unique action spectra, meaning that the identity of the donating chromophore can be easily determined in addition to the distance between donor/acceptor. Application of the method to the Trpcage miniprotein reveals distance constraints that are consistent with a native-like fold for the +2 charge state in the gas phase. This structure is stabilized by several salt bridges, which have also been observed to be important previously in proteins that retain native-like structures in the gas phase. The ability of this method to measure specific distance constraints, potentially at numerous positions if combined with site-directed mutagenesis, significantly enhances our ability to examine protein structure in the gas phase. PMID:25174489

  3. Theoretical study of the C-H bond dissociation energy of acetylene

    NASA Technical Reports Server (NTRS)

    Taylor, Peter R.; Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.

    1990-01-01

    The authors present a theoretical study of the convergence of the C-H bond dissociation energy (D sub o) of acetylene with respect to both the one- and n-particle spaces. Their best estimate for D sub o of 130.1 plus or minus 1.0 kcal/mole is slightly below previous theoretical estimates, but substantially above the value determined using Stark anticrossing spectroscopy that is asserted to be an upper bound.

  4. Shock-induced initiation and energy release behavior of polymer bonded explosive materials

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Cai, Xuanming; Hypervelocity Impact Research Center Team

    2015-06-01

    In this paper, an initially sealed vented test chamber and a test projectile with a recessed hole were designed to complete the experiments. As the initiation takes place on the interior, great amounts of thermo-chemical energy gases were vented through a hole formed by the penetration process. The gas pressure inside the chamber was used to evaluate the energy release behavior of polymer bonded explosive materials. The impact pressure of the projectile was measured by the PVDF sensors. Based on the earlier work that the constitutive equation of polymer bonded explosive materials was established, the impact pressure of the projectile was obtained through the numerical simulation. The experimental results reveal that the impact pressure is significant to the energy release behavior, and in some extent the gas pressure improves with the velocity of the projectile. The impact pressure obtained by the experiments is comparing with which obtained through the numerical simulation, and the results of the comparing is that the value of them are closely relative. The experimental results also indicate that the constitutive equation of polymer bonded explosive materials used in the numerical simulation can correctly describe the mechanical behavior of PBX materials.

  5. 104. Catalog HHistory 1, C.C.C., 73 Picnic Furniture Construction, Negative ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    104. Catalog H-History 1, C.C.C., 73 Picnic Furniture Construction, Negative No. 8821 ca. 1936 WOOD UTILIZATION. COMPLETED RUSTIC BENCH MADE BY CCC ENROLLEES AT CAMP NP-3 FOR USE AT PARKING OVERLOOKS AND PICNIC GROUNDS. NOTE SAW IN BACKGROUND USED FOR HALVING CHESTNUT. - Skyline Drive, From Front Royal, VA to Rockfish Gap, VA , Luray, Page County, VA

  6. 102. Catalog HHistory 1, C.C.C., 34 Landscaping, Negative No. 6040a ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    102. Catalog H-History 1, C.C.C., 34 Landscaping, Negative No. 6040a (Photographer and date unknown) BEAUTIFICATION PROGRAM STARTED AS SOON AS GRADING ALONG THE DRIVE WAS COMPLETED. CCC CAMP 3 SHOWN PLANTING LAUREL. - Skyline Drive, From Front Royal, VA to Rockfish Gap, VA , Luray, Page County, VA

  7. 103. Catalog HHistory 1, C.C.C., 58 Landscaping, Negative No. 870 ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    103. Catalog H-History 1, C.C.C., 58 Landscaping, Negative No. 870 10 ca. 1936 PROPAGATION AND PLANTING. ROOTED PLANTS TRANSPLANTED FROM HOT BEDS TO CANS TO SHADED BEDS IN PREPARATION FOR PLANTING ON ROAD SLOPES. NURSERY AT NORTH ENTRANCE. - Skyline Drive, From Front Royal, VA to Rockfish Gap, VA , Luray, Page County, VA

  8. Luminescent Iridium(III) Complexes Supported by N-Heterocyclic Carbene-based C^C^C-Pincer Ligands and Aromatic Diimines

    PubMed Central

    Chung, Lai-Hon; Lo, Hoi-Shing; Ng, Sze-Wing; Ma, Dik-Lung; Leung, Chung-Hang; Wong, Chun-Yuen

    2015-01-01

    Iridium(III) hydrido complexes containing N-heterocyclic carbene (NHC)-based pincer ligand 1,3-bis(1-butylimidazolin-2-ylidene)phenyl anion (C1^C^C1) or 1,3-bis(3-butylbenzimidazolin-2-ylidene)phenyl anion (C2^C^C2) and aromatic diimine (2,2?-bipyridine (bpy), 1,10-phenanthroline (phen), 4,4?-dimethyl-2,2?-bipyridine (Me2bpy), or dipyrido-[3,2-f:2?,3?-h]-quinoxaline (dpq)) in the form of [Ir(C^C^C)(N^N)(H)]+ have been prepared. Crystal structures for these complexes show that the IrCNHC distances are 2.043(5)2.056(5) . The hydride chemical shifts for complexes bearing C1^C^C1 (?20.6 to ?20.3?ppm) are more upfield than those with C2^C^C2 (?19.5 and ?19.2?ppm), revealing that C1^C^C1 is a better electron donor than C2^C^C2. Spectroscopic comparisons and time-dependent density functional theory (TD-DFT) calculations suggest that the lowest-energy electronic transition associated with these complexes (??=?340530?nm (????103?dm3 mol?1 cm?1)) originate from a d?(IrIII)????*(N^N) metal-to-ligand charge transfer transition, where the d?(IrIII) level contain significant contribution from the C^C^C ligands. All these complexes are emissive in the yellow-spectral region (553604?nm in CH3CN and CH2Cl2) upon photo-excitation with quantum yields of 10?310?1. PMID:26487542

  9. Luminescent Iridium(III) Complexes Supported by N-Heterocyclic Carbene-based C^C^C-Pincer Ligands and Aromatic Diimines

    NASA Astrophysics Data System (ADS)

    Chung, Lai-Hon; Lo, Hoi-Shing; Ng, Sze-Wing; Ma, Dik-Lung; Leung, Chung-Hang; Wong, Chun-Yuen

    2015-10-01

    Iridium(III) hydrido complexes containing N-heterocyclic carbene (NHC)-based pincer ligand 1,3-bis(1-butylimidazolin-2-ylidene)phenyl anion (C1^C^C1) or 1,3-bis(3-butylbenzimidazolin-2-ylidene)phenyl anion (C2^C^C2) and aromatic diimine (2,2?-bipyridine (bpy), 1,10-phenanthroline (phen), 4,4?-dimethyl-2,2?-bipyridine (Me2bpy), or dipyrido-[3,2-f:2?,3?-h]-quinoxaline (dpq)) in the form of [Ir(C^C^C)(N^N)(H)]+ have been prepared. Crystal structures for these complexes show that the IrCNHC distances are 2.043(5)2.056(5) . The hydride chemical shifts for complexes bearing C1^C^C1 (?20.6 to ?20.3?ppm) are more upfield than those with C2^C^C2 (?19.5 and ?19.2?ppm), revealing that C1^C^C1 is a better electron donor than C2^C^C2. Spectroscopic comparisons and time-dependent density functional theory (TD-DFT) calculations suggest that the lowest-energy electronic transition associated with these complexes (??=?340530?nm (????103?dm3 mol?1 cm?1)) originate from a d?(IrIII)????*(N^N) metal-to-ligand charge transfer transition, where the d?(IrIII) level contain significant contribution from the C^C^C ligands. All these complexes are emissive in the yellow-spectral region (553604?nm in CH3CN and CH2Cl2) upon photo-excitation with quantum yields of 10?310?1.

  10. Luminescent Iridium(III) Complexes Supported by N-Heterocyclic Carbene-based C^C^C-Pincer Ligands and Aromatic Diimines.

    PubMed

    Chung, Lai-Hon; Lo, Hoi-Shing; Ng, Sze-Wing; Ma, Dik-Lung; Leung, Chung-Hang; Wong, Chun-Yuen

    2015-01-01

    Iridium(III) hydrido complexes containing N-heterocyclic carbene (NHC)-based pincer ligand 1,3-bis(1-butylimidazolin-2-ylidene)phenyl anion (C(1)^C^C(1)) or 1,3-bis(3-butylbenzimidazolin-2-ylidene)phenyl anion (C(2)^C^C(2)) and aromatic diimine (2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), 4,4'-dimethyl-2,2'-bipyridine (Me2bpy), or dipyrido-[3,2-f:2',3'-h]-quinoxaline (dpq)) in the form of [Ir(C^C^C)(N^N)(H)](+) have been prepared. Crystal structures for these complexes show that the Ir-CNHC distances are 2.043(5)-2.056(5) . The hydride chemical shifts for complexes bearing C(1)^C^C(1) (-20.6 to -20.3?ppm) are more upfield than those with C(2)^C^C(2) (-19.5 and -19.2?ppm), revealing that C(1)^C^C(1) is a better electron donor than C(2)^C^C(2). Spectroscopic comparisons and time-dependent density functional theory (TD-DFT) calculations suggest that the lowest-energy electronic transition associated with these complexes (??=?340-530?nm (????10(3)?dm(3) mol(-1) cm(-1))) originate from a d?(Ir(III))????*(N^N) metal-to-ligand charge transfer transition, where the d?(Ir(III)) level contain significant contribution from the C^C^C ligands. All these complexes are emissive in the yellow-spectral region (553-604?nm in CH3CN and CH2Cl2) upon photo-excitation with quantum yields of 10(-3)-10(-1). PMID:26487542

  11. TRANSITION METAL ACTIVATION AND FUNCTIONALIZATION OF CARBON-HYDROGEN BONDS

    E-print Network

    Jones, William D.

    TRANSITION METAL ACTIVATION AND FUNCTIONALIZATION OF CARBON-HYDROGEN BONDS William D. Jones-H and C-C bond functionalization, and (4) carbon-fluorine bond activation. We have made progress in each in our proposal where we have had success. These include: (1) carbon-carbon bond cleavage reactions, (2

  12. (669)revision:2011-11-07modified:2011-11-08 NON COHEN ORACLE C.C.C

    E-print Network

    Shelah, Saharon

    (669)revision:2011-11-07modified:2011-11-08 NON COHEN ORACLE C.C.C SH669 SAHARON SHELAH Abstract. The oracle c.c.c. is closely related to Cohen forcing. During an iteration we can "omit a type"; i the parallel of the oracle c.c.c. and end with a criterion for extracting a subforcing (not a complete

  13. Novel carboncarbon bond formations for biocatalysis

    PubMed Central

    Resch, Verena; Schrittwieser, Joerg H; Siirola, Elina; Kroutil, Wolfgang

    2011-01-01

    Carboncarbon bond formation is the key transformation in organic synthesis to set up the carbon backbone of organic molecules. However, only a limited number of enzymatic CC bond forming reactions have been applied in biocatalytic organic synthesis. Recently, further name reactions have been accomplished for the first time employing enzymes on a preparative scale, for instance the Stetter and PictetSpengler reaction or oxidative CC bond formation. Furthermore, novel enzymatic CC bond forming reactions have been identified like benzylation of aromatics, intermolecular Diels-Alder or reductive coupling of carbon monoxide. PMID:21354781

  14. Evaluation by Rocket Combustor of C/C Composite Cooled Structure Using Metallic Cooling Tubes

    NASA Astrophysics Data System (ADS)

    Takegoshi, Masao; Ono, Fumiei; Ueda, Shuichi; Saito, Toshihito; Hayasaka, Osamu

    In this study, the cooling performance of a C/C composite material structure with metallic cooling tubes fixed by elastic force without chemical bonding was evaluated experimentally using combustion gas in a rocket combustor. The C/C composite chamber was covered by a stainless steel outer shell to maintain its airtightness. Gaseous hydrogen as a fuel and gaseous oxygen as an oxidizer were used for the heating test. The surface of these C/C composites was maintained below 1500 K when the combustion gas temperature was about 2800 K and the heat flux to the combustion chamber wall was about 9 MW/m2. No thermal damage was observed on the stainless steel tubes that were in contact with the C/C composite materials. The results of the heating test showed that such a metallic tube-cooled C/C composite structure is able to control the surface temperature as a cooling structure (also as a heat exchanger) as well as indicated the possibility of reducing the amount of coolant even if the thermal load to the engine is high. Thus, application of this metallic tube-cooled C/C composite structure to reusable engines such as a rocket-ramjet combined-cycle engine is expected.

  15. Journal of Molecular Catalysis A: Chemical 189 (2002) 157168 Cleavage of the carboncarbon bond in biphenylene

    E-print Network

    Jones, William D.

    2002-01-01

    Journal of Molecular Catalysis A: Chemical 189 (2002) 157168 Cleavage of the carboncarbon bond Biphenylene has proven to have a rich chemistry with transition metals. In many cases, the arylaryl CC bond Elsevier Science B.V. All rights reserved. Keywords: CC bond cleavage; Oxidative addition

  16. Hydrogen Induced C-C, C-N, & C-S Bond Activation on Pt & Ni Surfaces

    SciTech Connect

    Gland, J. L.

    2004-07-29

    The primary reactions investigated were chosen based on their importance in fuel and chemical production as well as in environmental remediation, and include reactions for hydrodesulfurization (HDS), hydrodenitrogenation (HDN), carbon-carbon hydrogenolysis, and hydrocarbon oxidation.

  17. Comparison of DFT with Traditional Methods for the Calculation of Vibrational Frequencies and Bond Energies

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W.; Arnold, James O. (Technical Monitor)

    1997-01-01

    The vibrational frequencies of MO2 are computed at many levels of theory, including HF, B3LYP, BP86, CASSCF, MP2, and CCSD(T). The computed results are compared with the available experimental results. Most of the methods fail for at least one state of the systems considered. The accuracy of the results and the origin of the observed failures are discussed. The B3LYP bond energies are compared with traditional methods for a variety of systems, ranging from FeCOn+ to SiCln and its positive ions. The cases where B3LYP differs from the traditional methods are discussed.

  18. Electronic structure, charge transfer and bonding in intermetallics using EELS and density functional theory[Electron Energy Loss Spectroscopy

    SciTech Connect

    Humphreys, C.J.; Botton, G.A.; Pankhurst, D.A.; Keast, V.J.; Temmerman, W.M.

    1999-07-01

    Electron energy loss spectroscopy and density functional theory have been used to show that there is a covalent component to the bonding in NiAl, CoAl and FeAl, between the transition metal atom and Al. There is no charge transfer and no ionic component to the bonding in NiAl and probably not in CoAl and FeAl. The bonding is non-stoichiometric NiAl is studied. Preliminary results are given for a {Sigma}{sub 3} boundary in NiAl.

  19. Nano-Bonding of Silicon Oxides-based surfaces at Low Temperature: Bonding Interphase Modeling via Molecular Dynamics and Characterization of Bonding Surfaces Topography, Hydro-affinity and Free Energy

    NASA Astrophysics Data System (ADS)

    Whaley, Shawn D.

    In this work, a new method, "Nanobonding(TM)" [1,2] is conceived and researched to bond Si-based surfaces, via nucleation and growth of a 2 D silicon oxide SiOxHx interphase connecting the surfaces at the nanoscale across macroscopic domains. Nanobonding cross-bridges two smooth surfaces put into mechanical contact in an O2/H 2O mixed ambient below T ?200 C via arrays of SiOxH x molecules connecting into a continuous macroscopic bonding interphase. Nano-scale surface planarization via wet chemical processing and new spin technology are compared via Tapping Mode Atomic Force Microscopy (TMAFM) , before and after nano-bonding. Nanobonding uses precursor phases, 2D nano-films of beta-cristobalite (beta-c) SiO2, nucleated on Si(100) via the Herbots-Atluri (H-A) method [1]. beta-c SiO2 on Si(100) is ordered and flat with atomic terraces over 20 nm wide, well above 2 nm found in native oxides. When contacted with SiO2 this ultra-smooth nanophase can nucleate and grow domains with cross-bridging molecular strands of hydroxylated SiOx, instead of point contacts. The high density of molecular bonds across extended terraces forms a strong bond between Si-based substrates, nano- bonding [2] the Si and silica. A new model of beta-cristobalite SiO2 with its <110> axis aligned along Si[100] direction is simulated via ab-initio methods in a nano-bonded stack with beta-c SiO2 in contact with amorphous SiO2 (a-SiO2), modelling cross-bridging molecular bonds between beta-c SiO2 on Si(100) and a-SiO2 as during nanobonding. Computed total energies are compared with those found for Si(100) and a-SiO2 and show that the presence of two lattice cells of !-c SiO2 on Si(100) and a-SiO2 lowers energy when compared to Si(100)/ a-SiO 2 Shadow cone calculations on three models of beta-c SiO2 on Si(100) are compared with Ion Beam Analysis of H-A processed Si(100). Total surface energy measurements via 3 liquid contact angle analysis of Si(100) after H-A method processing are also compared. By combining nanobonding experiments, TMAFM results, surface energy data, and ab-initio calculations, an atomistic model is derived and nanobonding is optimized. [1] US Patent 6,613,677 (9/2/03), 7,851,365 (12/14/10), [2] Patent Filed: 4/30/09, 10/1/2011

  20. Bent Bonds and Multiple Bonds.

    ERIC Educational Resources Information Center

    Robinson, Edward A.; Gillespie, Ronald J.

    1980-01-01

    Considers carbon-carbon multiple bonds in terms of Pauling's bent bond model, which allows direct calculation of double and triple bonds from the length of a CC single bond. Lengths of these multiple bonds are estimated from direct measurements on "bent-bond" models constructed of plastic tubing and standard kits. (CS)

  1. IBM XL C/C++ Enterprise Edition V8.0 for AIX Getting Started with XL C/C++

    E-print Network

    Hickman, Mark

    IBM XL C/C++ Enterprise Edition V8.0 for AIX Getting Started with XL C/C++ SC09-7997-00 #12;#12;IBM XL C/C++ Enterprise Edition V8.0 for AIX Getting Started with XL C/C++ SC09-7997-00 #12;Note! Before "Notices" on page 37. First Edition (September 2005) This edition applies to IBM® XL C/C++ Enterprise

  2. Active Metal Brazing and Characterization of Brazed Joints in C-C and C-SiC Composites to Copper-Clad-Molybdenum System

    NASA Technical Reports Server (NTRS)

    Singh, M.; Asthana, R.

    2008-01-01

    Carbon/carbon composites with CVI and resin-derived matrices, and C/SiC composites reinforced with T-300 carbon fibers in a CVI SiC matrix were joined to Cu-clad Mo using two Ag-Cu braze alloys, Cusil-ABA (1.75% Ti) and Ticusil (4.5% Ti). The brazed joints revealed good interfacial bonding, preferential precipitation of Ti at the composite/braze interface, and a tendency toward delamination in resin-derived C/C composite. Extensive braze penetration of the inter-fiber channels in the CVI C/C composites was observed. The Knoop microhardness (HK) distribution across the C/C joints indicated sharp gradients at the interface, and a higher hardness in Ticusil than in Cusil-ABA. For the C/SiC composite to Cu-clad-Mo joints, the effect of composite surface preparation revealed that ground samples did not crack whereas unground samples cracked. Calculated strain energy in brazed joints in both systems is comparable to the strain energy in a number of other ceramic/metal systems. Theoretical predictions of the effective thermal resistance suggest that such joined systems may be promising for thermal management applications.

  3. Bridging the momentum distribution and the potential energy surface of protons in hydrogen bonds

    NASA Astrophysics Data System (ADS)

    Morrone, Joseph; Lin, Lin; Car, Roberto; Parrinello, Michele

    2010-03-01

    Open path integral Car-Parrinello molecular dynamics studies have uncovered the proton momentum distribution in various phases of ice [1,2]. These systems exhibit a wide range of behavior, including symmetric hydrogen bonds and quantum tunneling. In this work, we provide an in-depth statistical analysis of the simulation results. This analysis reveals a direct relation between the open path formalism of quantum particles and their underlying potential energy surface. Application of this analysis to ice systems provides quantitative information about the principle axes of the potential energy surface that the proton experiences, and indicates that the oxygen-oxygen distance is a proper reaction coordinate for such systems. Our analysis also facilitates a direct observation of anharmonic effects along the principle axes. [1] J. A. Morrone and R. Car, Phys. Rev. Lett. 101, 17801, 2008. [2] J. A. Morrone, L. Lin and R. Car, J. Chem. Phys. 130, 204511, 2009.

  4. Evaluating interaction energies of weakly bonded systems using the Buckingham-Hirshfeld method

    SciTech Connect

    Krishtal, A.; Van Alsenoy, C.; Geerlings, P.

    2014-05-14

    We present the finalized Buckingham-Hirshfeld method (BHD-DFT) for the evaluation of interaction energies of non-bonded dimers with Density Functional Theory (DFT). In the method, dispersion energies are evaluated from static multipole polarizabilities, obtained on-the-fly from Coupled Perturbed Kohn-Sham calculations and partitioned into diatomic contributions using the iterative Hirshfeld partitioning method. The dispersion energy expression is distributed over four atoms and has therefore a higher delocalized character compared to the standard pairwise expressions. Additionally, full multipolar polarizability tensors are used as opposed to effective polarizabilities, allowing to retain the anisotropic character at no additional computational cost. A density dependent damping function for the BLYP, PBE, BP86, B3LYP, and PBE0 functionals has been implemented, containing two global parameters which were fitted to interaction energies and geometries of a selected number of dimers using a bi-variate RMS fit. The method is benchmarked against the S22 and S66 data sets for equilibrium geometries and the S22x5 and S66x8 data sets for interaction energies around the equilibrium geometry. Best results are achieved using the B3LYP functional with mean average deviation values of 0.30 and 0.24 kcal/mol for the S22 and S66 data sets, respectively. This situates the BHD-DFT method among the best performing dispersion inclusive DFT methods. Effect of counterpoise correction on DFT energies is discussed.

  5. Pd(II)-Catalyzed CH Activation/CC Cross-Coupling Reactions: Versatility and Practicality

    PubMed Central

    Chen, Xiao; Engle, Keary M.; Wang, Dong-Hui; Yu, Jin-Quan

    2009-01-01

    In the past decade, palladium-catalyzed CH activation/CC bond forming reactions have emerged as promising new catalytic transformations; however, development in this field is still at an early stage compared to the state of the art in cross-coupling reactions using aryl and alkyl halides. This Review begins with a brief introduction of four extensively investigated modes of catalysis for forming CC bonds from CH bonds: Pd(II)/Pd(0), Pd(II)/Pd(IV), Pd(0)/Pd(II)/Pd(IV) and Pd(0)/Pd(II) catalysis. More detailed discussion is then directed towards the recent development of Pd(II)-catalyzed coupling of CH bonds with organometallic reagents through a Pd(II)/Pd(0) catalytic cycle. Despite much progress made to date, improving the versatility and practicality of this new reaction remains a tremendous challenge. PMID:19557755

  6. Q: a molecular dynamics program for free energy calculations and empirical valence bond simulations in biomolecular systems.

    PubMed

    Marelius, J; Kolmodin, K; Feierberg, I; Aqvist, J

    1998-01-01

    A new molecular dynamics program for free energy calculations in biomolecular systems is presented. It is principally designed for free energy perturbation simulations, empirical valence bond calculations, and binding affinity estimation by linear interaction energy methods. Evaluation of ligand-binding selectivity and free energy profiles for nucleophile activation in two protein tyrosine phosphatases as well as absolute binding affinity estimation for a lysine-binding protein are given as examples. PMID:10522241

  7. C.C. Berndt: Professional 1 Following your Passion while

    E-print Network

    Alpay, S. Pamir

    C.C. Berndt: Professional 1 4/20/12 1 Following your Passion while Navigating the Bumps in the Road Chris Berndt Swinburne University of Technology; Melbourne Stony Brook University (SBU); NY-USA #12;C.C. Berndt: Professional Sydney Melbourne Where am I? Brisbane 2 2 #12;C.C. Berndt: Professional 3 85 km #1

  8. Bond dissociation energies in alcohols: kinetics and photochemical evidence regarding ion thermochemistry

    SciTech Connect

    Moylan, C.R.; Brauman, J.I.

    1984-07-19

    Gas-phase proton transfer from benzyl alcohol to fluoride ion is encounter controlled, whereas transfer from neopentyl alcohol to fluoride ion is slow. These observations suggest that the equilibrium gas-phase acidity of HF lies between those of the two alcohols, in contrast to the tabulated order. A small adjustment in the gas-phase acidities of alcohols not only makes the kinetics consistent but also resolves a long-standing discrepancy between RO-H bond energies measured by kinetic techniques and those determined by acidity/electron affinity data. It also accounts for the observed branching ratio in the IR laser photolysis of the neopentyl alcohol-fluoride ion complex. 21 references, 1 table.

  9. Communication: Towards the binding energy and vibrational red shift of the simplest organic hydrogen bond: Harmonic constraints for methanol dimer

    SciTech Connect

    Heger, Matthias; Suhm, Martin A.; Mata, Ricardo A.

    2014-09-14

    The discrepancy between experimental and harmonically predicted shifts of the OH stretching fundamental of methanol upon hydrogen bonding to a second methanol unit is too large to be blamed mostly on diagonal and off-diagonal anharmonicity corrections. It is shown that a decisive contribution comes from post-MP2 electron correlation effects, which appear not to be captured by any of the popular density functionals. We also identify that the major deficiency is in the description of the donor OH bond. Together with estimates for the electronic and harmonically zero-point corrected dimer binding energies, this work provides essential constraints for a quantitative description of this simple hydrogen bond. The spectroscopic dissociation energy is predicted to be larger than 18 kJ/mol and the harmonic OH-stretching fundamental shifts by about ?121 cm{sup ?1} upon dimerization, somewhat more than in the anharmonic experiment (?111 cm{sup ?1})

  10. Transport pathways for mobile ions in disordered solids from the analysis of energy-scaled bond-valence mismatch landscapes.

    PubMed

    Adams, Stefan; Rao, R Prasada

    2009-05-01

    Structure-property relationships provide valuable guidelines for a systematic development of functional materials. Here an augmented bond-valence approach is worked out that is linked directly to the energy scale. This energy-scaled bond-valence approach is then used to identify ion-conduction pathways and to establish structure-property relationships in complex disordered solids using lithium silicate glasses as model systems. Representative local structure models of glassy solid electrolytes as a basis for the pathway analysis are derived from molecular dynamics simulations. Predictions of the bond-valence model from a static structure model are compared to a complete trajectory analysis, showing a high degree of agreement. The method yields consistent results when changing the simulation force field and is applicable to a wide range of glasses. PMID:19370216

  11. Isotope dependent, temperature regulated, energy repartitioning in a low-barrier, short-strong hydrogen bonded cluster

    E-print Network

    Iyengar, Srinivasan S.

    Isotope dependent, temperature regulated, energy repartitioning in a low-barrier, short/deuterium isotope effects, in a fundamental organic hydrogen bonded system using multiple experimental infrared the isotopically labeled systems arises from an analysis of the simulated cluster spectroscopy and leads

  12. Microsolvation of methylmercury: structures, energies, bonding and NMR constants ((199)Hg, (13)C and (17)O).

    PubMed

    Flrez, Edison; Maldonado, Alejandro F; Aucar, Gustavo A; David, Jorge; Restrepo, Albeiro

    2016-01-21

    Hartree-Fock (HF) and second order perturbation theory (MP2) calculations within the scalar and full relativistic frames were carried out in order to determine the equilibrium geometries and interaction energies between cationic methylmercury (CH3Hg(+)) and up to three water molecules. A total of nine structures were obtained. Bonding properties were analyzed using the Quantum Theory of Atoms In Molecules (QTAIM). The analyses of the topology of electron densities reveal that all structures exhibit a partially covalent HgO interaction between methylmercury and one water molecule. Consideration of additional water molecules suggests that they solvate the (CH3HgOH2)(+) unit. Nuclear magnetic shielding constants ?((199)Hg), ?((13)C) and ?((17)O), as well as indirect spin-spin coupling constants J((199)Hg-(13)C), J((199)Hg-(17)O) and J((13)C-(17)O), were calculated for each one of the geometries. Thermodynamic stability and the values of NMR constants correlate with the ability of the system to directly coordinate oxygen atoms of water molecules to the mercury atom in methylmercury and with the formation of hydrogen bonds among solvating water molecules. Relativistic effects account for 11% on ?((13)C) and 14% on ?((17)O), which is due to the presence of Hg (heavy atom on light atom, HALA effect), while the relativistic effects on ?((199)Hg) are close to 50% (heavy atom on heavy atom itself, HAHA effect). J-coupling constants are highly influenced by relativity when mercury is involved as in J((199)Hg-(13)C) and J((199)Hg-(17)O). On the other hand, our results show that the values of NMR constants for carbon and oxygen, atoms which are connected through mercury (C-HgO), are highly correlated and are greatly influenced by the presence of water molecules. Water molecules introduce additional electronic effects to the relativistic effects due to the mercury atom. PMID:26670708

  13. Effect of ultrasonic energy on nanoscale interfacial structure in copper wire bonding on aluminium pads

    NASA Astrophysics Data System (ADS)

    Xu, H.; Liu, C.; Silberschmidt, V. V.; Chen, Z.; Acoff, V. L.

    2011-04-01

    The effect of ultrasonic vibration on nanoscale interfacial structure of thermosonic copper wire bonding on aluminium pads was investigated. It was found that bonding strength was determined by the extent of fragmentation of a native aluminium oxide overlayer (5-10 nm thick) on aluminium pads, forming paths for formation of intermetallic compound CuAl2 in areas of direct contact of bonded metal surfaces. The degree of fracture of the oxide layer was strongly affected by a level of ultrasonic power.

  14. Potential energy surface discontinuities in local correlation methods.

    PubMed

    Russ, Nicholas J; Crawford, T Daniel

    2004-07-01

    We have examined the occurrence of discontinuities in bond-breaking potential energy surfaces given by local correlation methods based on the Pulay-Saeb orbital domain approach. Our analysis focuses on three prototypical dissociating systems: the C-F bond in fluoromethane, the C-C bond in singlet, ketene, and the central C-C bond in propadienone. We find that such discontinuities do not occur in cases of homolytic bond cleavage due to the inability of the Pipek-Mezey orbital localization method to separate singlet-coupled charges on distant fragments. However, for heterolytic bond cleavage, such as that observed in singlet ketene and propadienone, discontinuities occur both at stretched geometries and near equilibrium. These discontinuities are usually small, but may be of the same order of magnitude as the localization error in some cases. PMID:15260595

  15. Potential energy surface discontinuities in local correlation methods

    NASA Astrophysics Data System (ADS)

    Russ, Nicholas J.; Crawford, T. Daniel

    2004-07-01

    We have examined the occurence of discontinuities in bond-breaking potential energy surfaces given by local correlation methods based on the Pulay-Saeb orbital domain approach. Our analysis focuses on three prototypical dissociating systems: the C-F bond in fluoromethane, the C-C bond in singlet, ketene, and the central C-C bond in propadienone. We find that such discontinuities do not occur in cases of homolytic bond cleavage due to the inability of the Pipek-Mezey orbital localization method to separate singlet-coupled charges on distant fragments. However, for heterolytic bond cleavage, such as that observed in singlet ketene and propadienone, discontinuities occur both at stretched geometries and near equilibrium. These discontinuities are usually small, but may be of the same order of magnitude as the localization error in some cases.

  16. Measurements of $?(3686) \\to K^{-} ?\\bar?^{+} +c.c.$ and $?(3686) \\to ?K^{-} ?\\bar?^{+} +c.c$

    E-print Network

    BESIII Collaboration; M. Ablikim; M. N. Achasov; X. C. Ai; O. Albayrak; M. Albrecht; D. J. Ambrose; A. Amoroso; F. F. An; Q. An; J. Z. Bai; R. Baldini Ferroli; Y. Ban; D. W. Bennett; J. V. Bennett; M. Bertani; D. Bettoni; J. M. Bian; F. Bianchi; E. Boger; O. Bondarenko; I. Boyko; R. A. Briere; H. Cai; X. Cai; O. Cakir; A. Calcaterra; G. F. Cao; S. A. Cetin; J. F. Chang; G. Chelkov; G. Chen; H. S. Chen; H. Y. Chen; J. C. Chen; M. L. Chen; S. J. Chen; X. Chen; X. R. Chen; Y. B. Chen; H. P. Cheng; X. K. Chu; G. Cibinetto; D. Cronin-Hennessy; H. L. Dai; J. P. Dai; A. Dbeyssi; D. Dedovich; Z. Y. Deng; A. Denig; I. Denysenko; M. Destefanis; F. DeMori; Y. Ding; C. Dong; J. Dong; L. Y. Dong; M. Y. Dong; S. X. Du; P. F. Duan; J. Z. Fan; J. Fang; S. S. Fang; X. Fang; Y. Fang; L. Fava; F. Feldbauer; G. Felici; C. Q. Feng; E. Fioravanti; M. Fritsch; C. D. Fu; Q. Gao; X. Y. Gao; Y. Gao; Z. Gao; I. Garzia; C. Geng; K. Goetzen; W. X. Gong; W. Gradl; M. Greco; M. H. Gu; Y. T. Gu; Y. H. Guan; A. Q. Guo; L. B. Guo; Y. Guo; Y. P. Guo; Z. Haddadi; A. Hafner; S. Han; Y. L. Han; X. Q. Hao; F. A. Harris; K. L. He; Z. Y. He; T. Held; Y. K. Heng; Z. L. Hou; C. Hu; H. M. Hu; J. F. Hu; T. Hu; Y. Hu; G. M. Huang; G. S. Huang; H. P. Huang; J. S. Huang; X. T. Huang; Y. Huang; T. Hussain; Q. Ji; Q. P. Ji; X. B. Ji; X. L. Ji; L. L. Jiang; L. W. Jiang; X. S. Jiang; J. B. Jiao; Z. Jiao; D. P. Jin; S. Jin; T. Johansson; A. Julin; N. Kalantar-Nayestanaki; X. L. Kang; X. S. Kang; M. Kavatsyuk; B. C. Ke; R. Kliemt; B. Kloss; O. B. Kolcu; B. Kopf; M. Kornicer; W. Khn; A. Kupsc; W. Lai; J. S. Lange; M. Lara; P. Larin; C. Leng; C. H. Li; Cheng Li; D. M. Li; F. Li; G. Li; H. B. Li; J. C. Li; Jin Li; K. Li; K. Li; Lei Li; P. R. Li; T. Li; W. D. Li; W. G. Li; X. L. Li; X. M. Li; X. N. Li; X. Q. Li; Z. B. Li; H. Liang; Y. F. Liang; Y. T. Liang; G. R. Liao; D. X. Lin; B. J. Liu; C. X. Liu; F. H. Liu; Fang Liu; Feng Liu; H. B. Liu; H. H. Liu; H. H. Liu; H. M. Liu; J. Liu; J. P. Liu; J. Y. Liu; K. Liu; K. Y. Liu; L. D. Liu; P. L. Liu; Q. Liu; S. B. Liu; X. Liu; X. X. Liu; Y. B. Liu; Z. A. Liu; Zhiqiang Liu; Zhiqing Liu; H. Loehner; X. C. Lou; H. J. Lu; J. G. Lu; R. Q. Lu; Y. Lu; Y. P. Lu; C. L. Luo; M. X. Luo; T. Luo; X. L. Luo; M. Lv; X. R. Lyu; F. C. Ma; H. L. Ma; L. L. Ma; Q. M. Ma; S. Ma; T. Ma; X. N. Ma; X. Y. Ma; F. E. Maas; M. Maggiora; Q. A. Malik; Y. J. Mao; Z. P. Mao; S. Marcello; J. G. Messchendorp; J. Min; T. J. Min; R. E. Mitchell; X. H. Mo; Y. J. Mo; C. Morales Morales; K. Moriya; N. Yu. Muchnoi; H. Muramatsu; Y. Nefedov; F. Nerling; I. B. Nikolaev; Z. Ning; S. Nisar; S. L. Niu; X. Y. Niu; S. L. Olsen; Q. Ouyang; S. Pacetti; P. Patteri; M. Pelizaeus; H. P. Peng; K. Peters; J. Pettersson; J. L. Ping; R. G. Ping; R. Poling; Y. N. Pu; M. Qi; S. Qian; C. F. Qiao; L. Q. Qin; N. Qin; X. S. Qin; Y. Qin; Z. H. Qin; J. F. Qiu; K. H. Rashid; C. F. Redmer; H. L. Ren; M. Ripka; G. Rong; X. D. Ruan; V. Santoro; A. Sarantsev; M. Savri; K. Schoenning; S. Schumann; W. Shan; M. Shao; C. P. Shen; P. X. Shen; X. Y. Shen; H. Y. Sheng; W. M. Song; X. Y. Song; S. Sosio; S. Spataro; G. X. Sun; J. F. Sun; S. S. Sun; Y. J. Sun; Y. Z. Sun; Z. J. Sun; Z. T. Sun; C. J. Tang; X. Tang; I. Tapan; E. H. Thorndike; M. Tiemens; D. Toth; M. Ullrich; I. Uman; G. S. Varner; B. Wang; B. L. Wang; D. Wang; D. Y. Wang; K. Wang; L. L. Wang; L. S. Wang; M. Wang; P. Wang; P. L. Wang; Q. J. Wang; S. G. Wang; W. Wang; X. F. Wang; Y. D. Wang; Y. F. Wang; Y. Q. Wang; Z. Wang; Z. G. Wang; Z. H. Wang; Z. Y. Wang; T. Weber; D. H. Wei; J. B. Wei; P. Weidenkaff; S. P. Wen; U. Wiedner; M. Wolke; L. H. Wu; Z. Wu; L. G. Xia; Y. Xia; D. Xiao; Z. J. Xiao; Y. G. Xie; Q. L. Xiu; G. F. Xu; L. Xu; Q. J. Xu; Q. N. Xu; X. P. Xu; L. Yan; W. B. Yan; W. C. Yan; Y. H. Yan; H. X. Yang; L. Yang; Y. Yang; Y. X. Yang; H. Ye; M. Ye; M. H. Ye; J. H. Yin; B. X. Yu; C. X. Yu; H. W. Yu; J. S. Yu; C. Z. Yuan; W. L. Yuan; Y. Yuan; A. Yuncu; A. A. Zafar; A. Zallo; Y. Zeng; B. X. Zhang; B. Y. Zhang; C. Zhang; C. C. Zhang; D. H. Zhang; H. H. Zhang; H. Y. Zhang; J. J. Zhang; J. L. Zhang; J. Q. Zhang; J. W. Zhang; J. Y. Zhang; J. Z. Zhang; K. Zhang; L. Zhang; S. H. Zhang; X. Y. Zhang; Y. Zhang; Y. H. Zhang; Y. T. Zhang; Z. H. Zhang; Z. P. Zhang; Z. Y. Zhang; G. Zhao; J. W. Zhao; J. Y. Zhao; J. Z. Zhao; Lei Zhao; Ling Zhao; M. G. Zhao; Q. Zhao; Q. W. Zhao; S. J. Zhao; T. C. Zhao; Y. B. Zhao; Z. G. Zhao; A. Zhemchugov; B. Zheng; J. P. Zheng; W. J. Zheng; Y. H. Zheng; B. Zhong; L. Zhou; Li Zhou; X. Zhou; X. K. Zhou; X. R. Zhou; X. Y. Zhou; K. Zhu; K. J. Zhu; S. Zhu; X. L. Zhu; Y. C. Zhu; Y. S. Zhu; Z. A. Zhu; J. Zhuang; L. Zotti; B. S. Zou; J. H. Zou

    2015-04-08

    Using a sample of $1.06\\times10^8\\ \\psip$ events produced in $e^+e^-$ collisions at $\\sqrt{s}$ = 3.686 GeV and collected with the BESIII detector at the BEPCII collider, we present studies of the decays $\\klx+c.c.$ and $\\gklx+c.c.$. We observe two hyperons, $\\Xi(1690)^-$ and $\\Xi(1820)^-$, in the $K^-\\Lambda$ invariant mass distribution in the decay $\\klx+c.c.$ with significances of $4.9 \\sigma$ and $6.2 \\sigma$, respectively. The branching fractions of $\\klx+c.c.$, $\\ksx+c.c.$, $\\psip\\to\\gamma \\chi_{cJ}\\to \\gamma K^- \\Lambda \\bar{\\Xi}^+ +c.c.$ $(J=0,\\ 1,\\ 2)$, and $\\psip\\to \\Xi(1690/1820)^{-} \\bar{\\Xi}^++c.c$ with subsequent decay $\\Xi(1690/1820)^-\\to K^-\\Lambda$ are measured for the first time.

  17. Describing the chemical bonding in C70 and C70O3 - A quantum chemical topology study

    NASA Astrophysics Data System (ADS)

    Bil, Andrzej; Latajka, Zdzis?aw; Hutter, Jrg; Morrison, Carole A.

    2014-03-01

    Cc-Cc and Ca-Cb bonds in C70 have dominant characteristics of double bonds, whereas the remaining six other types of bonds are single bonds with contributions from ?-electron density. 'Single' bonds can act as active sites in chemical reactions which would typically require a multiple bond, such as addition of an ozone molecule, due to the fact that all adjacent bonds can serve as an efficient source of ?-electron density. Thus any alteration in the electron density distribution following functionalization has far-reaching impact. We note that formation of the most stable ozonide isomer causes the smallest total perturbation in the electron density of the parent fullerene and C-C bond evolution correlates well with the shape of the minimum energy path for the ozone ring opening reaction on the fullerene surface. Finally, we observe that the O-O bond in C70O3 is protocovalent, and as such resembles the O-O bond in H2O2.

  18. Coordination-resolved local bond contraction and electron binding-energy entrapment of Si atomic clusters and solid skins

    SciTech Connect

    Bo, Maolin; Huang, Yongli; Zhang, Ting; Wang, Yan E-mail: ecqsun@ntu.edu.sg; Zhang, Xi; Li, Can; Sun, Chang Q. E-mail: ecqsun@ntu.edu.sg

    2014-04-14

    Consistency between x-ray photoelectron spectroscopy measurements and density-function theory calculations confirms our bond order-length-strength notation-incorporated tight-binding theory predictions on the quantum entrapment of Si solid skin and atomic clusters. It has been revealed that bond-order deficiency shortens and strengthens the Si-Si bond, which results in the local densification and quantum entrapment of the core and valence electrons. Unifying Si clusters and Si(001) and (111) skins, this mechanism has led to quantification of the 2p binding energy of 96.089?eV for an isolated Si atom, and their bulk shifts of 2.461?eV. Findings evidence the significance of atomic undercoordination that is of great importance to device performance.

  19. Estimation of individual binding energies in some dimers involving multiple hydrogen bonds using topological properties of electron charge density

    NASA Astrophysics Data System (ADS)

    Ebrahimi, A.; Habibi Khorassani, S. M.; Delarami, H.

    2009-11-01

    Individual hydrogen bond (HB) energies have been estimated in several systems involving multiple HBs such as adenine-thymine and guanine-cytosine using electron charge densities calculated at X⋯H hydrogen bond critical points (HBCPs) by atoms in molecules (AIM) method at B3LYP/6-311++G ?? and MP2/6-311++G ?? levels. A symmetrical system with two identical H bonds has been selected to search for simple relations between ?HBCP and individual EHB. Correlation coefficient between EHB and ?HBCP in the base of linear, quadratic, and exponential equations are acceptable and equal to 0.95. The estimated individual binding energies EHB are in good agreement with the results of atom-replacement approach and natural bond orbital analysis (NBO). The EHB values estimated from ? values at H⋯X BCP are in satisfactory agreement with the main geometrical parameter H⋯X. With respect to the obtained individual binding energies, the strength of a HB depends on the substituent and the cooperative effects of other HBs.

  20. Accounting for the differences in the structures and relative energies of the highly homoatomic np pi-np pi (n > or = 3)-bonded S2I4 2+, the Se-I pi-bonded Se2I4 2+, and their higher-energy isomers by AIM, MO, NBO, and VB methodologies.

    PubMed

    Brownridge, Scott; Crawford, Margaret-Jane; Du, Hongbin; Harcourt, Richard D; Knapp, Carsten; Laitinen, Risto S; Passmore, Jack; Rautiainen, J Mikko; Suontamo, Reijo J; Valkonen, Jussi

    2007-02-01

    The bonding in the highly homoatomic np pi-np pi (n > or = 3)-bonded S2I42+ (three sigma + two pi bonds), the Se-I pi-bonded Se2I42+ (four sigma + one pi bonds), and their higher-energy isomers have been studied using modern DFT and ab initio calculations and theoretical analysis methods: atoms in molecules (AIM), molecular orbital (MO), natural bond orbital (NBO), and valence bond (VB) analyses, giving their relative energies, theoretical bond orders, and atomic charges. The aim of this work was to seek theory-based answers to four main questions: (1) Are the previously proposed simple pi*-pi* bonding models valid for S2I42+ and Se2I42+? (2) What accounts for the difference in the structures of S2I42+ and Se2I42+? (3) Why are the classically bonded isolobal P2I4 and As2I4 structures not adopted? (4) Is the high experimentally observed S-S bond order supported by theoretical bond orders, and how does it relate to high bond orders between other heavier main group elements? The AIM analysis confirmed the high bond orders and established that the weak bonds observed in S2I42+ and Se2I42+ are real and the bonding in these cations is covalent in nature. The full MO analysis confirmed that S2I42+ contains three sigma and two pi bonds, that the positive charge is essentially equally distributed over all atoms, that the bonding between S2 and two I2+ units in S2I42+ is best described by two mutually perpendicular 4c2e pi*-pi* bonds, and that in Se2I42+, two SeI2+ moieties are joined by a 6c2e pi*-pi* bond, both in agreement with previously suggested models. The VB treatment provided a complementary approach to MO analysis and provided insight how the formation of the weak bonds affects the other bonds. The NBO analysis and the calculated AIM charges showed that the minimization of the electrostatic repulsion between EI2+ units (E = S, Se) and the delocalization of the positive charge are the main factors that explain why the nonclassical structures are favored for S2I42+ and Se2I42+. The difference in the structures of S2I42+ and Se2I42+ is related to the high strength of the S-S pi bond compared to the weak S-I sigma bond and the additional stabilization from increased delocalization of positive charge in the structure of S2I42+ compared to the structure of Se2I42+. The investigation of the E2X42+ series (E = S, Se, Te; X = Cl, Br, I) revealed that only S2I42+ adopts the highly np pi-np pi (n > or = 3)-bonded structure, while all other dications favor the pi-bonded Se2I42+ structure. Theoretical bond order calculations for S2I42+ confirm the previously presented experimentally based bond orders for S-S (2.1-2.3) and I-I (1.3-1.5) bonds. The S-S bond is determined to have the highest reported S-S bond order in an isolated compound and has a bond order that is either similar to or slightly less than the Si-Si bond order in the proposed triply bonded [(Me3Si)2CH]2(iPr)SiSi triple bond SiSi(iPr)[CH(SiMe3)2]2 depending on the definition of bond orders used. PMID:17257010

  1. Universal Bronsted-Evans-Polanyi Relations for C-C, C-O, C-N, N-O, N-N, and O-O Dissociation Reactions

    SciTech Connect

    Wang, Shengguang

    2010-10-27

    It is shown that for all the essential bond forming and bond breaking reactions on metal surfaces, the reactivity of the metal surface correlates linearly with the reaction energy in a single universal relation. Such correlations provide an easy way of establishing trends in reactivity among the different transition metals.

  2. Autyomatic Differentiation of C/C++

    Energy Science and Technology Software Center (ESTSC)

    2005-11-14

    Automatic differentiation (AD) tools mechanize the process of developing code for the computation of derivatives. AD avoids the inaccuracies inherent in numerical approximations. Furthermore, sophisticated AD algoirthms can often produce c ode that is more reliable and more efficient than code written by an expert programmer. ADIC is the first and only AD tool for C and C++ based on compiler technology. This compiler foundation makes possible analyses and optimizations not available in toos basedmoreon operator overloading. The earliest implementations of ADIC included support for ANSI C applications, ADIC 2.0 lverages EDG, a commercial C/C++ parser, to provide robust C++ differentiation support. Modern AD tools, including ADIC are implemented in a modular way, aiming to isolate language-dependent program analyses and semantic transformations. The component design leads to much higher implementation quality because the different components can be implemented by experts in each of the different domains involved. For example, a compiler expert can focus on parsing, canonicalizing, and unparising C and C++, while an expert in graph theory and algorithms can produce new differentiation modules without having to worry about the complexity of parsing and generating C++ code. Thsi separation of concerns was achieved through the use of language-independent program analysis interfaces (in collaboration with researcgers at Rice University) and a language-independent XML representation of the computational portions of programs (XAIF). In addition to improved robustness and faster development times, this design naturally enables the reuse of program analysis algorithms and differentiation modules in compiler-based AD tools for other languages. In fact, the analysis and differention components are used in both ADIC and the Open AD Fortran front-end (based on Rice's Open64 compiler.less

  3. High-energy, stable and recycled molecular solar thermal storage materials using AZO/graphene hybrids by optimizing hydrogen bonds

    NASA Astrophysics Data System (ADS)

    Luo, Wen; Feng, Yiyu; Qin, Chengqun; Li, Man; Li, Shipei; Cao, Chen; Long, Peng; Liu, Enzuo; Hu, Wenping; Yoshino, Katsumi; Feng, Wei

    2015-10-01

    An important method for establishing a high-energy, stable and recycled molecular solar heat system is by designing and preparing novel photo-isomerizable molecules with a high enthalpy and a long thermal life by controlling molecular interactions. A meta- and ortho-bis-substituted azobenzene chromophore (AZO) is covalently grafted onto reduced graphene oxide (RGO) for solar thermal storage materials. High grafting degree and close-packed molecules enable intermolecular hydrogen bonds (H-bonds) for both trans-(E) and cis-(Z) isomers of AZO on the surface of nanosheets, resulting in a dramatic increase in enthalpy and lifetime. The metastable Z-form of AZO on RGO is thermally stabilized with a half-life of 52 days by steric hindrance and intermolecular H-bonds calculated using density functional theory (DFT). The AZO-RGO fuel shows a high storage capacity of 138 Wh kg-1 by optimizing intermolecular H-bonds with a good cycling stability for 50 cycles induced by visible light at 520 nm. Our work opens up a new method for making advanced molecular solar thermal storage materials by tuning molecular interactions on a nano-template.An important method for establishing a high-energy, stable and recycled molecular solar heat system is by designing and preparing novel photo-isomerizable molecules with a high enthalpy and a long thermal life by controlling molecular interactions. A meta- and ortho-bis-substituted azobenzene chromophore (AZO) is covalently grafted onto reduced graphene oxide (RGO) for solar thermal storage materials. High grafting degree and close-packed molecules enable intermolecular hydrogen bonds (H-bonds) for both trans-(E) and cis-(Z) isomers of AZO on the surface of nanosheets, resulting in a dramatic increase in enthalpy and lifetime. The metastable Z-form of AZO on RGO is thermally stabilized with a half-life of 52 days by steric hindrance and intermolecular H-bonds calculated using density functional theory (DFT). The AZO-RGO fuel shows a high storage capacity of 138 Wh kg-1 by optimizing intermolecular H-bonds with a good cycling stability for 50 cycles induced by visible light at 520 nm. Our work opens up a new method for making advanced molecular solar thermal storage materials by tuning molecular interactions on a nano-template. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03558a

  4. Chemical Bonds I

    ERIC Educational Resources Information Center

    Sanderson, R. T.

    1972-01-01

    Chemical bonding is discussed from a bond energy, rather than a wave mechanics, viewpoint. This approach is considered to be more suitable for the average student. (The second part of the article will appear in a later issue of the journal.) (AL)

  5. Unraveling the interplay between hydrogen bonding and rotational energy barrier to fine-tune the properties of triazine molecular glasses.

    PubMed

    Laventure, Audrey; De Grandpr, Guillaume; Soldera, Armand; Lebel, Olivier; Pellerin, Christian

    2016-01-21

    Mexylaminotriazine derivatives form molecular glasses with outstanding glass-forming ability (GFA), high resistance to crystallization (glass kinetic stability, GS), and a glass transition temperature (Tg) above room temperature that can be conveniently modulated by selection of the headgroup and ancillary groups. A common feature of all these compounds is their secondary amino linkers, suggesting that they play a critical role in their GFA and GS for reasons that remain unclear because they can simultaneously form hydrogen (H) bonds and lead to a high interconversion energy barrier between different rotamers. To investigate independently and better control the influence of H bonding capability and rotational energy barrier on Tg, GFA and GS, a library of twelve analogous molecules was synthesized with different combinations of NH, NMe and O linkers. Differential scanning calorimetry (DSC) revealed that these compounds form, with a single exception, kinetically stable glasses with Tg values spanning a very broad range from -25 to 94 C. While variable temperature infrared spectroscopy combined to chemometrics reveals that, on average, around 60% of the NH groups are still H-bonded as high as 40 C above Tg, critical cooling rates obtained by DSC clearly show that molecules without H-bond donating linkers also present an outstanding GFA, meaning that H bonding plays a dominant role in controlling Tg but is not required to prevent crystallization. It is a high interconversion energy barrier, provoking a distribution of rotamers, that most efficiently promotes both GFA and resistance to crystallization. These new insights pave the way to more efficient glass engineering by extending the possible range of accessible Tg, allowing in particular the preparation of homologous glass-formers with high GS at ambient temperature in either the viscous or vitreous state. PMID:26675473

  6. Sticker Bonding.

    ERIC Educational Resources Information Center

    Frazier, Laura Corbin

    2000-01-01

    Introduces a science activity on the bonding of chemical compounds. Assigns students the role of either a cation or anion and asks them to write the ions they may bond with. Assesses students' understanding of charge, bonding, and other concepts. (YDS)

  7. Bond Issues.

    ERIC Educational Resources Information Center

    Pollack, Rachel H.

    2000-01-01

    Notes trends toward increased borrowing by colleges and universities and offers guidelines for institutions that are considering issuing bonds to raise money for capital projects. Discussion covers advantages of using bond financing, how use of bonds impacts on traditional fund raising, other cautions and concerns, and some troubling aspects of

  8. Adhesive-Bonded Composite Joint Analysis with Delaminated Surface Ply Using Strain-Energy Release Rate

    NASA Technical Reports Server (NTRS)

    Chadegani, Alireza; Yang, Chihdar; Smeltzer, Stanley S. III

    2012-01-01

    This paper presents an analytical model to determine the strain energy release rate due to an interlaminar crack of the surface ply in adhesively bonded composite joints subjected to axial tension. Single-lap shear-joint standard test specimen geometry with thick bondline is followed for model development. The field equations are formulated by using the first-order shear-deformation theory in laminated plates together with kinematics relations and force equilibrium conditions. The stress distributions for the adherends and adhesive are determined after the appropriate boundary and loading conditions are applied and the equations for the field displacements are solved. The system of second-order differential equations is solved to using the symbolic computation tool Maple 9.52 to provide displacements fields. The equivalent forces at the tip of the prescribed interlaminar crack are obtained based on interlaminar stress distributions. The strain energy release rate of the crack is then determined by using the crack closure method. Finite element analyses using the J integral as well as the crack closure method are performed to verify the developed analytical model. It has been shown that the results using the analytical method correlate well with the results from the finite element analyses. An attempt is made to predict the failure loads of the joints based on limited test data from the literature. The effectiveness of the inclusion of bondline thickness is justified when compared with the results obtained from the previous model in which a thin bondline and uniform adhesive stresses through the bondline thickness are assumed.

  9. Chemical bonding in view of electron charge density and kinetic energy density descriptors.

    PubMed

    Jacobsen, Heiko

    2009-05-01

    Stalke's dilemma, stating that different chemical interpretations are obtained when one and the same density is interpreted either by means of natural bond orbital (NBO) and subsequent natural resonance theory (NRT) application or by the quantum theory of atoms in molecules (QTAIM), is reinvestigated. It is shown that within the framework of QTAIM, the question as to whether for a given molecule two atoms are bonded or not is only meaningful in the context of a well-defined reference geometry. The localized-orbital-locator (LOL) is applied to map out patterns in covalent bonding interaction, and produces results that are consistent for a variety of reference geometries. Furthermore, LOL interpretations are in accord with NBO/NRT, and assist in an interpretation in terms of covalent bonding. PMID:19090572

  10. Experimental and theoretical investigations of energy transfer and hydrogen-bond breaking in small water and HCl clusters.

    PubMed

    Samanta, Amit K; Czak, Gbor; Wang, Yimin; Mancini, John S; Bowman, Joel M; Reisler, Hanna

    2014-08-19

    Water is one of the most pervasive molecules on earth and other planetary bodies; it is the molecule that is searched for as the presumptive precursor to extraterrestrial life. It is also the paradigm substance illustrating ubiquitous hydrogen bonding (H-bonding) in the gas phase, liquids, crystals, and amorphous solids. Moreover, H-bonding with other molecules and between different molecules is of the utmost importance in chemistry and biology. It is no wonder, then, that for nearly a century theoreticians and experimentalists have tried to understand all aspects of H-bonding and its influence on reactivity. It is somewhat surprising, therefore, that several fundamental aspects of H-bonding that are particularly important for benchmarking theoretical models have remained unexplored experimentally. For example, even the binding strength between two gas-phase water molecules has never been determined with sufficient accuracy for comparison with high-level electronic structure calculations. Likewise, the effect of cooperativity (nonadditivity) in small H-bonded networks is not known with sufficient accuracy. An even greater challenge for both theory and experiment is the description of the dissociation dynamics of H-bonded small clusters upon acquiring vibrational excitation. This is because of the long lifetimes of many clusters, which requires running classical trajectories for many nanoseconds to achieve dissociation. In this Account, we describe recent progress and ongoing research that demonstrates how the combined and complementary efforts of theory and experiment are enlisted to determine bond dissociation energies (D0) of small dimers and cyclic trimers of water and HCl with unprecedented accuracy, describe dissociation dynamics, and assess the effects of cooperativity. The experimental techniques rely on IR excitation of H-bonded X-H stretch vibrations, measuring velocity distributions of fragments in specific rovibrational states, and determining product state distributions at the pair-correlation level. The theoretical methods are based on high-level ab initio potential energy surfaces used in quantum and classical dynamical calculations. We achieve excellent agreement on D0 between theory and experiments for all of the clusters that we have compared, as well as for cooperativity in ring trimers of water and HCl. We also show that both the long-range and the repulsive parts of the potential must be involved in bond breaking. We explain why H-bonds are so resilient and hard to break, and we propose that a common motif in the breaking of cyclic trimers is the opening of the ring following transfer of one quantum of stretch excitation to form open-chain structures that are weakly bound. However, it still takes many vibrational periods to release one monomer fragment from the open-chain structures. Our success with water and HCl dimers and trimers led us to embark on a more ambitious project: studies of mixed water and HCl small clusters. These clusters eventually lead to ionization of HCl and serve as prototypes of acid dissociation in water. Measurements and calculations of such ionizations are yet to be achieved, and we are now characterizing these systems by adding monomers one at a time. We describe our completed work on the HCl-H2O dimer and mention our recent theoretical results on larger mixed clusters. PMID:25072730

  11. High-energy, stable and recycled molecular solar thermal storage materials using AZO/graphene hybrids by optimizing hydrogen bonds.

    PubMed

    Luo, Wen; Feng, Yiyu; Qin, Chengqun; Li, Man; Li, Shipei; Cao, Chen; Long, Peng; Liu, Enzuo; Hu, Wenping; Yoshino, Katsumi; Feng, Wei

    2015-10-01

    An important method for establishing a high-energy, stable and recycled molecular solar heat system is by designing and preparing novel photo-isomerizable molecules with a high enthalpy and a long thermal life by controlling molecular interactions. A meta- and ortho-bis-substituted azobenzene chromophore (AZO) is covalently grafted onto reduced graphene oxide (RGO) for solar thermal storage materials. High grafting degree and close-packed molecules enable intermolecular hydrogen bonds (H-bonds) for both trans-(E) and cis-(Z) isomers of AZO on the surface of nanosheets, resulting in a dramatic increase in enthalpy and lifetime. The metastable Z-form of AZO on RGO is thermally stabilized with a half-life of 52 days by steric hindrance and intermolecular H-bonds calculated using density functional theory (DFT). The AZO-RGO fuel shows a high storage capacity of 138 Wh kg(-1) by optimizing intermolecular H-bonds with a good cycling stability for 50 cycles induced by visible light at 520 nm. Our work opens up a new method for making advanced molecular solar thermal storage materials by tuning molecular interactions on a nano-template. PMID:26289389

  12. The influence of large-amplitude librational motion on the hydrogen bond energy for alcohol-water complexes.

    PubMed

    Andersen, J; Heimdal, J; Wugt Larsen, R

    2015-10-01

    The far-infrared absorption spectra have been recorded for hydrogen-bonded complexes of water with methanol and t-butanol embedded in cryogenic neon matrices at 2.8 K. The partial isotopic substitution of individual subunits enabled by a dual inlet deposition procedure provides for the first time unambiguous assignments of the intermolecular high-frequency out-of-plane and low-frequency in-plane donor OH librational modes for mixed alcohol-water complexes. The vibrational assignments confirm directly that water acts as the hydrogen bond donor in the most stable mixed complexes and the tertiary alcohol is a superior hydrogen bond acceptor. The class of large-amplitude donor OH librational motion is shown to account for up to 5.1 kJ mol(-1) of the destabilizing change of vibrational zero-point energy upon intermolecular OHO hydrogen bond formation. The experimental findings are supported by complementary electronic structure calculations at the CCSD(T)-F12/aug-cc-pVTZ level of theory. PMID:26304774

  13. Covalent bonds are created by the drive of electron waves to lower their kinetic energy through expansion

    SciTech Connect

    Schmidt, Michael W.; Ruedenberg, Klaus; Ivanic, Joseph

    2014-05-28

    An analysis based on the variation principle shows that in the molecules H{sub 2}{sup +}, H{sub 2}, B{sub 2}, C{sub 2}, N{sub 2}, O{sub 2}, F{sub 2}, covalent bonding is driven by the attenuation of the kinetic energy that results from the delocalization of the electronic wave function. For molecular geometries around the equilibrium distance, two features of the wave function contribute to this delocalization: (i) Superposition of atomic orbitals extends the electronic wave function from one atom to two or more atoms; (ii) intra-atomic contraction of the atomic orbitals further increases the inter-atomic delocalization. The inter-atomic kinetic energy lowering that (perhaps counter-intuitively) is a consequence of the intra-atomic contractions drives these contractions (which per se would increase the energy). Since the contractions necessarily encompass both, the intra-atomic kinetic and potential energy changes (which add to a positive total), the fact that the intra-atomic potential energy change renders the total potential binding energy negative does not alter the fact that it is the kinetic delocalization energy that drives the bond formation.

  14. Covalent bonds are created by the drive of electron waves to lower their kinetic energy through expansion

    SciTech Connect

    Schmidt, Michael W; Ivanic, Joseph; Ruedenberg, Klaus

    2014-05-28

    An analysis based on the variation principle shows that in the molecules H2 +, H2, B2, C2, N2, O2, F2, covalent bonding is driven by the attenuation of the kinetic energy that results from the delocalization of the electronic wave function. For molecular geometries around the equilibrium distance, two features of the wave function contribute to this delocalization: (i) Superposition of atomic orbitals extends the electronic wave function from one atom to two or more atoms; (ii) intra-atomic contraction of the atomic orbitals further increases the inter-atomic delocalization. The inter-atomic kinetic energy lowering that (perhaps counter-intuitively) is a consequence of the intra-atomic contractions drives these contractions (which per se would increase the energy). Since the contractions necessarily encompass both, the intra-atomic kinetic and potential energy changes (which add to a positive total), the fact that the intra-atomic potential energy change renders the total potential binding energy negative does not alter the fact that it is the kinetic delocalization energy that drives the bond formation.

  15. Covalent bonds are created by the drive of electron waves to lower their kinetic energy through expansion

    PubMed Central

    Schmidt, Michael W.; Ivanic, Joseph; Ruedenberg, Klaus

    2014-01-01

    An analysis based on the variation principle shows that in the molecules H2+, H2, B2, C2, N2, O2, F2, covalent bonding is driven by the attenuation of the kinetic energy that results from the delocalization of the electronic wave function. For molecular geometries around the equilibrium distance, two features of the wave function contribute to this delocalization: (i) Superposition of atomic orbitals extends the electronic wave function from one atom to two or more atoms; (ii) intra-atomic contraction of the atomic orbitals further increases the inter-atomic delocalization. The inter-atomic kinetic energy lowering that (perhaps counter-intuitively) is a consequence of the intra-atomic contractions drives these contractions (which per se would increase the energy). Since the contractions necessarily encompass both, the intra-atomic kinetic and potential energy changes (which add to a positive total), the fact that the intra-atomic potential energy change renders the total potential binding energy negative does not alter the fact that it is the kinetic delocalization energy that drives the bond formation. PMID:24880263

  16. Is the decrease of the total electron energy density a covalence indicator in hydrogen and halogen bonds?

    PubMed

    Angelina, Emilio L; Duarte, Daro J R; Peruchena, Nlida M

    2013-05-01

    In this work, halogen bonding (XB) and hydrogen bonding (HB) complexes were studied with the aim of analyzing the variation of the total electronic energy density H(r b ) with the interaction strengthening. The calculations were performed at the MP2/6-311++G(2d,2p) level of approximation. To explain the nature of such interactions, the atoms in molecules theory (AIM) in conjunction with reduced variational space self-consistent field (RVS) energy decomposition analysis were carried out. Based on the local virial theorem, an equation to decompose the total electronic energy density H(r b ) in two energy densities, (-G(r b )) and 1/4?(2)?(r b ), was derived. These energy densities were linked with the RVS interaction energy components. Through the connection between both decomposition schemes, it was possible to conclude that the decrease in H(r b ) with the interaction strengthening observed in the HB as well as the XB complexes, is mainly due to the increase in the attractive electrostatic part of the interaction energy and in lesser extent to the increase in its covalent character, as is commonly considered. PMID:23187685

  17. Financing Public Sector Projects with Clean Renewable Energy Bonds; Fact Sheet Series on Financing Renewable Energy Projects, National Renewable Energy Laboratory (NREL)

    SciTech Connect

    Kreycik, C.; Couglin, J.

    2009-12-01

    Clean renewable energy bonds (CREBs) present a low-cost opportunity for public entities to issue bonds to finance renewable energy projects. The federal government lowers the cost of debt by providing a tax credit to the bondholder in lieu of interest payments from the issuer. Because CREBs are theoretically interest free, they may be more attractive than traditional tax-exempt municipal bonds. In February 2009, Congress appropriated a total of $2.4 billion for the "New CREBs" program. No more than one-third of the budget may be allocated to each of the eligible entities: governmental bodies, electric cooperatives, and public power providers. Applications for this round of "New CREBs" were due to the Internal Revenue Service (IRS) on August 4, 2009. There is no indication Congress will extend the CREBs program; thus going forward, only projects that are approved under the 2009 round will be able to issue CREBs. This factsheet explains the CREBs mechanism and provides guidance on procedures related to issuing CREBs.

  18. C-H and C-C clumping in ethane by high-resolution mass spectrometry

    NASA Astrophysics Data System (ADS)

    Clog, M. D.; Eiler, J. M.

    2014-12-01

    Ethane (C2H6) is an important natural compound, and its geochemistry can be studied through 13C-13C, 13C-D and/or D-D clumping. Such measurements are potentially important both as a stepping stone towards the study of more complex organic molecules and, in its own regard, to understand processes controlling the generation, migration and destruction of natural gas. Isotopic clumping on C-C and C-H bonds could be influenced by thermodynamics, chemical kinetics, diffusion or gas mixing. Previous work showed that 13C-D clumping in methane generally reflects equilibrium and provides a measure of formation temperature (Stolper et al 2014a), whereas 13C-13C clumping in ethane is likely most controlled by chemical-kinetic processes and/or inheritance from the isotopic structure of source organic compounds (Clog et al 2014). 13C-D clumping in ethane has the potential to provide a thermometer for its synthesis, as it does for methane. However, the difference in C-H bond dissociation energy for these two compounds may suggest a lower 'blocking temperature' for this phenomenon in ethane (the blocking temperature for methane is ?~250 C in geological conditions). We present analytical techniques to measure both 13C-13C and 13C-D clumping in ethane, using a novel two-instrument technique, including both the Thermo 253-Ultra and the Thermo DFS. In this method, the Ultra is used to measure the relative abundances of combinations nearly isobaric isotopologues: (13C12CH6 + 12C2DH5)/12C2H6 and (13C2H6 + 12C13CDH5)/12C2H6, free of other isobaric interferences like O2. The DFS, a very high resolution single-collector instrument, is then used to measure the ratios of isotopologues of ethane at a single cardinal mass: 12C2DH5/13C12CH6, and 12C13CDH5/13C2H6, with precisions of ~1 permil. Those 4 measurements allow us to calculate the bulk isotopic composition (?D and ?13C) as well as the abundance of 13C2H6 and 13C12CDH5. We also present progress on the development of software tools to use the data measured with the DFS efficiently.

  19. Impact megadomes and the origin of the martian crustal dichotomy C.C. Reese

    E-print Network

    Impact megadomes and the origin of the martian crustal dichotomy C.C. Reese , C.P. Orth, V Impact processes a b s t r a c t We show that a sufficiently energetic impact can generate a melt volume depleted mantle. Depending on impact energy and initial crustal thickness, a basin may be retained

  20. Tubulin bond energies and microtubule biomechanics determined from nanoindentation in silico

    E-print Network

    Kononova, Olga; Theisen, Kelly E; Marx, Kenneth A; Dima, Ruxandra I; Ataullakhanov, Fazly I; Grishchuk, Ekaterina L; Barsegov, Valeri

    2015-01-01

    Microtubules, the primary components of the chromosome segregation machinery, are stabilized by longitudinal and lateral non-covalent bonds between the tubulin subunits. However, the thermodynamics of these bonds and the microtubule physico-chemical properties are poorly understood. Here, we explore the biomechanics of microtubule polymers using multiscale computational modeling and nanoindentations in silico of a contiguous microtubule fragment. A close match between the simulated and experimental force-deformation spectra enabled us to correlate the microtubule biomechanics with dynamic structural transitions at the nanoscale. Our mechanical testing revealed that the compressed MT behaves as a system of rigid elements interconnected through a network of lateral and longitudinal elastic bonds. The initial regime of continuous elastic deformation of the microtubule is followed by the transition regime, during which the microtubule lattice undergoes discrete structural changes, which include first the reversib...

  1. Rotational spectrum, dynamics and bond energy of 2,5-dihydrofuran-krypton van der Waals complex

    NASA Astrophysics Data System (ADS)

    Velino, Biagio; Melandri, Sonia; Maris, Assimo; Favero, Paolo G.; Caminati, Walther

    The equilibrium conformation, dynamics and dissociation energy of the weakly bonded 2,5-dihydrofuran-Kr complex have been deduced from its free jet millimetre-wave spectrum. The equilibrium distance of Kr with respect to the centre of mass of the molecule is 3.61 , with Kr tilted 12.8o from the perpendicular to the centre of mass of the ring towards the oxygen atom. The dissociation energy is estimated from the centrifugal distortion constant DJ to be about 3.5kJ mol-1.

  2. Complexes of neon with nonaromatic ring molecules: Rotational spectrum, dynamics, and bond energy of 2,5-dihydrofuran-neon

    NASA Astrophysics Data System (ADS)

    Maris, Assimo; Favero, Paolo G.; Dell'Erba, Adele; Caminati, Walther

    1999-05-01

    The equilibrium configuration, dynamics, and dissociation energy of the very weakly bonded 2,5-dihydrofuran⋯Ne complex have been deduced from its free jet millimeter wave spectrum. The equilibrium distance of Ne with respect to the center of mass of the molecule is 3.30 , with Ne tilted 7.3 from the perpendicular to the center of mass of the ring toward the oxygen atom. The dissociation energy is estimated, from the centrifugal distortion constant DJ, to be ca. 1.1 kJ/mol.

  3. Experimental determination of the HO-Br bond energy and its relevance to the stratospheric and tropospheric ozone cycles

    SciTech Connect

    Ruscic, B.; Berkowitz, J.

    1996-02-01

    The HO-Br bond energy (and consequently the heat of formation of HOBr) has been determined experimentally for the first time. HOBr can be photolyzed in the stratosphere to form Br and OH, both of which can react with ozone, and destroy it. Previous calculations modeling stratospheric reactions have assumed a lower stability than that found in the current research. The stability of HOBr was determined by measuring the threshold for formation of Br{sup +} from this molecule, using photoionization mass spectrometry. Their work was supported by the Division of Chemical Sciences, Office of Basic Energy Sciences.

  4. Ultrasonically bonded value assembly

    NASA Technical Reports Server (NTRS)

    Salvinski, R. J. (inventor)

    1975-01-01

    A valve apparatus capable of maintaining a fluid-tight seal over a relatively long period of time by releasably bonding a valve member to its seat is described. The valve member is bonded or welded to the seat and then released by the application of the same energy to the bond joint. The valve member is held in place during the bonding by a clamping device. An appropriate force device can activate the opening and closing of the valve member. Various combinations of material for the valve member and valve seat can be utilized to provide an adequate sealing bond. Aluminum oxide, stainless steel, inconel, tungsten carbide as hard materials and copper, aluminum, titanium, silver, and gold as soft materials are suggested.

  5. Characterization of Brazed Joints of C-C Composite to Cu-clad-Molybdenum

    NASA Technical Reports Server (NTRS)

    Singh, M.; Asthana, R.

    2008-01-01

    Carbon-carbon composites with either pitch+CVI matrix or resin-derived matrix were joined to copper-clad molybdenum using two active braze alloys, Cusil-ABA (1.75% Ti) and Ticusil (4.5% Ti). The brazed joints revealed good interfacial bonding, preferential precipitation of Ti at the composite/braze interface, and a tendency toward de-lamination in resin-derived C-C composite due to its low inter-laminar shear strength. Extensive braze penetration of the inter-fiber channels in the pitch+CVI C-C composites was observed. The relatively low brazing temperatures (<950 C) precluded melting of the clad layer and restricted the redistribution of alloying elements but led to metallurgically sound composite joints. The Knoop microhardness (HK) distribution across the joint interfaces revealed sharp gradients at the Cu-clad-Mo/braze interface and higher hardness in Ticusil (approx.85-250 HK) than in Cusil-ABA (approx.50-150 HK). These C-C/Cu-clad-Mo joints with relatively low thermal resistance may be promising for thermal management applications.

  6. Effects of density functionals and dispersion interactions on geometries, bond energies and harmonic frequencies of Etbnd UX3 (E = N, P, CH; X = H, F, Cl)

    NASA Astrophysics Data System (ADS)

    Pandey, Krishna Kumar; Patidar, Pankaj; Patidar, Sunil Kumar; Vishwakarma, Ravi

    2014-12-01

    Quantum-chemical calculations have been performed to evaluate the geometries, bonding nature and harmonic frequencies of the compounds [Etbnd UX3] at DFT, DFT-D3, DFT-D3(BJ) and DFT-dDSc levels using different density functionals BP86, BLYP, PBE, revPBE, PW91, TPSS and M06-L. The stretching frequency of Utbnd N bond in [Ntbnd UF3] calculated with DFT/BLYP closely resembles with the experimental value. The performance of different density functionals for accurate Utbnd N vibrational frequencies follows the order BLYP > revPBE > BP86 > PW91 > TPSS > PBE > M06-L. The BLYP functional gives accurate value of the Utbnd E bond distances. The uranium atom in the studied compounds [Etbnd UX3] is positively charged. Upon going from [Etbnd UF3] to [Etbnd UCl3], the partial Hirshfeld charge on uranium atom decreases because of the lower electronegativity of chlorine compared to flourine. The Gopinathan-Jug bond order for Utbnd E bonds ranges from 2.90 to 3.29. The Utbnd E bond dissociation energies vary with different density functionals as M06-L < TPSS < BLYP < revPBE < BP86 < PBE ? PW91. The orbital interactions ?Eorb, in all studied compounds [Etbnd UX3] are larger than the electrostatic interaction ?Eelstat, which means the Utbnd N bonds in these compound have greater degree of covalent character (in the range 63.8-77.2%). The Usbnd E ?-bonding interaction is the dominant bonding interaction in the nitride and methylidyne complexes while it is weaker in [Ptbnd UX3]. The dispersion energy contributions to the total bond dissociation energies are rather small. Compared to the Grimme's D3(BJ) corrections, the Corminboeuf's dispersion corrections are larger with metaGGA functionals (TPSS, M06-L) while smaller with GGA functionals.

  7. Effects of density functionals and dispersion interactions on geometries, bond energies and harmonic frequencies of EUX3 (E=N, P, CH; X=H, F, Cl).

    PubMed

    Pandey, Krishna Kumar; Patidar, Pankaj; Patidar, Sunil Kumar; Vishwakarma, Ravi

    2014-12-10

    Quantum-chemical calculations have been performed to evaluate the geometries, bonding nature and harmonic frequencies of the compounds [EUX3] at DFT, DFT-D3, DFT-D3(BJ) and DFT-dDSc levels using different density functionals BP86, BLYP, PBE, revPBE, PW91, TPSS and M06-L. The stretching frequency of UN bond in [NUF3] calculated with DFT/BLYP closely resembles with the experimental value. The performance of different density functionals for accurate UN vibrational frequencies follows the order BLYP>revPBE>BP86>PW91>TPSS>PBE>M06-L. The BLYP functional gives accurate value of the UE bond distances. The uranium atom in the studied compounds [EUX3] is positively charged. Upon going from [EUF3] to [EUCl3], the partial Hirshfeld charge on uranium atom decreases because of the lower electronegativity of chlorine compared to flourine. The Gopinathan-Jug bond order for UE bonds ranges from 2.90 to 3.29. The UE bond dissociation energies vary with different density functionals as M06-Lbonds in these compound have greater degree of covalent character (in the range 63.8-77.2%). The UE ?-bonding interaction is the dominant bonding interaction in the nitride and methylidyne complexes while it is weaker in [PUX3]. The dispersion energy contributions to the total bond dissociation energies are rather small. Compared to the Grimme's D3(BJ) corrections, the Corminboeuf's dispersion corrections are larger with metaGGA functionals (TPSS, M06-L) while smaller with GGA functionals. PMID:25014545

  8. Performance and Reliability of Bonded Interfaces for High-Temperature Packaging; NREL (National Renewable Energy Laboratory)

    SciTech Connect

    DeVoto, Douglas

    2015-06-10

    This is a technical review of the DOE VTO EDT project EDT063, Performance and Reliability of Bonded Interfaces for High-Temperature Packaging. A procedure for analyzing the reliability of sintered-silver through experimental thermal cycling and crack propagation modeling has been outlined and results have been presented.

  9. Aircraft surface coatings study: Energy efficient transport program. [sprayed and adhesive bonded coatings for drag reduction

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Surface coating materials for application on transport type aircraft to reduce drag, were investigated. The investigation included two basic types of materials: spray on coatings and adhesively bonded films. A cost/benefits analysis was performed, and recommendations were made for future work toward the application of this technology.

  10. Diffusion bonding

    NASA Astrophysics Data System (ADS)

    Brown, L. E.

    1993-03-01

    A temperature between 400 and 500 and a pressure between 40 MPa and 160 MPa were indicated by a two-factor, three-level factorial experiment for diffusion bonding of molybdenum sheet substrates. These substrates were sputter ion plated with palladium (0.5 microns) and silver (10 microns) films on the mating surfaces, with the silver used as a bonding interlayer. The palladium acted as an adhesive layer between the silver film and molybdenum substrate. The silver diffusion bonds that resulted were qualitatively characterized at the interfacial regions, and bonds with no visible interface were obtained at 7500X magnification. Correlations were obtained for voids found optically at the silver/silver bonding interface and colored image maps, illustrating bond quality, produced by nondestructive ultrasonic imaging. Above 160 MPa, the bonding process produces samples with a nonuniform load distribution. These samples contained regions with gaps and well-bonded regions at the silver/silver interface, and all had macroscopic deformation of the silver films.

  11. Electrophilic, Ambiphilic, and Nucleophilic C-H bond Activation. Understanding the electronic continuum of C-H bond activation through transition-state and reaction pathway interaction energy decompositions

    SciTech Connect

    Ess, Daniel H.; Goddard, William A.; Periana, Roy A.

    2010-10-29

    The potential energy and interaction energy profiles for metal- and metal-ligand-mediated alkane C-H bond activation were explored using B3LYP density functional theory (DFT) and the absolutely localized molecular orbital energy decomposition analysis (ALMO-EDA). The set of complexes explored range from late transition metal group 10 (Pt and Pd) and group 11 (Au) metal centers to group 7-9 (Ir, Rh, Ru, and W) metal centers as well as a group 3 Sc complex. The coordination geometries, electron metal count (d8, d6, d4, and d0), and ligands (N-heterocycles, O-donor, phosphine, and Cp*) are also diverse. Quantitative analysis using ALMO-EDA of both directions of charge-transfer stabilization (occupied to unoccupied orbital stabilization) energies between the metal-ligand fragment and the coordinated C-H bond in the transition state for cleavage of the C-H bond allows classification of C-H activation reactions as electrophilic, ambiphilic, or nucleophilic on the basis of the net direction of charge-transfer energy stabilization. This bonding pattern transcends any specific mechanistic or bonding paradigm, such as oxidative addition, ?-bond metathesis, or substitution. Late transition metals such as Au(III), Pt(II), Pd(II), and Rh(III) metal centers with N-heterocycle, halide, or O-donor ligands show electrophilically dominated reaction profiles with forward charge-transfer from the C-H bond to the metal, leading to more stabilization than reverse charge transfer from the metal to the C-H bond. Transition states and reaction profiles for d6 Ru(II) and Ir(III) metals with Tp and acac ligands were found to have nearly equal forward and reverse charge-transfer energy stabilization. This ambiphilic region also includes the classically labeled electrophilic cationic species Cp*(PMe3)Ir(Me). Nucleophilic character, where the metal to C-H bond charge-transfer interaction is most stabilizing, was found in metathesis reactions with W(II) and Sc(III) metal center complexes in reactions as well as late transition metal Ir(I) and Rh(I) pincer complexes that undergo C-H bond insertion. Comparison of pincer ligands shows that the PCP ligand imparts more nucleophilic character to an Ir metal center than a deprotonated PNP ligand. The PCP and POCOP ligands do not show a substantial difference in the electronics of C-H activation. It was also found that Rh(I) is substantially more nucleophilic than Ir(I). Lastly, as a qualitative approximation, investigation of transition-state fragment orbital energies showed that relative frontier orbital energy gaps correctly reflect electrophilic, ambiphilic, or nucleophilic charge-transfer stabilization patterns.

  12. 7. Historic American Buildings Survey, C. C. Adams, Photographer August ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. Historic American Buildings Survey, C. C. Adams, Photographer August 1931, SEED PACKING ROOM, Gift of New York State Department of Education. - Shaker North Family Washhouse (first), Shaker Road, New Lebanon, Columbia County, NY

  13. Re-evaluation of the bond length-bond strength rule: The stronger bond is not always the shorter bond.

    PubMed

    Kraka, Elfi; Setiawan, Dani; Cremer, Dieter

    2016-01-01

    A set of 42 molecules with N-F, O-F, N-Cl, P-F, and As-F bonds has been investigated in the search for potential bond anomalies, which lead to reverse bond length-bond strength (BLBS) relationships. The intrinsic strength of each bond investigated has been determined by the local stretching force constant obtained at the CCSD(T)/aug-cc-pVTZ level of theory. N-F or O-F bond anomalies were found for fluoro amine radicals, fluoro amines, and fluoro oxides, respectively. A rationale for the deviation from the normal Badger-type inverse BLBS relation is given and it is shown that electron withdrawal accompanied by strong orbital contraction and bond shortening is one of the prerequisites for a bond anomaly. In the case of short electron-rich bonds such as N-F or O-F, anomeric delocalization of lone pair electrons in connection with lone pair repulsion are decisive whether a bond anomaly can be observed. This is quantitatively assessed with the help of the CCSD(T) local stretching force constants, CCSD(T) charge distributions, and G4 bond dissociation energies. Bond anomalies are not found for fluoro phosphines and fluoro arsines because the bond weakening effects are no longer decisive. 2015 Wiley Periodicals, Inc. PMID:26515027

  14. Total Synthesis of 6-Deoxyerythronolide B via C-C Bond-Forming Transfer Hydrogenation

    PubMed Central

    Gao, Xin; Woo, Sang Kook; Krische, Michael J.

    2013-01-01

    The 14-membered macrolide 6-deoxyerythronolide B is prepared in 14 steps (longest linear sequence) and 20 total steps. Two different methods for alcohol CH-crotylation via transfer hydrogenation are deployed for the first time in target-oriented synthesis. Enyne metathesis is used to form the 14-membered ring. The present approach represents the most concise construction of any erythronolide reported, to date. PMID:23464668

  15. A family of low molecular-weight, organic catalysts for reductive C-C bond formation.

    PubMed

    Shaaban, Saad; Jolit, Anas; Petkova, Desislava; Maulide, Nuno

    2015-09-21

    Hydrazines form a new family of low molecular-weight reducing agents for diazonium salts. Using only small amounts of hydrazine catalyst, the coupling of diazonium salts to a variety of reactive partners has been achieved, without the requirement for either metal adjuvants or irradiation with visible or ultraviolet light. The generality of the concept proposed herein as well as its advantages in the preparative scale is outlined and discussed. PMID:26239300

  16. Photochemically-induced C-C bond formation between tertiary amines and nitrones.

    PubMed

    Itoh, Kennosuke; Kato, Ryo; Kinugawa, Daito; Kamiya, Hideaki; Kudo, Ryuki; Hasegawa, Masayuki; Fujii, Hideaki; Suga, Hiroyuki

    2015-09-01

    Photoexcited nitrones serve as excellent electron acceptors as well as radical acceptors in the presence of tertiary amines to give ?-amino hydroxylamines via photochemically-induced direct sp(3) C-H functionalization of the tertiary amines. The combined use of an organophotosensitizer and photoirradiation was highly effective in accelerating addition reactions. Several nitrones and tertiary amines were successfully utilized to give ?-amino hydroxylamines in good yield. Highly regioselective generation of primary ?-aminoalkyl radicals based on Lewis's stereoelectronic rule and diastereoselective addition reactions of primary ?-aminoalkyl radicals with nitrones were successfully achieved. Furthermore, a highly diastereoselective reaction of an ?-aminoalkyl radical with a chiral (E)-geometry-fixed ?-alkoxycarbonylnitrone was performed. PMID:26205235

  17. Using Qualified Energy Conservation Bonds (QECBs) to Fund a Residential Energy Efficiency Loan Program: Case Study on Saint Louis County, MO

    SciTech Connect

    Zimring, Mark

    2011-06-23

    Qualified Energy Conservation Bonds (QECBs) are federally-subsidized debt instruments that enable state, tribal, and local government issuers to borrow money to fund a range of qualified energy conservation projects. QECBs offer issuers very attractive borrowing rates and long terms, and can fund low-interest energy efficiency loans for home and commercial property owners. Saint Louis County, MO recently issued over $10 million of QECBs to finance the Saint Louis County SAVES residential energy efficiency loan program. The county's experience negotiating QECB regulations and restrictions can inform future issuers.

  18. Carbon-carbon bond cleavage of 1,2-hydroxy ethers b7 vanadium(V) dipicolinate complexes

    SciTech Connect

    Hanson, Susan K; Gordon, John C; Thorn, David L; Scott, Brian L; Baker, R Tom

    2009-01-01

    The development of alternatives to current petroleum-based fuels and chemicals is becoming increasingly important due to concerns over climate change, growing world energy demand, and energy security issues. Using non-food derived biomass to produce renewable feedstocks for chemicals and fuels is a particularly attractive possibility. However, the majority of biomass is in the form of lignocellulose, which is often not fully utilized due to difficulties associated with breaking down both lignin and cellulose. Recently, a number of methods have been reported to transform cellulose directly into more valuable materials such as glucose, sorbitol, 5-(chloromethyl)furfural, and ethylene glycol. Less progress has been made with selective transformations of lignin, which is typically treated in paper and forest industries by kraft pulping (sodium hydroxide/sodium sulfide) or incineration. Our group has begun investigating aerobic oxidative C-C bond cleavage catalyzed by dipicolinate vanadium complexes, with the idea that a selective C-C cleavage reaction of this type could be used to produce valuable chemicals or intermediates from cellulose or lignin. Lignin is a randomized polymer containing methoxylated phenoxy propanol units. A number of different linkages occur naturally; one of the most prevalent is the {beta}-O-4 linkage shown in Figure 1, containing a C-C bond with 1,2-hydroxy ether substituents. While the oxidative C-C bond cleavage of 1,2-diols has been reported for a number of metals, including vanadium, iron, manganese, ruthenium, and polyoxometalate complexes, C-C bond cleavage of 1,2-hydroxy ethers is much less common. We report herein vanadium-mediated cleavage of C-C bonds between alcohol and ether functionalities in several lignin model complexes. In order to explore the scope and potential of vanadium complexes to effect oxidative C-C bond cleavage in 1,2-hydroxy ethers, we examined the reactivity of the lignin model complexes pinacol monomethyl ether (A), 2-phenoxyethanol (B), and 1,2-diphenyl-2-methoxyethanol (C) (Figure 1). Reaction of (dipic)V{sup V}(O)O{sup i}Pr (1a) or (dipic)V{sup v}(O)OEt (lb) with A, B, or C in acetonitrile yielded new vanadium(V) complexes where the alcohol-ether ligand was bound in a chelating fashion. From the reaction of 1b with pinacol monomethyl ether (A) in acetonitrile solution, (dipic)V{sup v}(O)(pinOMe) (2) (PinOMe = 2,3-dimethyl-3-methoxy-2-butanoxide) was isolated in 61 % yield. Reaction of 1b with 2-phenoxyethanol (B) in acetonitrile gave the new complex (dipic)V{sup v}(O)(OPE) (3) (OPE = 2-phenoxyethoxide), which was isolated in 76% yield. In a similar fashion, 1a reacted with 1,2-diphenyl-2-methoxyethanol (C) to give (dipic)V(O)(DPME) (4) (DPME = 1,2-diphenyl-2-methoxyethoxide), which was isolated in 39% yield. Complexes 2, 3, and 4 were characterized by {sup 1}H NMR and IR spectroscopy, elemental analysis, and X-ray crystallography. Compared to the previously reported vanadium(V) pinacolate complex (dipic)V(O)(pinOH) the X-ray structure of complex 2 reveals a slightly shorter V = O bond, 1.573(2) {angstrom} vs 1.588(2) {angstrom} for the pinOH structure. Complexes 3 and 4 display similar vanadium oxo bond distances of 1.568(2) {angstrom} and 1.576(2) {angstrom}, respectively. All three complexes show longer bonds to the ether-oxygen trans to the oxo (2.388(2) {angstrom} for 2, 2.547(2) {angstrom} for 3, and 2.438(2) {angstrom} for 4) than to the hydroxy-oxygen in the pinOH structure (2.252(2) {angstrom}).

  19. Study of dielectron production in C+C collisions at 1A GeV

    NASA Astrophysics Data System (ADS)

    Hades Collaboration; Agakishiev, G.; Agodi, C.; Alvarez-Pol, H.; Balanda, A.; Bassini, R.; Bellia, G.; Belver, D.; Belyaev, A.; Blanco, A.; Bhmer, M.; Bortolotti, A.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Daz, J.; Dohrmann, F.; Dybczak, A.; Eberl, T.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Frhlich, I.; Galatyuk, T.; Garzn, J. A.; Gernhuser, R.; Gil, A.; Gilardi, C.; Golubeva, M.; Gonzlez-Daz, D.; Grosse, E.; Guber, F.; Heilmann, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kmpfer, B.; Kajetanowicz, M.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Kozuch, A.; Krsa, A.; Krizek, F.; Krcken, R.; Khn, W.; Kugler, A.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, J. S.; Lapidus, K.; Lopes, L.; Maier, L.; Mangiarotti, A.; Marn, J.; Markert, J.; Metag, V.; Michalska, B.; Mishra, D.; Morinire, E.; Mousa, J.; Mnch, M.; Mntz, C.; Naumann, L.; Novotny, R.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Prez Cavalcanti, T.; Pietraszko, J.; Pleskac, R.; Pospsil, V.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Schroeder, C.; Schwab, E.; Simon, R. S.; Sobolev, Yu. G.; Spataro, S.; Spruck, B.; Strbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tarantola, A.; Teilab, K.; Tlusty, P.; Toia, A.; Traxler, M.; Trebacz, R.; Tsertos, H.; Veretenkin, I.; Wagner, V.; Weber, M.; Wen, H.; Wisniowski, M.; Wojcik, T.; Wstenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zhou, P.; Zumbruch, P.

    2008-05-01

    The emission of ee pairs from C+C collisions at an incident energy of 1 GeV per nucleon has been investigated. The measured production probabilities, spanning from the ?-Dalitz to the ?/? invariant-mass region, display a strong excess above the cocktail of standard hadronic sources. The bombarding-energy dependence of this excess is found to scale like pion production, rather than like eta production. The data are in good agreement with results obtained in the former DLS experiment.

  20. Testing of DLR C/C-SiC and C/C for HIFiRE 8 Scramjet Combustor

    NASA Technical Reports Server (NTRS)

    Glass, David E.; Capriotti, Diego P.; Reimer, Thomas; Kutemeyer, Marius; Smart, Michael K.

    2014-01-01

    Ceramic Matrix Composites (CMCs) have been proposed for use as lightweight hot structures in scramjet combustors. Previous studies have calculated significant weight savings by utilizing CMCs (active and passive) versus actively cooled metallic scramjet structures. Both a carbon/carbon (C/C) and a carbon/carbon-silicon carbide (C/C-SiC) material fabricated by DLR (Stuttgart, Germany) are being considered for use in a passively cooled combustor design for Hypersonic International Flight Research Experimentation (HIFiRE) 8, a joint Australia / Air Force Research Laboratory hypersonic flight program, expected to fly at Mach 7 for approximately 30 sec, at a dynamic pressure of 55 kilopascals. Flat panels of the DLR C/C and C/C-SiC materials were installed downstream of a hydrogen-fueled, dual-mode scramjet combustor and tested for several minutes at conditions simulating flight at Mach 5 and Mach 6. Gaseous hydrogen fuel was used to fuel the scramjet combustor. The test panels were instrumented with embedded Type K and Type S thermocouples. Zirconia felt insulation was used during some of the tests to reduce heat loss from the back surface and thus increase the heated surface temperature of the C/C-SiC panel approximately 177 C (350 F). The final C/C-SiC panel was tested for three cycles totaling over 135 sec at Mach 6 enthalpy. Slightly more erosion was observed on the C/C panel than the C/C-SiC panels, but both material systems demonstrated acceptable recession performance for the HIFiRE 8 flight.

  1. Accurate energies of hydrogen bonded nucleic acid base pairs and triplets in tRNA tertiary interactions

    PubMed Central

    2006-01-01

    Tertiary interactions are crucial in maintaining the tRNA structure and functionality. We used a combined sequence analysis and quantum mechanics approach to calculate accurate energies of the most frequent tRNA tertiary base pairing interactions. Our analysis indicates that six out of the nine classical tertiary interactions are held in place mainly by H-bonds between the bases. In the remaining three cases other effects have to be considered. Tertiary base pairing interaction energies range from ?8 to ?38 kcal/mol in yeast tRNAPhe and are estimated to contribute roughly 25% of the overall tRNA base pairing interaction energy. Six analyzed posttranslational chemical modifications were shown to have minor effect on the geometry of the tertiary interactions. Modifications that introduce a positive charge strongly stabilize the corresponding tertiary interactions. Non-additive effects contribute to the stability of base triplets. PMID:16461956

  2. High-Resolution Photoelectron Spectroscopic Study of Cyclopropene (c-C_3H_4)

    NASA Astrophysics Data System (ADS)

    Vasilatou, Konstantina; Michaud, Julie M.; Grassi, Guido; Baykusheva, Denitsa; Merkt, Frederic

    2012-06-01

    The spectroscopic information available on the cyclopropene radical cation is limited to that contained in low-resolution He I photoelectron spectra. To better characterize the structure of this cation, we have recently measured high-resolution PFI-ZEKE photoelectron spectra of c-C_3H_4 and several of its deuterated isotopomers in the vicinity of the adiabatic ionization threshold. Our new data include fully rotationally resolved spectra of the origin band of the widetilde{X}^+?widetilde{X} transition of c-C_3H_4 and spectra of the low-vibrational levels of c-C_3H_4 and the deuterated isotopomers recorded at lower resolution. Because our efforts at synthesizing the partially deuterated isotopomers always resulted in mixtures of several isotopomers, differing in their number of D atoms and in the location of these atoms, the analysis of the isotopic shifts turned out to be challenging. Combining the information contained in the rotational structure of the origin band of c-C_3H_4 with the ionization energies of the isotopomers measured by photoionization mass spectrometry and the vibrational structure observed in the PFI-ZEKE spectra of the mixtures of deuterated isotopomers, we were able to draw conclusions on the structure of the cyclopropene radical cation based solely on experimental data. The adiabatic ionization energy of c-C_3H_4 was determined to be 77931.8(5) {cm}-1. M. B. Robin, C. R. Brundle, N. A. Kuebler, G. B. Ellison and K. B. Wiberg, J. Chem. Phys. 57, 1758 (1972). P. Bischof and E. Heilbronner, Helv. Chim. Acta 53, 1677 (1970).

  3. Homogeneous Gold Catalysis Highly Efficient Functionalization of CC Multiple Bonds and Electron-Rich CH Bonds

    E-print Network

    Stoltz, Brian M.

    Homogeneous Gold Catalysis Highly Efficient Functionalization of CC Multiple Bonds and Electron references: Puddephatt, R. The Chemistry of Gold; E. L. Sevier Scientific Publication Co., Amsterdam, 1978. Hashmi, A. S. K. Gold Bulletin 2004, 37, 51-65. Parish, R. V. Gold Bulletin 1997, 30, 3-12. Parish, R. V

  4. Influence of Ti nanocrystallization on microstructure, interface bonding, surface energy and blood compatibility of surface TiO 2 films

    NASA Astrophysics Data System (ADS)

    Shao, Honghong; Yu, Chunhang; Xu, Xiaojing; Wang, Ji; Zhai, Rui; Wang, Xiaojing

    2010-12-01

    Recent progress in ultrafine-grained/nano-grained (UFG/NG) titanium permits a consideration for TiO 2 films deposited on nano-grained titanium for antithrombogenic application such as artificial valves and stents. For this paper, the microstructure, interface bonding, surface energy, and blood compatibility features of TiO 2 films deposited by direct current magnetron reactive sputtering technology on NG titanium and coarse-grained (CG) titanium were investigated. The results show that the nanocrystallization of titanium substrate has a significant influence on TiO 2 films. At the same deposition parameters, the content of rutile phase of TiO 2 film was increased from 47% (on the CG titanium substrate) to 72% (on the NG titanium substrate); the adhesion of TiO 2 film was improved from 5.8 N to 17 N; the surface energy was reduced from 6.37 dyn/cm to 3.01 dyn/cm; the clotting time was improved from 18 min to 28 min; the platelets accumulation and pseudopodium of adherent platelets on TiO 2 film on NG titanium were considerably reduced compared to that on CG titanium. The present results demonstrate the possibility of improving the blood compatibility of TiO 2 film through the approach of substrate nanocrystallization. Also it may provide an attractive idea to prepare stents with biological coatings of more outstanding blood compatibility and interface bonding.

  5. Strength of Chemical Bonds

    NASA Technical Reports Server (NTRS)

    Christian, Jerry D.

    1973-01-01

    Students are not generally made aware of the extraordinary magnitude of the strengths of chemical bonds in terms of the forces required to pull them apart. Molecular bonds are usually considered in terms of the energies required to break them, and we are not astonished at the values encountered. For example, the Cl2 bond energy, 57.00 kcal/mole, amounts to only 9.46 x 10(sup -20) cal/molecule, a very small amount of energy, indeed, and impossible to measure directly. However, the forces involved in realizing the energy when breaking the bond operate over a very small distance, only 2.94 A, and, thus, f(sub ave) approx. equals De/(r - r(sub e)) must be very large. The forces involved in dissociating the molecule are discussed in the following. In consideration of average forces, the molecule shall be assumed arbitrarily to be dissociated when the atoms are far enough separated so that the potential, relative to that of the infinitely separated atoms, is reduced by 99.5% from the potential of the molecule at the equilibrium bond length (r(sub e)) for Cl2 of 1.988 A this occurs at 4.928 A.

  6. Bond Dissociation Energies of the Tungsten Fluorides and Their Singly-Charged Ions: A Density Functional Survey

    NASA Technical Reports Server (NTRS)

    Dyall, Kenneth G.; Arnold, James (Technical Monitor)

    1999-01-01

    The dissociation of WF6 and the related singly-charged cations and anions into the lower fluorides and fluorine atoms has been investigated theoretically using density functional theory (B3LYP) and relativistic effective core potentials, with estimates of spin-orbit effects included using a simple model. The inclusion of spin-orbit is essential for a correct description of the thermochemistry. The total atomization energy of the neutral and anionic WF6 is reproduced to within 25 kcal/mol, but comparison of individual bond dissociation energies with available experimental data shows discrepancies of up to 10 kcal/mol. The results are nevertheless useful to help resolve discrepancies in experimental data and provide estimates of missing data.

  7. Probing the range of applicability of structure- and energy-adjusted QM/MM link bonds.

    PubMed

    Hitzenberger, Manuel; Hofer, Thomas S

    2015-10-01

    The hydrogen-capping method is one of the most popular and widely used coupling-schemes for quantum mechanics/molecular mechanics (QM/MM)-molecular dynamics simulations of macromolecular systems. This is mostly due to the fact that it is fairly convenient to implement and parametrize, thus providing an excellent compromise between accuracy and computational effort. In this work, a viable and straight-forward approach to optimize the placing of the link atom on a suitable distance ratio between the frontier atoms is discussed. To further increase the accuracy, instead of global parameters for all amino acids, different parameter sets for each type of amino acid are derived. The dependency of the link bond parameters on the chemical environment and the used QM-method is probed to assess the range of applicability of the parametrization. Suitable sets of parameters for RI-MP2, B3LYP, (RI)-B3LYP-D3, and RI-BLYP-D3 at triple-zeta level for all relevant proteinogenic amino acids are presented. Furthermore, the scope and range of the perturbation, stemming from the introduction of link bonds is evaluated through application of the presented QM/MM scheme in calculations of the active site of 15S-lipoxygenase. PMID:26235898

  8. On the Enthalpy of Formation of Hydroxyl Radical and Gas-Phase Bond Dissociation Energies of Water and Hydroxyl

    SciTech Connect

    Ruscic, Branko; Wagner, Albert F.; Harding, Lawerence B.; Asher, Robert L.; Feller, David F. ); Dixon, David A. ); Peterson, Kirk A.; Song, Yang; Qian, Ximei; Ng, C Y.; Liu, Jianbo; Wenwu, Chen

    2001-12-01

    Several photoionization experiments utilizing the positive ion cycle to derive the O-H bond energy converge to a consensus value of AE0(OH+/H2O)= 146117? 24 cm-1 (18.1162? 0.0030 eV). With the most accurate currently available ZEKE value. IE(OH)= 104989? 2 cm-1, corroborated by a number of photoelectron measurements,Error! Bookmark not defined.,Error! Bookmark not defined.,Error! Bookmark not defined.,Error! Bookmark not defined. this leads to D0(H?OH)= 41128? 24 cm-1= 117.59? 0.07 kcal/mol. This corresponds to DHf 0(OH)= 8.85? 0.07 kcal/mol, and implies D0(OH)= 35593? 24 cm-1= 101.76? 0.07 kcal/mol. The most sophisticated theoretical calculations performed so far on the HxO system, CCSD(T)/aug-cc-pVnZ, n=Q, 5, 6, and 7, extrapolated to the CBS limit and including corrections for core-valence effects, scalar relativistic effects, incomplete correlation recovery, and diagonal Born-Oppenheimer corrections reproduce the experimental results to within 0.0 - 0.2 k cal/mol. The new values of the two successive bond dissociation energies of water supersede the previously accepted values,Error! Bookmark not defined.,Error! Bookmark not defined. which were based on spectroscopic determinationsError! Bookmark not defined.,Error! Bookmark not defined. of D0(OH) using a very short Birge-Sponer extrapolation on OH/OD A1S+. An exhaustive analysis of the latter approach, combined with the application of the same procedure on a calculated potential energy curve for the state in question, demonstrates that the Birge-Sponer extrapolation underestimates the bond dissociation energy, in spite of the fact that only the last vibrational level was not observed experimentally. The new values affect a large number of other thermochemical quantities which directly or indirectly rely on or refer to D0(H-OH), D0(OH), or DHf?(OH).

  9. Pressure-driven variations of hydrogen bonding energy in ammonium azide (NH4N3): IR absorption and Raman scattering studies

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoxin; Ma, Fengxian; Ma, Chunli; Cui, Hang; Liu, Zhenxian; Zhu, Hongyang; Wang, Xiaoli; Cui, Qiliang

    2014-07-01

    In this study, high pressure infrared (IR) absorption and Raman scattering studies for ammonium azide (NH4N3) were carried out at room temperature up to 20 GPa and 22 GPa, respectively. For comparison and further assignment, the vibrational spectra at ambient conditions were calculated using CASTEP code, particularly for the far- and mid-IR modes. The recorded vibrational data consistently indicated a pressure-induced phase transition at 2.9 GPa. All observed vibrational modes maintained their identities at the high pressure phase, indicating that NH4N3 was still presented in the form of ammonium cations and azide anions linked by the hydrogen bond (N-H⋯N). Above 2.9 GPa, the relative magnitude of the torsional mode weakened and the N-H symmetric stretch displayed a redshift, indicating strengthened hydrogen bonding energy. The opposite effects were observed above 12 GPa, where the relative magnitude of the torsional mode strengthened and the N-H symmetric stretch reverted to a blueshift, indicating weakened hydrogen bonding energy. It can be concluded that the hydrogen bonding energy exhibited a weakening (0-2.9 GPa), strengthening (2.9-12 GPa), and then again weakening (12-22 GPa) phenomena with the increasing of compression. The hydrogen bonding energy changing with the increase of pressure can be ascribed to a phase transition at 2.9 GPa and a rotational or bending behavior of azide ions at 12 GPa.

  10. Pressure-driven variations of hydrogen bonding energy in ammonium azide (NH4N3): IR absorption and Raman scattering studies.

    PubMed

    Wu, Xiaoxin; Ma, Fengxian; Ma, Chunli; Cui, Hang; Liu, Zhenxian; Zhu, Hongyang; Wang, Xiaoli; Cui, Qiliang

    2014-07-14

    In this study, high pressure infrared (IR) absorption and Raman scattering studies for ammonium azide (NH4N3) were carried out at room temperature up to 20 GPa and 22 GPa, respectively. For comparison and further assignment, the vibrational spectra at ambient conditions were calculated using CASTEP code, particularly for the far- and mid-IR modes. The recorded vibrational data consistently indicated a pressure-induced phase transition at 2.9 GPa. All observed vibrational modes maintained their identities at the high pressure phase, indicating that NH4N3 was still presented in the form of ammonium cations and azide anions linked by the hydrogen bond (N-H?N). Above 2.9 GPa, the relative magnitude of the torsional mode weakened and the N-H symmetric stretch displayed a redshift, indicating strengthened hydrogen bonding energy. The opposite effects were observed above 12 GPa, where the relative magnitude of the torsional mode strengthened and the N-H symmetric stretch reverted to a blueshift, indicating weakened hydrogen bonding energy. It can be concluded that the hydrogen bonding energy exhibited a weakening (0-2.9 GPa), strengthening (2.9-12 GPa), and then again weakening (12-22 GPa) phenomena with the increasing of compression. The hydrogen bonding energy changing with the increase of pressure can be ascribed to a phase transition at 2.9 GPa and a rotational or bending behavior of azide ions at 12 GPa. PMID:25028034

  11. Water's Hydrogen Bond Strength

    E-print Network

    Martin Chaplin

    2007-06-10

    Water is necessary both for the evolution of life and its continuance. It possesses particular properties that cannot be found in other materials and that are required for life-giving processes. These properties are brought about by the hydrogen bonded environment particularly evident in liquid water. Each liquid water molecule is involved in about four hydrogen bonds with strengths considerably less than covalent bonds but considerably greater than the natural thermal energy. These hydrogen bonds are roughly tetrahedrally arranged such that when strongly formed the local clustering expands, decreasing the density. Such low density structuring naturally occurs at low and supercooled temperatures and gives rise to many physical and chemical properties that evidence the particular uniqueness of liquid water. If aqueous hydrogen bonds were actually somewhat stronger then water would behave similar to a glass, whereas if they were weaker then water would be a gas and only exist as a liquid at sub-zero temperatures. The overall conclusion of this investigation is that water's hydrogen bond strength is poised centrally within a narrow window of its suitability for life.

  12. Adsorption of Water Monomer and Clusters on Platinum(111) Terrace and Related Steps and Kinks I. Configurations, Energies, and Hydrogen Bonding

    SciTech Connect

    Arnadottir, Liney; Stuve, Eric M.; Jonsson, Hannes

    2010-10-01

    Adsorption and rotation of water monomer, dimer, and trimer on the (111) terrace, (221) and (322) stepped, and (763) and (854) kinked surfaces of platinum were studied by density functional theory calculations using the PW91 approximation to the energy functional. On the (111) terrace, water monomer and the donor molecule of the dimer and trimer adsorb at atop sites. The permolecule adsorption energies of the monomer, dimer, and trimer are 0.30, 0.45, and 0.48 eV, respectively. Rotation of monomers, dimers, and trimers on the terrace is facile with energy barriers of 0.02 eV or less. Adsorption on steps and kinks is stronger than on the terrace, as evidenced by monomer adsorption energies of 0.46 to 0.55 eV. On the (221) stepped surface the zigzag extended configuration is most stable with a per-molecule adsorption energy of 0.57 eV. On the (322) stepped surface the dimer, two configurations of the trimer, and the zigzag configuration have similar adsorption energies of 0.55 0.02 eV. Hydrogen bonding is strongest in the dimer and trimer adsorbed on the terrace, with respective energies of 0.30 and 0.27 eV, and accounts for their increased adsorption energies relative to the monomer. Hydrogen bonding is weak to moderate for adsorption at steps, with energies of 0.04 to 0.15 eV, as the much stronger water-metal interactions inhibit adsorption geometries favorable to hydrogen bonding. Correlations of hydrogen bond angles and energies with hydrogen bond lengths are presented. On the basis of these DFT/PW91 results, a model for water cluster formation on the Pt(111) surface can be formulated where kink sites nucleate chains along the top of step edges, consistent with the experimental findings of Morgenstern et al., Phys. Rev. Lett., 77 (1996) 703.

  13. Atomistic bond relaxation, energy entrapment, and electron polarization of the RbN and CsN clusters (N ? 58).

    PubMed

    Guo, Yongling; Bo, Maolin; Wang, Yan; Liu, Yonghui; Huang, Yongli; Sun, Chang Q

    2015-11-11

    We systematically examined the effect of atomic undercoordination on the performance of bonds and electrons of Rb and Cs atomic clusters and their solid skins using a combination of photoelectron spectrometric analysis and density functional theory calculations. Results show that atomic coordination number reduction shortens the bonds by up to 30% for the Rb13 and Cs13 clusters, which densifies the local electrons and entraps their binding energies. Consistency between predictions and observations revealed that the Rb 4p level shifts from 13.654 eV for an isolated atom to a bulk value of 14.940 eV and the Cs 5p level shifts from 10.284 to 11.830 eV upon bulk formation. Such core-electron densification and entrapment polarize the valence charge from the inner to the outermost layer of skins, which perturbs the local Hamiltonian and hence dictates the unusual behavior of the Rb and Cs solid skins and nanocrystals. PMID:26507096

  14. Unexpected interplay of bonding height and energy level alignment at heteromolecular hybrid interfaces.

    PubMed

    Stadtmller, Benjamin; Lftner, Daniel; Willenbockel, Martin; Reinisch, Eva M; Sueyoshi, Tomoki; Koller, Georg; Soubatch, Serguei; Ramsey, Michael G; Puschnig, Peter; Tautz, F Stefan; Kumpf, Christian

    2014-01-01

    Although geometric and electronic properties of any physical or chemical system are always mutually coupled by the rules of quantum mechanics, counterintuitive coincidences between the two are sometimes observed. The coadsorption of the organic molecules 3,4,9,10-perylene tetracarboxylic dianhydride and copper-II-phthalocyanine on Ag(111) represents such a case, since geometric and electronic structures appear to be decoupled: one molecule moves away from the substrate while its electronic structure indicates a stronger chemical interaction, and vice versa for the other. Our comprehensive experimental and ab-initio theoretical study reveals that, mediated by the metal surface, both species mutually amplify their charge-donating and -accepting characters, respectively. This resolves the apparent paradox, and demonstrates with exceptional clarity how geometric and electronic bonding parameters are intertwined at metal-organic interfaces. PMID:24739211

  15. Substituent Effects in CH Hydrogen Bond Interactions: Linear Free Energy Relationships and Influence of Anions.

    PubMed

    Tresca, Blakely W; Hansen, Ryan J; Chau, Calvin V; Hay, Benjamin P; Zakharov, Lev N; Haley, Michael M; Johnson, Darren W

    2015-12-01

    Aryl CH hydrogen bonds (HBs) are now commonly recognized as important factors in a number of fields, including molecular biology, stereoselective catalysis, and anion supramolecular chemistry. As the utility of CH HBs has grown, so to has the need to understand the structure-activity relationship for tuning both their strength and selectivity. Although there has been significant computational effort in this area, an experimental study of the substituent effects on CH HBs has not been previously undertaken. Herein we disclose a systematic study of a single CH HB by using traditional urea donors as directing groups in a supramolecular binding cavity. Experimentally determined association constants are examined by a combination of computational (electrostatic potential) and empirical (?m and ?p) values for substituent effects. The dominance of electrostatic parameters, as observed in a computational DFT study, is consistent with current CH HB theory; however, a novel anion dependence of the substituent effects is revealed in solution. PMID:26539974

  16. The Turbulent Alfvenic Aurora C. C. Chaston,1

    E-print Network

    Bonnell, John W.

    The Turbulent Alfvenic Aurora C. C. Chaston,1 C. Salem,1 J. W. Bonnell,1 C. W. Carlson,1 R. E) It is demonstrated from observations that the Alfvenic aurora may be powered by a turbulent cascade transverse acceleration of electrons from near-Earth space to form the aurora. We find that regions of Alfven wave

  17. FROM EUCLID TO ENTROPY C. C. Rodr'iguez

    E-print Network

    Rodriguez, Carlos

    FROM EUCLID TO ENTROPY C. C. Rodr'iguez Department of Mathematics and Statistics SUNY at Albany of geometry goes something like this... Once upon a time there was a greek man named Euclid who organized the mathematical knowledge in his time in six books known as The Elements. Euclid's work was so influential

  18. Mit Methanol iridiumkatalysiert C-C-Bindungen knpfen

    E-print Network

    Meyer, Karsten

    Mit Methanol iridiumkatalysiert C-C-Bindungen knpfen i Die Reaktivitt von Methanol (1) beruht meist auf dem nucleophilen Sauerstoffatom. Obwohl Methanol industriell im Monsanto-Prozess carbo, dass Methanol iridiumkatalysiert leicht an Allene (2) addiert. Damit entstehen 2,2-disub- stituierte

  19. Optical conductivity of nodal metals C. C. Homes1

    E-print Network

    Johnson, Peter D.

    Optical conductivity of nodal metals C. C. Homes1 , J. J. Tu2 , J. Li2 , G. D. Gu1 & A. Akrap3 1 than the scattering rate, the optical conductivity adopts the well-known power law behavior s1(v) / v22-law behavior in the residual optical conductivity now permits the removal of this contribution, revealing

  20. The Gas Leakage Analysis in C/C Composites

    NASA Astrophysics Data System (ADS)

    Nishiyama, Yuichi; Hatta, Hiroshi; Bando, Takamasa; Sugibayashi, Toshio

    Gas leakage through carbon fiber reinforcement carbon composites, C/Cs, was discussed so as to apply C/Cs to heat exchangers in an engine system for a future space-plane. Since C/Cs include many cracks and pores, gas easily leaks through C/Cs. To predict and to prevent the gas flow through a C/C, leakage rate was measured as a function of pressure and gas flow path was identified by micro-observation of the C/C. Then, several analytical models were examined to clarify principal mechanism yielding gas flow resistance. It was found that laminar flow models gave far small flow resistance compared with experimental results, but a model based on adiabatic expansion and compression flow, used for gas leak through labyrinth seals, resulted in reasonable agreement. Finally, Si impregnation in a C/C was examined to minimize the gas leakage. This treatment was shown to be an excellent measure to reduce the gas leakage through C/C.

  1. Ionospheric erosion by Alfven waves C. C. Chaston,1

    E-print Network

    Bonnell, John W.

    Ionospheric erosion by Alfven waves C. C. Chaston,1 V. Genot,2 J. W. Bonnell,1 C. W. Carlson,1 J oval showing the erosion of ionospheric plasmas from the topside ionosphere by the action of Alfve), Ionospheric erosion by Alfven waves, J. Geophys. Res., 111, A03206, doi:10.1029/2005JA011367. 1. Introduction

  2. Quantification of C?C and C?O Surface Carbons in Detonation Nanodiamond by NMR

    SciTech Connect

    Cui, J -F; Fang, X -W; Schmidt-Rohr, K

    2014-05-08

    The ability of solid-state 13C NMR to detect and quantify small amounts of sp2-hybridized carbon on the surface of ?5 nm diameter nanodiamond particles is demonstrated. The C?C carbon fraction is only 1.1 0.4% in pristine purified detonation nanodiamond, while a full single-layer graphitic or bucky diamond shell would contain ca. 25% of all C in a 5 nm diameter particle. Instead of large aromatic patches repeatedly proposed in the recent literature, sp3-hybridized CH and COH carbons cover most of the nanodiamond particle surface, accounting for ?5% each. C?O and COO groups also seen in X-ray absorption near-edge structure spectroscopy (XANES) but not detected in previous NMR studies make up ca. 1.5% of all C. They are removed by heat treatment at 800 C, which increases the aromatic fraction. 13C{1H} NMR demonstrates that the various sp2-hybridized carbons are mostly not protonated, but cross-polarization shows that they are separated from 1H by only a few bond lengths, which proves that they are near the protonated surface. Together, the observed CH, COH, C?O, and C?C groups account for 1214% of all C, which matches the surface fraction expected for bulk-terminated 5 nm diameter diamond particles.

  3. Theoretical study of the C-H bond dissociation energies of CH4, C2H2, C2H4, and H2C2O

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.

    1991-01-01

    The successive C-H bond dissociation energies of CH4, C2H2, C2H4, and H2C2O (ketene) are determined using large-basis sets and a high level of correlation treatment. For CH4, C2H2, and C2H4 the computed values are in excellent agreement with experiment. Using these results, the values 107.9 + or - 2.0 and 96.7 + or - 2.0 kcal/mol are recommended for the C-H bond dissociation energies of H2C2O and HC2O, respectively.

  4. Amino Acid Mean Excitation Energies and Directional Dependencies from Core and Bond Calculations

    SciTech Connect

    Sabin, John R.; Oddershede, Jens; Sauer, Stephan P. A.

    2008-12-08

    We determine the mean excitation energies of several amino acids using a Bragg Rule developed for molecular fragments or functional groups. As the composition of the amino acids is very similar, we find that the amino acids have similar mean excitation energies (approximately 70 eV). Differences arise from variation of the side chains (-R); addition of-CH2-groups decreases the mean excitation energy. We also speculate concerning the directional dependence of the amino acid mean excitation energies.

  5. A Simple Test to Determine the Effectiveness of Different Braze Compositions for Joining Ti-Tubes to C/C Composite Plates

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Singh, Mrityunjay; Shpargel, Tarah; Asthana, Rajiv

    2006-01-01

    A simple tube-plate joint tensile test was implemented to compare the effectiveness of commercial brazes, namely, TiCuNi, TiCuSil, and Cu-ABA, used for bonding Ti-tubes joined to C-C composite plates. The different braze systems yielded different; yet, repeatable results. The Cu-ABA system proved to have about twice the load-carrying ability of the other two systems due to the fact that the bonded area between the braze material and the C-C plate was largest for this system. The orientation of the surface fiber tows also had a significant effect on load-carrying ability with tows oriented perpendicular to the tube axis displaying the highest failure loads. Increasing the process load and modifying the surface of the C-C plate by grooving out channels for the Ti-Tube to nest in resulted in increased load-carrying ability for the TiCuSil and Cu-ABA systems due to increased bonded area and better penetration of the braze material into the C-C composite.

  6. Free Energy Landscapes for S-H Bonds in (Cp2Mo2S4)-Mo-star Complexes

    SciTech Connect

    Appel, Aaron M.; Lee, Suh-Jane; Franz, James A.; DuBois, Daniel L.; Rakowski DuBois, Mary

    2009-03-23

    Extensive thermochemical data have been determined for a series of complexes derived from Cp*Mo(? S)2(? SMe)(? SH)MoCp* and Cp*Mo(? S)2(? SH)2MoCp*. These data include electrochemical potentials, pKa values, homolytic solution bond dissociation free energies (SBDFEs), and hydride donor abilities in acetonitrile. Thermochemical data ranged from +0.6 to -2.0 V vs FeCp2+/o for electrochemical potentials, 5 to 31 for pKa values, 43 to 68 kcal/mol for homolytic SBDFEs, and 44 to 84 kcal/mol for hydride donor abilities. The observed values for these thermodynamic parameters are comparable to those of many transition metal hydrides, which is consistent with the many parallels in the chemistry of these two classes of compounds. The wealth of thermochemical data are presented in free energy landscapes as a useful approach to visualizing and understanding the relative stabilities of all of the species under specified conditions. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for DOE.

  7. Clarifying Chemical Bonding. Overcoming Our Misconceptions.

    ERIC Educational Resources Information Center

    Hapkiewicz, Annis

    1991-01-01

    Demonstrations to help students change their misconceptions about chemical bond breaking are presented. Students' misconceptions about chemical bonds in both biological and chemical systems are discussed. A calculation for the release of energy from respiration is presented. (KR)

  8. 25 CFR 225.30 - Bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...30 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS OIL AND GAS, GEOTHERMAL, AND SOLID MINERALS AGREEMENTS Minerals Agreements 225.30 Bonds. (a) Bonds required by provisions of a...

  9. Photochemical tissue bonding

    DOEpatents

    Redmond, Robert W. (Brookline, MA); Kochevar, Irene E. (Charlestown, MA)

    2012-01-10

    Photochemical tissue bonding methods include the application of a photosensitizer to a tissue and/or tissue graft, followed by irradiation with electromagnetic energy to produce a tissue seal. The methods are useful for tissue adhesion, such as in wound closure, tissue grafting, skin grafting, musculoskeletal tissue repair, ligament or tendon repair and corneal repair.

  10. Low energy electron induced cytosine base release in 2?-deoxycytidine-3?-monophosphate via glycosidic bond cleavage: A time-dependent wavepacket study

    SciTech Connect

    Bhaskaran, Renjith; Sarma, Manabendra

    2014-09-14

    Low energy electron (LEE) induced cytosine base release in a selected pyrimidine nucleotide, viz., 2?-deoxycytidine-3?-monophosphate is investigated using ab initio electronic structure methods and time dependent quantum mechanical calculations. It has been noted that the cytosine base scission is comparatively difficult process than the 3? CO bond cleavage from the lowest ?{sup *} shape resonance in energy region <1 eV. This is mainly due to the high activation energy barrier associated with the electron transfer from the ?{sup *} orbital of the base to the ?{sup *} orbital of the glycosidic NC bond. In addition, the metastable state formed after impinging LEE (01 eV) has very short lifetime (10 fs) which may decay in either of the two competing auto-detachment or dissociation process simultaneously. On the other hand, the selected NC mode may cleave to form the cytosine base anion at higher energy regions (>2 eV) via tunneling of the glycosidic bond. Resonance states generated within this energy regime will exist for a duration of ?3555 fs. Comparison of salient features of the two dissociation events, i.e., 3? CO single strand break and glycosidic NC bond cleavage in 3?-dCMPH molecule are also provided.

  11. Low energy electron induced cytosine base release in 2'-deoxycytidine-3'-monophosphate via glycosidic bond cleavage: A time-dependent wavepacket study

    NASA Astrophysics Data System (ADS)

    Bhaskaran, Renjith; Sarma, Manabendra

    2014-09-01

    Low energy electron (LEE) induced cytosine base release in a selected pyrimidine nucleotide, viz., 2'-deoxycytidine-3'-monophosphate is investigated using ab initio electronic structure methods and time dependent quantum mechanical calculations. It has been noted that the cytosine base scission is comparatively difficult process than the 3' C-O bond cleavage from the lowest ?* shape resonance in energy region <1 eV. This is mainly due to the high activation energy barrier associated with the electron transfer from the ?* orbital of the base to the ?* orbital of the glycosidic N-C bond. In addition, the metastable state formed after impinging LEE (0-1 eV) has very short lifetime (10 fs) which may decay in either of the two competing auto-detachment or dissociation process simultaneously. On the other hand, the selected N-C mode may cleave to form the cytosine base anion at higher energy regions (>2 eV) via tunneling of the glycosidic bond. Resonance states generated within this energy regime will exist for a duration of 35-55 fs. Comparison of salient features of the two dissociation events, i.e., 3' C-O single strand break and glycosidic N-C bond cleavage in 3'-dCMPH molecule are also provided.

  12. Microwave bonding of MEMS component

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B. (Inventor); Mai, John D. (Inventor); Jackson, Henry W. (Inventor); Budraa, Nasser K. (Inventor); Pike, William T. (Inventor)

    2005-01-01

    Bonding of MEMs materials is carried out using microwave. High microwave absorbing films are placed within a microwave cavity, and excited to cause selective heating in the skin of the material. This causes heating in one place more than another. Thereby minimizing the effects of the bonding microwave energy.

  13. Size-extensivity-corrected multireference configuration interaction schemes to accurately predict bond dissociation energies of oxygenated hydrocarbons

    SciTech Connect

    Oyeyemi, Victor B.; Krisiloff, David B.; Keith, John A.; Libisch, Florian; Pavone, Michele; Carter, Emily A.

    2014-01-28

    Oxygenated hydrocarbons play important roles in combustion science as renewable fuels and additives, but many details about their combustion chemistry remain poorly understood. Although many methods exist for computing accurate electronic energies of molecules at equilibrium geometries, a consistent description of entire combustion reaction potential energy surfaces (PESs) requires multireference correlated wavefunction theories. Here we use bond dissociation energies (BDEs) as a foundational metric to benchmark methods based on multireference configuration interaction (MRCI) for several classes of oxygenated compounds (alcohols, aldehydes, carboxylic acids, and methyl esters). We compare results from multireference singles and doubles configuration interaction to those utilizing a posteriori and a priori size-extensivity corrections, benchmarked against experiment and coupled cluster theory. We demonstrate that size-extensivity corrections are necessary for chemically accurate BDE predictions even in relatively small molecules and furnish examples of unphysical BDE predictions resulting from using too-small orbital active spaces. We also outline the specific challenges in using MRCI methods for carbonyl-containing compounds. The resulting complete basis set extrapolated, size-extensivity-corrected MRCI scheme produces BDEs generally accurate to within 1 kcal/mol, laying the foundation for this scheme's use on larger molecules and for more complex regions of combustion PESs.

  14. Size-extensivity-corrected multireference configuration interaction schemes to accurately predict bond dissociation energies of oxygenated hydrocarbons.

    PubMed

    Oyeyemi, Victor B; Krisiloff, David B; Keith, John A; Libisch, Florian; Pavone, Michele; Carter, Emily A

    2014-01-28

    Oxygenated hydrocarbons play important roles in combustion science as renewable fuels and additives, but many details about their combustion chemistry remain poorly understood. Although many methods exist for computing accurate electronic energies of molecules at equilibrium geometries, a consistent description of entire combustion reaction potential energy surfaces (PESs) requires multireference correlated wavefunction theories. Here we use bond dissociation energies (BDEs) as a foundational metric to benchmark methods based on multireference configuration interaction (MRCI) for several classes of oxygenated compounds (alcohols, aldehydes, carboxylic acids, and methyl esters). We compare results from multireference singles and doubles configuration interaction to those utilizing a posteriori and a priori size-extensivity corrections, benchmarked against experiment and coupled cluster theory. We demonstrate that size-extensivity corrections are necessary for chemically accurate BDE predictions even in relatively small molecules and furnish examples of unphysical BDE predictions resulting from using too-small orbital active spaces. We also outline the specific challenges in using MRCI methods for carbonyl-containing compounds. The resulting complete basis set extrapolated, size-extensivity-corrected MRCI scheme produces BDEs generally accurate to within 1 kcal/mol, laying the foundation for this scheme's use on larger molecules and for more complex regions of combustion PESs. PMID:25669533

  15. Size-extensivity-corrected multireference configuration interaction schemes to accurately predict bond dissociation energies of oxygenated hydrocarbons

    NASA Astrophysics Data System (ADS)

    Oyeyemi, Victor B.; Krisiloff, David B.; Keith, John A.; Libisch, Florian; Pavone, Michele; Carter, Emily A.

    2014-01-01

    Oxygenated hydrocarbons play important roles in combustion science as renewable fuels and additives, but many details about their combustion chemistry remain poorly understood. Although many methods exist for computing accurate electronic energies of molecules at equilibrium geometries, a consistent description of entire combustion reaction potential energy surfaces (PESs) requires multireference correlated wavefunction theories. Here we use bond dissociation energies (BDEs) as a foundational metric to benchmark methods based on multireference configuration interaction (MRCI) for several classes of oxygenated compounds (alcohols, aldehydes, carboxylic acids, and methyl esters). We compare results from multireference singles and doubles configuration interaction to those utilizing a posteriori and a priori size-extensivity corrections, benchmarked against experiment and coupled cluster theory. We demonstrate that size-extensivity corrections are necessary for chemically accurate BDE predictions even in relatively small molecules and furnish examples of unphysical BDE predictions resulting from using too-small orbital active spaces. We also outline the specific challenges in using MRCI methods for carbonyl-containing compounds. The resulting complete basis set extrapolated, size-extensivity-corrected MRCI scheme produces BDEs generally accurate to within 1 kcal/mol, laying the foundation for this scheme's use on larger molecules and for more complex regions of combustion PESs.

  16. A polarizable dipole-dipole interaction model for evaluation of the interaction energies for N-HO=C and C-HO=C hydrogen-bonded complexes.

    PubMed

    Li, Shu-Shi; Huang, Cui-Ying; Hao, Jiao-Jiao; Wang, Chang-Sheng

    2014-03-01

    In this article, a polarizable dipole-dipole interaction model is established to estimate the equilibrium hydrogen bond distances and the interaction energies for hydrogen-bonded complexes containing peptide amides and nucleic acid bases. We regard the chemical bonds N-H, C=O, and C-H as bond dipoles. The magnitude of the bond dipole moment varies according to its environment. We apply this polarizable dipole-dipole interaction model to a series of hydrogen-bonded complexes containing the N-HO=C and C-HO=C hydrogen bonds, such as simple amide-amide dimers, base-base dimers, peptide-base dimers, and ?-sheet models. We find that a simple two-term function, only containing the permanent dipole-dipole interactions and the van der Waals interactions, can produce the equilibrium hydrogen bond distances compared favorably with those produced by the MP2/6-31G(d) method, whereas the high-quality counterpoise-corrected (CP-corrected) MP2/aug-cc-pVTZ interaction energies for the hydrogen-bonded complexes can be well-reproduced by a four-term function which involves the permanent dipole-dipole interactions, the van der Waals interactions, the polarization contributions, and a corrected term. Based on the calculation results obtained from this polarizable dipole-dipole interaction model, the natures of the hydrogen bonding interactions in these hydrogen-bonded complexes are further discussed. PMID:24497309

  17. Solar System planetary tests of \\dot c/c

    E-print Network

    Lorenzo Iorio

    2009-05-15

    Analytical and numerical calculations show that a putative temporal variation of the speed of light c, with the meaning of space-time structure constant c_ST, assumed to be linear over timescales of about one century, would induce a secular precession of the longitude of the pericenter \\varpi of a test particle orbiting a spherically symmetric body. By comparing such a predicted effect to the corrections \\Delta\\dot\\varpi to the usual Newtonian/Einsteinian perihelion precessions of the inner planets of the Solar System, recently estimated by E.V. Pitjeva by fitting about one century of modern astronomical observations with the standard dynamical force models of the EPM epehemerides, we obtained \\dot c/c =(0.5 +/- 2)\\times 10^-7 yr^-1. Moreover, the possibility that \\dot c/c\

  18. Dislocation dissociation in some f.c.c. metals

    NASA Technical Reports Server (NTRS)

    Esterling, D. M.

    1980-01-01

    The dissociation of a perfect screw dislocation into a stacking fault in an f.c.c. lattice is modeled by the modified lattice statics. The interatomic potentials are obtained from the work of Esterling and Swaroop and differ substantially from those empirical potentials usually employed in defect simulations. The calculated stacking fault widths for aluminum, copper, and silver are in good agreement with weak beam microscopy results.

  19. A promising tool to achieve chemical accuracy for density functional theory calculations on Y-NO homolysis bond dissociation energies.

    PubMed

    Li, Hong Zhi; Hu, Li Hong; Tao, Wei; Gao, Ting; Li, Hui; Lu, Ying Hua; Su, Zhong Min

    2012-01-01

    A DFT-SOFM-RBFNN method is proposed to improve the accuracy of DFT calculations on Y-NO (Y = C, N, O, S) homolysis bond dissociation energies (BDE) by combining density functional theory (DFT) and artificial intelligence/machine learning methods, which consist of self-organizing feature mapping neural networks (SOFMNN) and radial basis function neural networks (RBFNN). A descriptor refinement step including SOFMNN clustering analysis and correlation analysis is implemented. The SOFMNN clustering analysis is applied to classify descriptors, and the representative descriptors in the groups are selected as neural network inputs according to their closeness to the experimental values through correlation analysis. Redundant descriptors and intuitively biased choices of descriptors can be avoided by this newly introduced step. Using RBFNN calculation with the selected descriptors, chemical accuracy (?1 kcalmol(-1)) is achieved for all 92 calculated organic Y-NO homolysis BDE calculated by DFT-B3LYP, and the mean absolute deviations (MADs) of the B3LYP/6-31G(d) and B3LYP/STO-3G methods are reduced from 4.45 and 10.53 kcalmol(-1) to 0.15 and 0.18 kcalmol(-1), respectively. The improved results for the minimal basis set STO-3G reach the same accuracy as those of 6-31G(d), and thus B3LYP calculation with the minimal basis set is recommended to be used for minimizing the computational cost and to expand the applications to large molecular systems. Further extrapolation tests are performed with six molecules (two containing Si-NO bonds and two containing fluorine), and the accuracy of the tests was within 1 kcalmol(-1). This study shows that DFT-SOFM-RBFNN is an efficient and highly accurate method for Y-NO homolysis BDE. The method may be used as a tool to design new NO carrier molecules. PMID:22942689

  20. Study of dielectron production in C + C collisions at 1 A GeV

    NASA Astrophysics Data System (ADS)

    Agakishiev, G.; Agodi, C.; Alvarez-Pol, H.; Balanda, A.; Bassini, R.; Bellia, G.; Belver, D.; Belyaev, A.; Blanco, A.; Bhmer, M.; Bortolotti, A.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Daz, J.; Dohrmann, F.; Dybczak, A.; Eberl, T.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Frhlich, I.; Galatyuk, T.; Garzn, J. A.; Gernhuser, R.; Gil, A.; Gilardi, C.; Golubeva, M.; Gonzlez-Daz, D.; Grosse, E.; Guber, F.; Heilmann, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kmpfer, B.; Kajetanowicz, M.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Kozuch, A.; Krsa, A.; Krizek, F.; Krcken, R.; Khn, W.; Kugler, A.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, J. S.; Lapidus, K.; Lopes, L.; Maier, L.; Mangiarotti, A.; Marn, J.; Markert, J.; Metag, V.; Michalska, B.; Mishra, D.; Morinire, E.; Mousa, J.; Mnch, M.; Mntz, C.; Naumann, L.; Novotny, R.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Prez Cavalcanti, T.; Pietraszko, J.; Pleskac, R.; Pospsil, V.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Schroeder, C.; Schwab, E.; Simon, R. S.; Sobolev, Yu. G.; Spataro, S.; Spruck, B.; Strbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tarantola, A.; Teilab, K.; Tlusty, P.; Toia, A.; Traxler, M.; Trebacz, R.; Tsertos, H.; Veretenkin, I.; Wagner, V.; Weber, M.; Wen, H.; Wisniowski, M.; Wojcik, T.; Wstenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zhou, P.; Zumbruch, P.; Hades Collaboration

    2008-05-01

    The emission of e+e- pairs from C + C collisions at an incident energy of 1 GeV per nucleon has been investigated. The measured production probabilities, spanning from the ?0-Dalitz to the ? / ? invariant-mass region, display a strong excess above the cocktail of standard hadronic sources. The bombarding-energy dependence of this excess is found to scale like pion production, rather than like eta production. The data are in good agreement with results obtained in the former DLS experiment.

  1. Study of dielectron production in C+C collisions at 1 AGeV

    E-print Network

    HADES Collaboration; G. Agakishiev; C. Agodi; H. Alvarez Pol; A. Balanda; R. Bassini; G. Bellia; D. Belver; A. Belyaev; A. Blanco; M. Boehmer; A. Bortolotti; J. L. Boyard; P. Braun-Munzinger; P. Cabanelas; E. Castro; T. Christ; M. Destefanis; J. Diaz; F. Dohrmann; A. Dybczak; T. Eberl; L. Fabbietti; P. Finocchiaro; P. Fonte; J. Friese; I. Froehlich; T. Galatyuk; J. A. Garzon; R. Gernhaeuser; A. Gil; C. Gilardi; M. Golubeva; D. Gonzalez Diaz; E. Grosse; F. Guber; M. Heilmann; T. Hennino; R. Holzmann; A. Ierusalimov; I. Iori; A. Ivashkin; M. Jurkovic; B. Kaempfer; K. Kanaki; T. Karavicheva; D. Kirschner; I. Koenig; W. Koenig; B. W. Kolb; R. Kotte; A. Kozuch; A. Krasa; F. Krizek; R. Kruecken; W. Kuehn; A. Kugler; A. Kurepin; J. Lamas Valverde; S. Lang; J. S. Lange; K. Lapidus; L. Lopes; L. Maier; A. Mangiarotti; J. Marin; J. Markert; V. Metag; B. Michalska; D. Mishra; E. Moriniere; J. Mousa; M. Muench; C. Muentz; L. Naumann; R. Novotny; J. Otwinowski; Y. C. Pachmayer; M. Palka; Y. Parpottas; V. Pechenov; O. Pechenova; T. Perez; J. Pietraszko; R. Pleskac; W. Przygoda; B. Ramstein; A. Reshetin; M. Roy Stephan; A. Rustamov; A. Sadovsky; B. Sailer; P. Salabura; A. Schmah; R. Simon; Y. Sobolev; S. Spataro; B. Spruck; H. Stroebele; J. Stroth; C. Sturm; M. Sudol; A. Tarantola; K. Teilab; P. Tlusty; A. Toia; M. Traxler; R. Trebacz; H. Tsertos; I. Veretenkin; V. Wagner; M. Weber; H. Wen; M. Wisniowski; T. Wojcik; J. Wuestenfeld; S. Yurevich; Y. Zanevsky; P. Zhou; P. Zumbruch

    2008-03-21

    The emission of e+e- pairs from C+C collisions at an incident energy of 1 GeV per nucleon has been investigated. The measured production probabilities, spanning from the pi0-Dalitz to the rho/omega! invariant-mass region, display a strong excess above the cocktail of standard hadronic sources. The bombarding-energy dependence of this excess is found to scale like pion production, rather than like eta production. The data are in good agreement with results obtained in the former DLS experiment.

  2. [Study on spectral emissivity of C/C composites].

    PubMed

    Zhu, Bo; Cao, Wei-Wei; Jing, Min; Dong, Xing-Guang; Wang, Cheng-Guo

    2009-11-01

    Different types of C/C composites were prepared by conventional molding, and the changes in normal spectral emissivity of samples were tested. The testing results show that spectral emissivity of C/C composite reinforced by short cut carbon fibers is generally higher than the sample reinforced by carbon cloth in the entire 2500-13000nm wavelength region. The structure of short cut carbon fibers is relatively loose and the number of material particles is less than other samples in unit volume, which increases the penetration depth of electromagnetic waves. This is the reason for higher normal spectral emissivity and better heat radiation property. Meanwhile, the test results of normal spectral emissivity for fiber perform and C/C composite samples show that the spectral emissivity of resin carbon is better than fiber carbon because of the difference in microstructure for the two kinds of carbon materials. Laser Raman spectroscopy was employed to analyze the microstructures of different carbon materials, and the results show that because sp3 and sp2 hybrid states of carbon atoms in resin carbon produced more vibration modes, the resin carbon also has higher normal spectral emissivity and better characteristics of heat radiation. PMID:20101951

  3. Quantum energy flow and the kinetics of water shuttling between hydrogen bonding sites on trans-formanilide

    NASA Astrophysics Data System (ADS)

    Agbo, Johnson K.; Leitner, David M.; Myshakin, Evgeniy M.; Jordan, Kenneth D.

    2007-08-01

    A potential energy surface for trans-formanilide (TFA)-H2O is calculated and applied to study energy flow in the complex as well as the kinetics of water shuttling between hydrogen bonding sites on TFA. In addition to the previously identified H2O-TFA(C=O) and H2O-TFA(NH) minima, with the water monomer bound to the C=O and NH groups, respectively, the new surface reveals a second local minimum with the water bound to the C=O group, and which lies energetically 310 cm-1 above the previously identified H2O-TFA(C=O) global minimum. On this surface, the energy barrier for water shuttling from H2O-TFA(C=O) global minimum to H2O-TFA(N-H) is 984 cm-1, consistent with the experimental bounds of 796 and 988 cm-1 [J. R. Clarkson et al. Science 307, 1443 (2005)]. The ergodicity threshold of TFA is calculated to be 1450 cm-1 for the TFA-H2O complex, the coupling to the water molecule is found to lower the ergodicity threshold to below the isomerization barrier. Energy transfer between the activated complex and the vibrational modes of TFA is calculated to be sufficiently rapid that the Rice-Ramsperger-Kassel-Marcus (RRKM) theory does not overestimate the rate of water shuttling. The possibility that the rate constant for water shuttling is higher than the RRKM theory estimate is discussed in light of the relatively high energy of the ergodicity threshold calculated for TFA.

  4. Pi Bond Orders and Bond Lengths

    ERIC Educational Resources Information Center

    Herndon, William C.; Parkanyi, Cyril

    1976-01-01

    Discusses three methods of correlating bond orders and bond lengths in unsaturated hydrocarbons: the Pauling theory, the Huckel molecular orbital technique, and self-consistent-field techniques. (MLH)

  5. Surface-catalyzed C-C covalent coupling strategies toward the synthesis of low-dimensional carbon-based nanostructures.

    PubMed

    Fan, Qitang; Gottfried, J Michael; Zhu, Junfa

    2015-08-18

    Carbon-based nanostructures have attracted tremendous interest because of their versatile and tunable properties, which depend on the bonding type of the constituting carbon atoms. Graphene, as the most prominent representative of the ?-conjugated carbon-based materials, consists entirely of sp(2)-hybridized carbon atoms and exhibits a zero band gap. Recently, countless efforts were made to open and tune the band gap of graphene for its applications in semiconductor devices. One promising method is periodic perforation, resulting in a graphene nanomesh (GNM), which opens the band gap while maintaining the exceptional transport properties. However, the typically employed lithographic approach for graphene perforation is difficult to control at the atomic level. The complementary bottom-up method using surface-assisted carbon-carbon (C-C) covalent coupling between organic molecules has opened up new possibilities for atomically precise fabrication of conjugated nanostructures like GNM and graphene nanoribbons (GNR), although with limited maturity. A general drawback of the bottom-up approach is that the desired structure usually does not represent the global thermodynamic minimum. It is therefore impossible to improve the long-range order by postannealing, because once the C-C bond formation becomes reversible, graphene as the thermodynamically most stable structure will be formed. This means that only carefully chosen precursors and reaction conditions can lead to the desired (non-graphene) material. One of the most popular and frequently used organic reactions for on-surface C-C coupling is the Ullmann reaction of aromatic halides. While experimentally simple to perform, the irreversibility of the C-C bond formation makes it a challenge to obtain long-range ordered nanostructures. With no postreaction structural improvement possible, the assembly process must be optimized to result in defect-free nanostructures during the initial reaction, requiring complete reaction of the precursors in the right positions. Incomplete connections typically result when mobile precursor monomers are blocked from reaching unsaturated reaction sites of the preformed nanostructures. For example, monomers may not be able to reach a randomly formed internal cavity of a two-dimensional (2D) nanostructure island due to steric hindrance in 2D confinement, leaving reaction sites in the internal cavity unsaturated. Wrong connections between precursor monomers, here defined as intermolecular C-C bonds forcing the monomer into a nonideal position within the structure, are usually irreversible and can induce further structural defects. The relative conformational flexibility of the monomer backbones permits connections between deformed monomers when they encounter strong steric hindrance. This, however, usually leads to heterogeneous structural motifs in the formed nanostructures. This Account reviews some of the latest developments regarding on-surface C-C coupling strategies toward the synthesis of carbon-based nanostructures by addressing the above-mentioned issues. The strategies include Ullmann coupling and other, "cleaner" alternative C-C coupling reactions like Glaser coupling, cyclo-dehydrogenation, and dehydrogenative coupling. The choice of substrate materials and precursor designs is crucial for optimizing substrate reactivity and precursor diffusion rates, and to reduce events of wrong linkage. Hierarchical polymerization is employed to steer the coupling route, which effectively improves the completeness of the reaction. Effects of byproducts on nanostructure formation is comprehended with both experimental and theoretical studies. PMID:26194462

  6. Investing in Bonds

    E-print Network

    Johnson, Jason; Polk, Wade

    2002-08-12

    Bonds, which are issued by governments and corporations, can be an important part of one's investment portfolio. U.S. government bonds, municipal bonds, zero-coupon bonds and other types are described. Also learn strategies for coping with inflation...

  7. Functional interactions in bacteriorhodopsin: a theoretical analysis of retinal hydrogen bonding with water.

    PubMed Central

    Nina, M; Roux, B; Smith, J C

    1995-01-01

    The light-driven proton pump, bacteriorhodopsin (bR) contains a retinal molecule with a Schiff base moiety that can participate in hydrogen-bonding interactions in an internal, water-containing channel. Here we combine quantum chemistry and molecular mechanics techniques to determine the geometries and energetics of retinal Schiff base-water interactions. Ab initio molecular orbital calculations are used to determine potential surfaces for water-Schiff base hydrogen-bonding and to characterize the energetics of rotation of the C-C single bond distal and adjacent to the Schiff base NH group. The ab initio results are combined with semiempirical quantum chemistry calculations to produce a data set used for the parameterization of a molecular mechanics energy function for retinal. Using the molecular mechanics force field the hydrated retinal and associated bR protein environment are energy-minimized and the resulting geometries examined. Two distinct sites are found in which water molecules can have hydrogen-bonding interactions with the Schiff base: one near the NH group of the Schiff base in a polar region directed towards the extracellular side, and the other near a retinal CH group in a relatively nonpolar region, directed towards the cytoplasmic side. Images FIGURE 1 FIGURE 2 FIGURE 6 FIGURE 8 PMID:7711248

  8. Effect of oxygen inhibition in two-step self-etch systems on surface free energy and dentin bond strength with a chemically cured resin composite.

    PubMed

    Yamaji, Ayumi; Tsujimoto, Akimasa; Asaoka, Tetsui; Matsuyoshi, Saki; Tsuchiya, Kenji; Takamizawa, Toshiki; Miyazaki, Masashi

    2014-09-01

    We compared the surface free energies and dentin bond strengths of two-step self-etch systems with and without an oxygen-inhibited layer. The adhesives were applied to self-etching primer-treated dentin surfaces of bovine incisors, after which the teeth were light-irradiated and the oxygen-inhibited layer was left intact or removed with ethanol. We determined surface free energies (?S) and their components by measuring the contact angles of three test liquids placed on the cured adhesives. We also measured the dentin bond strengths of chemically cured resin composite to the adhesives, with and without the oxygen-inhibited layer. For all surfaces, the estimated surface tension component, ?S(LW), was relatively constant. The Lewis base (?S(-)) component decreased significantly when the oxygen-inhibited layer was removed, whereas the Lewis acid (?S(+)) component slightly increased. The dentin bond strengths of the two-step self-etch systems did not significantly differ in relation to the presence of the oxygen-inhibited layer. Although the surface free energy of the adhesive was affected by the presence of the oxygen-inhibited layer, no changes in dentin bond strength were detected. PMID:25231146

  9. Raman Spectroscopy of Water-Ethanol Solutions: The Estimation of Hydrogen Bonding Energy and the Appearance of Clathrate-like Structures in Solutions.

    PubMed

    Dolenko, Tatiana A; Burikov, Sergey A; Dolenko, Sergey A; Efitorov, Alexander O; Plastinin, Ivan V; Yuzhakov, Viktor I; Patsaeva, Svetlana V

    2015-11-01

    The structure of aqueous alcohol solutions at the molecular level for many decades has remained an intriguing topic in numerous theoretical and practical investigations. The aberrant thermodynamic properties of water-alcohol mixtures are believed to be caused by the differences in energy of hydrogen bonding between water-water, alcohol-alcohol, and alcohol-water molecules. We present the Raman scattering spectra of water, ethanol, and water-ethanol solutions with 20 and 70 vol % of ethanol thoroughly measured and analyzed at temperatures varying from -10 to +70 C. Application of the MCR-ALS method allowed for each spectrum to extract contributions of molecules with different strengths of hydrogen bonding. The energy (enthalpy) of formation/weakening of hydrogen bonds was calculated using the slope of Van't Hoff plot. The energy of hydrogen bonding in 20 vol % of ethanol was found the highest among all the samples. This finding further supports appearance of clathrate-like structures in water-ethanol solutions with concentrations around 20 vol % of ethanol. PMID:26465255

  10. Basics of Fidelity Bonding.

    ERIC Educational Resources Information Center

    Kahn, Steven P.

    Fidelity bonds are important for an agency to hold to protect itself against any financial loss that can result from dishonest acts by its employees. Three types of fidelity bonds are available to an agency: (1) public official bonds; (2) dishonesty bonds; and (3) faithful performance bonds. Public official bonds are required by state law to be

  11. A dense and strong bonding collagen film for carbon/carbon composites

    NASA Astrophysics Data System (ADS)

    Cao, Sheng; Li, Hejun; Li, Kezhi; Lu, Jinhua; Zhang, Leilei

    2015-08-01

    A strong bonding collagen film was successfully prepared on carbon/carbon (C/C) composites. The surface conditions of the modified C/C composites were detected by contact angle measurements, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectra. The roughness, optical morphology, bonding strength and biocompatibility of collagen films at different pH values were detected by confocal laser scanning microscope (CLSM), universal test machine and cytology tests in vitro. After a 4-h modification in 30% H2O2 solution at 100 C, the contact angle on the surface of C/C composites was decreased from 92.3 to 65.3. Large quantities of hydroxyl, carboxyl and carbonyl functional groups were formed on the surface of the modified C/C composites. Then a dense and continuous collagen film was prepared on the modified C/C substrate. Bonding strength between collagen film and C/C substrate was reached to 8 MPa level when the pH value of this collagen film was 2.5 after the preparing process. With 2-day dehydrathermal treatment (DHT) crosslinking at 105 C, the bonding strength was increased to 12 MPa level. At last, the results of in vitro cytological test showed that this collagen film made a great improvement on the biocompatibility on C/C composites.

  12. The Dissociation Energies of CH4 and C2H2 Revisited

    NASA Technical Reports Server (NTRS)

    Partridge, Harry; Bauschlicher, Charles W., Jr.; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    The bond dissociation energies of CH4 and C2H2 and their fragments are investigated using basis set extrapolations and high levels of correlation. The computed bond dissociation energies (D(sub e)) are accurate to within 0.2 kcal/mol. The agreement with the experimental (D(sub 0)) values is excellent if we assume that the zero-point energy of C2H is 9.18 kcal/mol. The effect of core (1s) correlation on the bond dissociation energies of C-H bonds is shown to vary from 0.2 to 0.7 kcal/mol and that for C-C bonds varies from 0.4 to 2.2 kcal/mol.

  13. Sensor/ROIC Integration using Oxide Bonding

    E-print Network

    Zhenyu Ye; for the Fermilab Pixel R&D Group

    2009-02-16

    We explore the Ziptronix Direct Bond Interconnect technology for the integration of sensors and readout integrated circuits (ROICs) for high energy physics. The technology utilizes an oxide bond to form a robust mechanical connection between layers which serves to assist with the formation of metallic interlayer connections. We report on testing results of sample sensors bonded to ROICs and thinned to 100 microns.

  14. 30 CFR 556.53 - Additional bonds.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 2 2013-07-01 2013-07-01 false Additional bonds. 556.53 Section 556.53 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE LEASING OF SULPHUR OR OIL AND GAS IN THE OUTER CONTINENTAL SHELF Bonding 556.53 Additional bonds. (a) This paragraph...

  15. 30 CFR 556.53 - Additional bonds.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 2 2012-07-01 2012-07-01 false Additional bonds. 556.53 Section 556.53 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE LEASING OF SULPHUR OR OIL AND GAS IN THE OUTER CONTINENTAL SHELF Bonding 556.53 Additional bonds. (a) This paragraph...

  16. 30 CFR 556.53 - Additional bonds.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 2 2014-07-01 2014-07-01 false Additional bonds. 556.53 Section 556.53 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE LEASING OF SULPHUR OR OIL AND GAS IN THE OUTER CONTINENTAL SHELF Bonding 556.53 Additional bonds. (a) This paragraph...

  17. A Model for the Chemical Bond

    ERIC Educational Resources Information Center

    Magnasco, Valerio

    2004-01-01

    Bond stereochemistry in polyatomic hydrides is explained in terms of the principle of bond energies maximization, which yields X-H straight bonds and suggests the formation of appropriate sp hybrids on the central atom. An introduction to the electron charge distribution in molecules is given, and atomic, overlap, gross and formal charges are

  18. High spectral resolution Al2O3/B4C, SiC/Si, SiC/B4C, and SiC/C multilayer structures for the photon energies of 6 keV to 19 keV

    NASA Astrophysics Data System (ADS)

    Platonov, Yuriy Y.; Martynov, Vladimir V.; Kazimirov, Alexander; Lai, Barry

    2004-11-01

    A double multilayer monochromator with each multilayer composed of four stripes with different d-spacing providing spectral resolution of 0.3% to 0.8% in the energy range of 6keV to 19keV has been developed. Test multilayer structures with d-spacing from 2.3nm to 10.6nm have been deposited by magnetron sputtering. X-ray characterization has been performed at OSMIC by using a recently upgraded diffractometer setup and Cu-K? radiation and at the APS. The following material combinations were studied before the final choice of materials for the high energy resolution monochromator has been made: Al2O3/B4C, SiC/Si, SiC/B4C and SiC/C. To minimize the effect of internal stress built in multilayer structure on X-ray characteristics flat and thick 1" diameter silicon substrates supplied by Wave Precision Inc. were used for all calibration coatings. Final coatings were deposited on two 145mm long, 60mm wide and 30mm thick silicon substrates. Resolution of SiC/Si structures with d1=2.3nm, N1=1000 and d2=3nm, N2=700 was measured at Cu-K? with X-ray beam divergence of 14 arcsec to be 0.216% and 0.34% respectively. For plane waves the resolution is expected to be 0.13% and 0.19%, respectively.

  19. On a model of calculating bond strength

    NASA Technical Reports Server (NTRS)

    Yue, A. S.; Yang, T. T.; Lin, T. S.

    1976-01-01

    Diffusion bonding is a fabricating process to join the fibers and a matrix together forming a composite. The efficiency of the bonding process depends on temperature, time, and pressure. Based on a simplified pair potential model, an expression for the bond-energy at the fiber-matrix interface is formulated in terms of the above-mentioned three parameters. From this expression and the mean atomic distance, the bond-strength between the fibers and the matrix can be calculated.

  20. A quinone-assisted photoformation of energy-rich chemical bonds

    NASA Technical Reports Server (NTRS)

    Fox, S. W.; Adachi, T.; Stillwell, W.

    1980-01-01

    In a study of biochemical means of solar energy conversion, ADP and inorganic phosphates were converted to ATP by white light in the nonaqueous solvent dimethylformamide in the presence of tetrachloro-p-quinone or ubiquinone. Conversion of ADP to ATP has been accomplished in aqueous suspension by the use of cell-like structures aggregated from poly(aspartic acid, glutamic acid, tyrosine). This is believed to occur through the formation of dopaquinone in the peptide structure during illumination. The way in which the quantitative yield of ATP has been influenced by pH and by added substances, such as FeCl2, was studied.

  1. Compositions and chemical bonding in ceramics by quantitative electron energy-loss spectrometry

    SciTech Connect

    Bentley, J.; Horton, L.L.; McHargue, C.J.; McKernan, S.; Carter, C.B.; Revcolevschi, A.; Tanaka, S.; Davis, R.F.

    1993-12-31

    Quantitative electron energy-loss spectrometry was applied to a range of ceramic materials at a spatial resolution of <5 nm. Analysis of Fe L{sub 23} white lines indicated a low-spin state with a charge transfer of {approximately}1.5 electrons/atom onto the Fe atoms implanted into (amorphized) silicon carbide. Gradients of 2 to 5% in the Co:O stoichiometry were measured across 100-nm-thick Co{sub 3}O{sub 4} layers in an oxidized directionally solidified CoO-ZrO{sub 2} eutectic, with the highest O levels near the ZrO{sub 2}. The energy-loss near-edge structures were dramatically different for the two cobalt oxides; those for CO{sub 3}O{sub 4} have been incorrectly ascribed to CoO in the published literature. Kinetically stabilized solid solubility occurred in an AlN-SiC film grown by low-temperature molecular beam epitaxy (MBE) on {alpha}(6H)-SiC, and no detectable interdiffusion occurred in couples of MBE-grown AlN on SiC following annealing at up to 1750C. In diffusion couples of polycrystalline AlN on SiC, interfacial 8H sialon (aluminum oxy-nitride) and pockets of Si{sub 3}N{sub 4}-rich {beta}{prime} sialon in the SiC were detected.

  2. Ab initio study of symmetrical tilt grain boundaries in bcc Fe: structural units, magnetic moments, interfacial bonding, local energy and local stress.

    PubMed

    Bhattacharya, Somesh Kr; Tanaka, Shingo; Shiihara, Yoshinori; Kohyama, Masanori

    2013-04-01

    We present first-principle calculations on symmetric tilt grain boundaries (GBs) in bcc Fe. Using density functional theory (DFT), we studied the structural, electronic and magnetic properties of ?3(111) and ?11(332) GBs formed by rotation around the [110] axis. The optimized structures, GB energies and GB excess free volumes are consistent with previous DFT and classical simulation studies. The GB configurations can be interpreted by the structural unit model as given by Nakashima and Takeuchi (2000 ISIJ 86 357). Both the GBs are composed of similar structural units of three- and five-membered rings with different densities at the interface according to the rotation angle. The interface atoms with larger atomic volumes reveal higher magnetic moments than the bulk value, while the interface atoms with shorter bond lengths have reduced magnetic moments in each GB. The charge density and local density of states reveal that the interface bonds with short bond lengths have more covalent nature, where minority-spin electrons play a dominant role as the typical nature of ferromagnetic Fe. In order to understand the structural stability of these GBs, we calculated the local energy and local stress for each atomic region using the scheme of Shiihara et al (2010 Phys. Rev. B 81 075441). In each GB, the interface atoms with larger atomic volumes and enhanced magnetic moments reveal larger local energy increase and tensile stress. The interface atoms constituting more covalent-like bonds with reduced magnetic moments have lower local energy increase, contributing to the stabilization, while compressive stress is generated at these atoms. The relative stability between the two GBs can be understood by the local energies at the structural units. The local energy and local stress analysis is a powerful tool to investigate the structural properties of GBs based on the behavior of valence electrons. PMID:23478447

  3. Ab initio study of symmetrical tilt grain boundaries in bcc Fe: structural units, magnetic moments, interfacial bonding, local energy and local stress

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Somesh Kr; Tanaka, Shingo; Shiihara, Yoshinori; Kohyama, Masanori

    2013-04-01

    We present first-principle calculations on symmetric tilt grain boundaries (GBs) in bcc Fe. Using density functional theory (DFT), we studied the structural, electronic and magnetic properties of ?3(111) and ?11(332) GBs formed by rotation around the [110] axis. The optimized structures, GB energies and GB excess free volumes are consistent with previous DFT and classical simulation studies. The GB configurations can be interpreted by the structural unit model as given by Nakashima and Takeuchi (2000 ISIJ 86 357). Both the GBs are composed of similar structural units of three- and five-membered rings with different densities at the interface according to the rotation angle. The interface atoms with larger atomic volumes reveal higher magnetic moments than the bulk value, while the interface atoms with shorter bond lengths have reduced magnetic moments in each GB. The charge density and local density of states reveal that the interface bonds with short bond lengths have more covalent nature, where minority-spin electrons play a dominant role as the typical nature of ferromagnetic Fe. In order to understand the structural stability of these GBs, we calculated the local energy and local stress for each atomic region using the scheme of Shiihara et al (2010 Phys. Rev. B 81 075441). In each GB, the interface atoms with larger atomic volumes and enhanced magnetic moments reveal larger local energy increase and tensile stress. The interface atoms constituting more covalent-like bonds with reduced magnetic moments have lower local energy increase, contributing to the stabilization, while compressive stress is generated at these atoms. The relative stability between the two GBs can be understood by the local energies at the structural units. The local energy and local stress analysis is a powerful tool to investigate the structural properties of GBs based on the behavior of valence electrons.

  4. Hexacoordinate bonding and aromaticity in silicon phthalocyanine.

    PubMed

    Yang, Yang

    2010-12-23

    Si-E bondings in hexacoordinate silicon phthalocyanine were analyzed using bond order (BO), energy partition, atoms in molecules (AIM), electron localization function (ELF), and localized orbital locator (LOL). Bond models were proposed to explain differences between hexacoordinate and tetracoordinate Si-E bondings. Aromaticity of silicon phthalocyanine was investigated using nucleus-independent chemical shift (NICS), harmonic oscillator model of aromaticity (HOMA), conceptual density functional theory (DFT), ring critical point (RCP) descriptors, and delocalization index (DI). Structure, energy, bonding, and aromaticity of tetracoordinate silicon phthalocyanine were studied and compared with hexacoordinate one. PMID:21105726

  5. Mechanistic Investigation of Catalytic Carbon-Carbon Bond Activation and Formation by Platinum and Palladium Phosphine

    E-print Network

    Jones, William D.

    Mechanistic Investigation of Catalytic Carbon-Carbon Bond Activation and Formation by Platinum impede their development. First, the metal- carbon bond resulting from C-C insertion has been calculated Of this latter variety, Milstein and co-workers have discovered a system that is capable of removing a methyl

  6. Modeling the metal-semiconductor interaction: Analytical bond-order potential for platinum-carbon

    E-print Network

    Nordlund, Kai

    Modeling the metal-semiconductor interaction: Analytical bond-order potential for platinum for this potential makes use of the fact that chemical bonding in both covalent systems and d-transition metals can for describing the C-C/Pt-Pt/Pt-C interactions. It resembles, in the case of the pure metal interaction

  7. Free Energy Diagram for the Heterogeneous Enzymatic Hydrolysis of Glycosidic Bonds in Cellulose.

    PubMed

    Srensen, Trine Holst; Cruys-Bagger, Nicolaj; Borch, Kim; Westh, Peter

    2015-09-01

    Kinetic and thermodynamic data have been analyzed according to transition state theory and a simplified reaction scheme for the enzymatic hydrolysis of insoluble cellulose. For the cellobiohydrolase Cel7A from Hypocrea jecorina (Trichoderma reesei), we were able to measure or collect relevant values for all stable and activated complexes defined by the reaction scheme and hence propose a free energy diagram for the full heterogeneous process. For other Cel7A enzymes, including variants with and without carbohydrate binding module (CBM), we obtained activation parameters for the association and dissociation of the enzyme-substrate complex. The results showed that the kinetics of enzyme-substrate association (i.e. formation of the Michaelis complex) was almost entirely entropy-controlled and that the activation entropy corresponded approximately to the loss of translational and rotational degrees of freedom of the dissolved enzyme. This implied that the transition state occurred early in the path where the enzyme has lost these degrees of freedom but not yet established extensive contact interactions in the binding tunnel. For dissociation, a similar analysis suggested that the transition state was late in the path where most enzyme-substrate contacts were broken. Activation enthalpies revealed that the rate of dissociation was far more temperature-sensitive than the rates of both association and the inner catalytic cycle. Comparisons of one- and two-domain variants showed that the CBM had no influence on the transition state for association but increased the free energy barrier for dissociation. Hence, the CBM appeared to promote the stability of the complex by delaying dissociation rather than accelerating association. PMID:26183776

  8. Determination of consecutive bond energies by photoionization of SbH[sub [ital n

    SciTech Connect

    Ruscic, B.; Berkowitz, J. )

    1993-10-15

    A photoionization mass spectrometric study of SbH[sub 3] is presented. The adiabatic ionization potential (IP) of SbH[sub 3] is [le]9.40[plus minus]0.02 eV. The lowest energy fragment ion, SbH[sup +] (+H[sub 2]), has an appearance potential (0 K) of 9.73[sub 0][plus minus]0.00[sub 8] eV, while SbH[sub 2][sup +] has an AP of 11.66[plus minus]0.02 eV. The transient species SbH[sub 2] and SbH are generated [ital in] [ital situ] by reacting F atoms with SbH[sub 3]. The IP of SbH[sub 2], forming SbH[sub 2][sup +] ([ital X] [sup 1][ital A][sub 1]), is 8.731[plus minus]0.012 eV. The IP of SbH ([ital X] [sup 3][Sigma][sup [minus

  9. "Vibrational bonding": a new type of chemical bond is discovered.

    PubMed

    Rhodes, Christopher J; Macrae, Roderick M

    2015-01-01

    A long-sought but elusive new type of chemical bond, occurring on a minimum-free, purely repulsive potential energy surface, has recently been convincingly shown to be possible on the basis of high-level quantum-chemical calculations. This type of bond, termed a vibrational bond, forms because the total energy, including the dynamical energy of the nuclei, is lower than the total energy of the dissociated products, including their vibrational zero-point energy. For this to be the case, the ZPE of the product molecule must be very high, which is ensured by replacing a conventional hydrogen atom with its light isotope muonium (Mu, mass = 1/9 u) in the system Br-H-Br, a natural transition state in the reaction between Br and HBr. A paramagnetic species observed in the reaction Mu +Br2 has been proposed as a first experimental sighting of this species, but definitive identification remains challenging. PMID:25942773

  10. Chemical Distribution and Bonding of Lithium in Intercalated Graphite: Identification with Optimized Electron Energy Loss Spectroscopy

    SciTech Connect

    Zhu, Y.; Wang, F.; Graetz, J.; Moreno, M.S.; Ma, C.; Wu, L.; Volkov, V.

    2011-02-01

    Direct mapping of the lithium spatial distribution and the chemical state provides critical information on structure-correlated lithium transport in electrode materials for lithium batteries. Nevertheless, probing lithium, the lightest solid element in the periodic table, poses an extreme challenge with traditional X-ray or electron scattering techniques due to its weak scattering power and vulnerability to radiation damage. Here, we report nanoscale maps of the lithium spatial distribution in electrochemically lithiated graphite using electron energy loss spectroscopy in the transmission electron microscope under optimized experimental conditions. The electronic structure of the discharged graphite was obtained from the near-edge fine structure of the Li and C K-edges and ab initio calculations. A 2.7 eV chemical shift of the Li K-edge, along with changes in the density of states, reveals the ionic nature of the intercalated lithium with significant charge transfer to the graphene sheets. Direct mapping of lithium in graphite revealed nanoscale inhomogeneities (nonstoichiometric regions), which are correlated with local phase separation and structural disorder (i.e., lattice distortion and dislocations) as observed by high-resolution transmission electron microscopy. The surface solid-electrolyte interphase (SEI) layer was also imaged and determined to have a thickness of 10-50 nm, covering both edge and basal planes with LiF as its primary inorganic component. The Li K-edge spectroscopy and mapping, combined with electron microscopy-based structural analysis provide a comprehensive view of the structure-correlated lithium intercalation in graphite and of the formation of the SEI layer.

  11. Theoretical insights into the structures and mechanical properties of HMX/NQ cocrystal explosives and their complexes, and the influence of molecular ratios on their bonding energies.

    PubMed

    Li, Yong-Xiang; Chen, Shu-Sen; Ren, Fu-de

    2015-09-01

    Molecular dynamics (MD) methods were employed to study the binding energies and mechanical properties of selected crystal planes of 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX)/nitroguanidine (NQ) cocrystals at different molecular molar ratios. The densities and detonation velocities of the cocrystals at different molar ratios were estimated. The intermolecular interaction and bond dissociation energy (BDE) of the N-NO2 bond in the HMX:NQ (1:1) complex were calculated using the B3LYP, MP2(full) and M06-2X methods with the 6-311++G(d,p) and 6-311++G(2df,2p) basis sets. The results indicated that the HMX/NQ cocrystal prefers cocrystalizing in a 1:1 molar ratio, and the cocrystallization is dominated by the (0 2 0) and (1 0 0) facets. The K, G, and E values of the ratio of 1:1 are smaller than those of the other ratios, and the 1:1 cocrystal has the best ductility. The N-NO2 bond becomes stronger upon the formation of the intermolecular H-bonding interaction and the sensitivity of HMX decreases in the cocrystal. This sensitivity change in the HMX/NQ cocrystal originates not only from the formation of the intermolecular interaction but also from the increment of the BDE of N-NO2 bond in comparison with isolated HMX. The HMX/NQ (1:1) cocrystal exhibits good detonation performance. Reduced density gradient (RDG) reveals the nature of cocrystallization. Analysis of the surface electrostatic potential further confirmed that the sensitivity decreases in complex (or cocrystal) in comparison with that in isolated HMX. PMID:26318201

  12. Physical Nature of Hydrogen Bond

    E-print Network

    Zhyganiuk, I V

    2015-01-01

    The physical nature and the correct definition of hydrogen bond (H-bond) are considered.\\,\\,The influence of H-bonds on the thermodynamic, kinetic, and spectroscopic properties of water is analyzed.\\,\\,The conventional model of H-bonds as sharply directed and saturated bridges between water molecules is incompatible with the behavior of the specific volume, evaporation heat, and self-diffusion and kinematic shear viscosity coefficients of water. On the other hand, it is shown that the variation of the dipole moment of a water molecule and the frequency shift of valence vibrations of a hydroxyl group can be totally explained in the framework of the electrostatic model of H-bond.\\,\\,At the same time, the temperature dependences of the heat capacity of water in the liquid and vapor states clearly testify to the existence of weak H-bonds.\\,\\,The analysis of a water dimer shows that the contribution of weak H-bonds to its ground state energy is approximately 4--5 times lower in comparison with the energy of electr...

  13. Etching of porous and solid SiO2 in Ar/c-C4F8, O2/c-C4F8 and Ar/O2/c-C4F8 plasmas

    E-print Network

    Kushner, Mark

    , Illinois 61801 Mark J. Kushnerb) Department of Electrical and Computer Engineering, University of Illinois mechanism was validated by comparison to experiments for blanket etching of solid and porous SiO2 in Ar/c-C4F8 and O2/c-C4F8 plasmas using inductively coupled plasma reactors. We found that the blanket etch

  14. Synthesis of Polyheteroaromatic Compounds via Rhodium-Catalyzed Multiple C-H Bond Activation and Oxidative Annulation.

    PubMed

    Peng, Shiyong; Liu, Suna; Zhang, Sai; Cao, Shengyu; Sun, Jiangtao

    2015-10-16

    Polyheteroaromatic compounds are potential optoelectronic conjugated materials due to their electro- and photochemical properties. Transition-metal-catalyzed multiple C-H activation and sequential oxidative annulation allows rapidly assembling of those compounds from readily available starting materials. A rhodium-catalyzed cascade oxidative annulation of ?-enamino esters or 4-aminocoumarins with internal alkynes is described to access those compounds, featuring multiple C-H/N-H bond cleavages and sequential C-C/C-N bond formations in one pot. PMID:26439472

  15. Determination and interrelation of bond heterolysis and homolysis energies in solution. Final report, January 1988-August 1991

    SciTech Connect

    Arnett, E.M.

    1993-01-01

    Solution phase heats of heterolysis Delta H(sub(het)) and homolysis Delta H(sub(homo)) were determined for covalent bonds that can be cleaved to produce resonance-stabilized carbenium ions, anions, and radicals. Simple and broadly applicable correlation equations were developed which relate Delta H(sub(het)) to ion stabilization properties pK(sub(R+5)) and pK(sub a) and relate Delta H(sub(homo)) to radical stabilization properties (AOPs and CRPs). Important conclusions from the study are: (1) there is no general correlation between Delta H(sub(het)) and Delta H(sub(homo)) which implies that heterolytic bond cleavage pathways in coal will be quite different than the homolytic bond cleavage pathways associated with coal thermolysis; (2) many covalent bonds in coal which require high temperature for homolytic cleavage may be susceptible to heterolytic cleavage under mild conditions; and (3) coal conversion process chemistry based upon heterolytic bond cleavage may be more selective and controllable than homolytic bond cleavage associated with coal thermolysis.

  16. Dispersion-correcting potentials can significantly improve the bond dissociation enthalpies and noncovalent binding energies predicted by density-functional theory

    SciTech Connect

    DiLabio, Gino A.; Koleini, Mohammad; Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4

    2014-05-14

    Dispersion-correcting potentials (DCPs) are atom-centered Gaussian functions that are applied in a manner that is similar to effective core potentials. Previous work on DCPs has focussed on their use as a simple means of improving the ability of conventional density-functional theory methods to predict the binding energies of noncovalently bonded molecular dimers. We show in this work that DCPs developed for use with the LC-?PBE functional along with 6-31+G(2d,2p) basis sets are capable of simultaneously improving predicted noncovalent binding energies of van der Waals dimer complexes and covalent bond dissociation enthalpies in molecules. Specifically, the DCPs developed herein for the C, H, N, and O atoms provide binding energies for a set of 66 noncovalently bonded molecular dimers (the S66 set) with a mean absolute error (MAE) of 0.21 kcal/mol, which represents an improvement of more than a factor of 10 over unadorned LC-?PBE/6-31+G(2d,2p) and almost a factor of two improvement over LC-?PBE/6-31+G(2d,2p) used in conjunction with the D3 pairwise dispersion energy corrections. In addition, the DCPs reduce the MAE of calculated X-H and X-Y (X,Y = C, H, N, O) bond dissociation enthalpies for a set of 40 species from 3.2 kcal/mol obtained with unadorned LC-?PBE/6-31+G(2d,2p) to 1.6 kcal/mol. Our findings demonstrate that broad improvements to the performance of DFT methods may be achievable through the use of DCPs.

  17. Dispersion-correcting potentials can significantly improve the bond dissociation enthalpies and noncovalent binding energies predicted by density-functional theory

    NASA Astrophysics Data System (ADS)

    DiLabio, Gino A.; Koleini, Mohammad

    2014-05-01

    Dispersion-correcting potentials (DCPs) are atom-centered Gaussian functions that are applied in a manner that is similar to effective core potentials. Previous work on DCPs has focussed on their use as a simple means of improving the ability of conventional density-functional theory methods to predict the binding energies of noncovalently bonded molecular dimers. We show in this work that DCPs developed for use with the LC-?PBE functional along with 6-31+G(2d,2p) basis sets are capable of simultaneously improving predicted noncovalent binding energies of van der Waals dimer complexes and covalent bond dissociation enthalpies in molecules. Specifically, the DCPs developed herein for the C, H, N, and O atoms provide binding energies for a set of 66 noncovalently bonded molecular dimers (the "S66" set) with a mean absolute error (MAE) of 0.21 kcal/mol, which represents an improvement of more than a factor of 10 over unadorned LC-?PBE/6-31+G(2d,2p) and almost a factor of two improvement over LC-?PBE/6-31+G(2d,2p) used in conjunction with the "D3" pairwise dispersion energy corrections. In addition, the DCPs reduce the MAE of calculated X-H and X-Y (X,Y = C, H, N, O) bond dissociation enthalpies for a set of 40 species from 3.2 kcal/mol obtained with unadorned LC-?PBE/6-31+G(2d,2p) to 1.6 kcal/mol. Our findings demonstrate that broad improvements to the performance of DFT methods may be achievable through the use of DCPs.

  18. , 2006, . 47, 5, c. 557--567 http://www.izdatgeo.ru PP C C CX X

    E-print Network

    Cerveny, Vlastislav

    , 2006, . 47, 5, c. 557--567 http://www.izdatgeo.ru 550.834 PP C C CX X P P CP . p Republic pp c px px cx x, pcpcpxc p p p cp, c c c. c cc p P- S-, pcpcpxc px x - p. pp c p SH-, pcpcpxc c- c cp p p cp. xppc p- p c p c c p cpc. p, cc c cc p pcpcp p c pc pccp c . p c c p

  19. Acid Gradient across Plasma Membrane Can Drive Phosphate Bond Synthesis in Cancer Cells: Acidic Tumor Milieu as a Potential Energy Source

    PubMed Central

    Dhar, Gautam; Sen, Suvajit; Chaudhuri, Gautam

    2015-01-01

    Aggressive cancers exhibit an efficient conversion of high amounts of glucose to lactate accompanied by acid secretion, a phenomenon popularly known as the Warburg effect. The acidic microenvironment and the alkaline cytosol create a proton-gradient (acid gradient) across the plasma membrane that represents proton-motive energy. Increasing experimental data from physiological relevant models suggest that acid gradient stimulates tumor proliferation, and can also support its energy needs. However, direct biochemical evidence linking extracellular acid gradient to generation of intracellular ATP are missing. In this work, we demonstrate that cancer cells can synthesize significant amounts of phosphate-bonds from phosphate in response to acid gradient across plasma membrane. The noted phenomenon exists in absence of glycolysis and mitochondrial ATP synthesis, and is unique to cancer. Biochemical assays using viable cancer cells, and purified plasma membrane vesicles utilizing radioactive phosphate, confirmed phosphate-bond synthesis from free phosphate (Pi), and also localization of this activity to the plasma membrane. In addition to ATP, predominant formation of pyrophosphate (PPi) from Pi was also observed when plasma membrane vesicles from cancer cells were subjected to trans-membrane acid gradient. Cancer cytosols were found capable of converting PPi to ATP, and also stimulate ATP synthesis from Pi from the vesicles. Acid gradient created through glucose metabolism by cancer cells, as observed in tumors, also proved critical for phosphate-bond synthesis. In brief, these observations reveal a role of acidic tumor milieu as a potential energy source and may offer a novel therapeutic target. PMID:25874623

  20. Picosecond IR-UV pump-probe spectroscopic study of the dynamics of the vibrational relaxation of jet-cooled phenol. II. Intracluster vibrational energy redistribution of the OH stretching vibration of hydrogen-bonded clusters.

    PubMed

    Kayano, Masakazu; Ebata, Takayuki; Yamada, Yuji; Mikami, Naohiko

    2004-04-22

    A picosecond time-resolved IR-UV pump-probe spectroscopic study has been carried out for investigating the intracluster vibrational energy redistribution (IVR) and subsequent dissociation of hydrogen-bonded clusters of phenol (C6H5OH) and partially deuterated phenol (C6D5OH, phenol-d5) with various solvent molecules. The H-bonded OH stretching vibration was pumped by a picosecond IR pulse, and the transient S1-S0 UV spectra from the pumped level as well as the redistributed levels were observed with a picosecond UV laser. Two types of hydrogen-bonded clusters were investigated with respect to the effect of the H-bonding strength on the energy flow process: the first is of a strong "sigma-type H-bond" such as phenol-(dimethyl ether)(n=1) and phenol dimer, and the second is phenol-(ethylene)(n=1) having a weak "pi-type H-bond." It was found that the population of the IR-pumped OH level exhibits a single-exponential decay, whose rate increases with the H-bond strength. On the other hand, the transient UV spectrum due to the redistributed levels showed a different time evolutions at different monitoring UV frequency. From an analysis of the time profiles of the transient UV spectra, the following three-step scheme has been proposed for describing the energy flow starting from the IVR of the initially excited H-bonded OH stretching level to the dissociation of the H bond. (1) The intramolecular vibrational energy redistribution takes place within the phenolic site, preparing a hot phenol. (2) The energy flows from the hot phenol to the intermolecular vibrational modes of the cluster. (3) Finally, the hydrogen bond dissociates. Among the three steps, the rate constant of the first step was strongly dependent on the H-bond strength, while the rate constants of the other two steps were almost independent of the H-bond strength. For the dissociation of the hydrogen bond, the observed rate constants were compared with those calculated by the Rice, Ramsperger, Kassel, and Marcus model. The result suggests that dissociation of the hydrogen bond takes place much faster than complete energy randomization within the clusters. PMID:15267651

  1. Defect structures in deformed F.C.C. metals

    SciTech Connect

    Dai, Y.; Victoria, M.

    1997-08-01

    A high density of small defect clusters, similar to those observed in irradiated or quenched metals, has been observed in the deformed f.c.c. metals Cu, Au and Ni. The preliminary results show that the defect clusters are predominantly stacking fault tetrahedral (SFT). The SFT number density, rather than the size distribution, is deformation dependent. The defect cluster density is greater in the vicinities of dislocation tangles and grain boundaries. Their size distribution is wider than that produced by irradiation with an important number of larger clusters being formed. It is argued that these deformation-produced clusters may play a role in determining the flow stress and work hardening at low deformations.

  2. Diffusion Monte Carlo Study of Bond Dissociation Energies for BH2, B(OH)2, BCl2, and BCl

    NASA Astrophysics Data System (ADS)

    Li, Hui-ran; Cheng, Xin-lu; Zhang, Hong

    2012-02-01

    On basis of bond dissociation energies (BDEs) for BH2, B(OH)2, BCl2, and BCl, the diffusion Monte Carlo (DMC) method is applied to explore the BDEs of HB-H, HOB-OH, ClB-Cl, and B-Cl. The effect of the choice of orbitals, as well as the backflow transformation, is studied. The Slater-Jastrow DMC algorithm gives BDEs of 359.10.12 kJ/mol for HB-H, 410.50.50 kJ/mol for HOB-OH, 357.81.46 kJ/mol for ClB-Cl, and 504.50.96 kJ/mol for B-Cl using B3PW91 orbitals and similar BDEs when B3LYP orbitals are used. DMC with backflow corrections (BF-DMC) gives a HB-H BDE of 369.90.12 kJ/mol which is close to one of the available experimental value (375.8 kJ/mol). In the case of HOB-OH BDE, the BF-DMC calculation is 446.01.84 kJ/mol that is closer to the experimental BDE. The BF-DMC BDE for ClB-Cl is 343.22.34 kJ/mol and the BF-DMC B-Cl BDE is 523.30.33 kJ/mol, which are close to the experimental BDEs, 341.9 and 530.0 kJ/mol, respectively.

  3. A dynamical model of the chemical bond

    E-print Network

    Holger F. Hofmann

    1997-06-13

    A new approach to chemical bonding is introduced in order to provide an improved understanding of the connection between basic quantum mechanics and the covalent pair bond. It's focus is on the fact that the energy of the bond is largely given by the kinetic energy of the electrons, while the Coulomb forces are only comparable to the kinetic energy terms close to the atomic nuclei, where they define the shape and the size of the atomic orbitals. If atomic orbitals are used as a starting point, the kinetic energy operator is sufficient to determine the energy of the chemical bond. The simple mathematical structure of this operator allows a calculation of bond energy as a function of the distance between the atoms. For Gaussian wavefunctions, it is possible to calculate this bonding potential analytically, determining the bond length, the bond energy and the elasticity of the bond from only a single parameter, the width of the atomic wavefunction. It is shown that the results correspond surprisingly well with experimental values for diatomic molecules.

  4. 29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules ...

  5. 29 CFR 2580.412-20 - Use of existing bonds, separate bonds and additional bonding.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...bonds, separate bonds and additional bonding. 2580.412-20 Section 2580...DEPARTMENT OF LABOR TEMPORARY BONDING RULES UNDER THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES General Bond Rules ...

  6. The antimony-group 11 chemical bond: Dissociation energies of the diatomic molecules CuSb, AgSb, and AuSb

    SciTech Connect

    Carta, V.; Ciccioli, A. E-mail: andrea.ciccioli@uniroma1.it; Gigli, G. E-mail: andrea.ciccioli@uniroma1.it

    2014-02-14

    The intermetallic molecules CuSb, AgSb, and AuSb were identified in the effusive molecular beam produced at high temperature under equilibrium conditions in a double-cell-like Knudsen source. Several gaseous equilibria involving these species were studied by mass spectrometry as a function of temperature in the overall range 13491822 K, and the strength of the chemical bond formed between antimony and the group 11 metals was for the first time measured deriving the following thermochemical dissociation energies (D{sub 0}{sup ?}, kJ/mol): 186.7 5.1 (CuSb), 156.3 4.9 (AgSb), 241.3 5.8 (AuSb). The three species were also investigated computationally at the coupled cluster level with single, double, and noniterative quasiperturbative triple excitations (CCSD(T)). The spectroscopic parameters were calculated from the potential energy curves and the dissociation energies were evaluated at the Complete Basis Set limit, resulting in an overall good agreement with experimental values. An approximate evaluation of the spin-orbit effect was also performed. CCSD(T) calculations were further extended to the corresponding group 11 arsenide species which are here studied for the first time and the following dissociation energies (D{sub 0}{sup ?}, kJ/mol): 190 10 (CuAs), 151 10 (AgAs), 240 15 (AuAs) are proposed. Taking advantage of the new experimental and computational information here presented, the bond energy trends along group 11 and 4th and 5th periods of the periodic table were analyzed and the bond energies of the diatomic species CuBi and AuBi, yet experimentally unobserved, were predicted on an empirical basis.

  7. Europhysics Letters PREPRINT Bond-breaking mechanism of sputtering

    E-print Network

    Nordlund, Kai

    and molecules by colliding with and breaking chemical bonds between the atoms. In the particular case chemical (preferential bonding of surface atoms to the impinging ions), and thus should not have a strong simulation model, capable of both describing chemical bonding, high-energy recoiling atoms, and bond breaking

  8. On The Nature of the Halogen Bond.

    PubMed

    Wang, Changwei; Danovich, David; Mo, Yirong; Shaik, Sason

    2014-09-01

    The wide-ranging applications of the halogen bond (X-bond), notably in self-assembling materials and medicinal chemistry, have placed this weak intermolecular interaction in a center of great deal of attention. There is a need to elucidate the physical nature of the halogen bond for better understanding of its similarity and differences vis--vis other weak intermolecular interactions, for example, hydrogen bond, as well as for developing improved force-fields to simulate nano- and biomaterials involving X-bonds. This understanding is the focus of the present study that combines the insights of a bottom-up approach based on ab initio valence bond (VB) theory and the block-localized wave function (BLW) theory that uses monomers to reconstruct the wave function of a complex. To this end and with an aim of unification, we studied the nature of X-bonds in 55 complexes using the combination of VB and BLW theories. Our conclusion is clear-cut; most of the X-bonds are held by charge transfer interactions (i.e., intermolecular hyperconjugation) as envisioned more than 60 years ago by Mulliken. This is consistent with the experimental and computational findings that X-bonds are more directional than H-bonds. Furthermore, the good linear correlation between charge transfer energies and total interaction energies partially accounts for the success of simple force fields in the simulation of large systems involving X-bonds. PMID:26588518

  9. Ir-Catalyzed Functionalization of C-H Bonds

    NASA Astrophysics Data System (ADS)

    Choi, Jongwook; Goldman, Alan S.

    The ability to selectively functionalize C-H bonds holds enormous potential value in virtually every sphere of organic chemistry, from fuels to pharmaceuticals. Transition metal complexes have shown great promise in this context. Iridium provided the first examples of oxidative addition of C-H bonds; this addition is key to iridium's leading role in alkane dehydrogenation and related reactions. Catalysts based on iridium have also proven highly effective for valuable borylations of C-H bonds and, to a lesser extent, for C-Si coupling. Compared with other platinum group metals, iridium chemistry has not been developed as extensively for the elaboration of C-C bonds from C-H bonds, but significant promise is indicated, particularly for coupling with simple hydrocarbons which lack functionalities that can act as directing groups.

  10. SnSb-TiC-C nanocomposite alloy anodes for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Leibowitz, Joshua; Allcorn, Eric; Manthiram, Arumugam

    2015-04-01

    SnSb-TiC-C nanocomposite alloy anodes for lithium-ion batteries have been synthesized by a mechanochemical process involving high-energy mechanical milling of Ti-Sn and Ti-Sb precursors with carbon black. Characterization of the formed nanocomposites using x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) reveals that these alloys are composed of crystalline nanoparticles of SnSb dispersed in a matrix of crystalline TiC and amorphous carbon. The SnSb-TiC-C alloy shows an initial gravimetric capacity of 769 mAh g-1 (1385 mAh cm-3), an initial coulombic efficiency of 84.9%, and a tap density of 1.8 g cm-3. The buffer matrix of TiC and carbon in the nanocomposite alloy anodes accommodates the large volume change occurring during the charge-discharge process and leads to enhanced cyclability compared to pure SnSb anodes as well as previously published SnSb composites.

  11. Bonding PMMA microfluidics using commercial microwave ovens

    NASA Astrophysics Data System (ADS)

    Toossi, A.; Moghadas, H.; Daneshmand, M.; Sameoto, D.

    2015-08-01

    In this paper, a novel low-cost, rapid substrate-bonding technique is successfully applied to polymethyl methacrylate (PMMA) microfluidics bonding for the first time. This technique uses a thin intermediate metallic microwave susceptor layer at the interface of the bonding site (microchannels) which produces localized heating required for bonding during microwave irradiation. The metallic susceptor pattern is designed using a multiphysics simulation model developed in ANSYS Multiphysics software (high-frequency structural simulation (HFSS) coupled with ANSYS-Thermal). In our experiments, the required microwave energy for bonding is delivered using a relatively inexpensive, widely accessible commercial microwave oven. Using this technique, simple PMMA microfluidics prototypes are successfully bonded and sealed in less than 35?seconds with a minimum measured bond strength of 1.375?MPa.

  12. Long time fluctuation of liquid water: l/f spectrum of energy fluctuation in hydrogen bond network rearrangement dynamics

    E-print Network

    Ramaswamy, Ram

    convergency in Monte Carlo (MC) simulations. The present analysis shows the exist- ence of very long time Liquid water is a "frustrated" system with multiple random hydrogen bond network structures. Upon become partially broken (frustrated). The system starts to undergo rearrangement dynamics of the hydrogen

  13. Theoretical in-Solution Conformational/Tautomeric Analyses for Chain Systems with Conjugated Double Bonds Involving Nitrogen(s)

    PubMed Central

    Nagy, Peter I.

    2015-01-01

    Conformational/tautomeric transformations for X=CHCH=Y structures (X = CH2, O, NH and Y = NH) have been studied in the gas phase, in dichloromethane and in aqueous solutions. The paper is a continuation of a former study where s-cis/s-trans conformational equilibria were predicted for analogues. The s-trans conformation is preferred for the present molecules in the gas phase on the basis of its lowest internal free energy as calculated at the B97D/aug-cc-pvqz and CCSD(T)CBS (coupled-cluster singles and doubles with non-iterative triples extrapolated to the complete basis set) levels. Transition state barriers are of 2936 kJ/mol for rotations about the central CC bonds. In solution, an s-trans form is still favored on the basis of its considerably lower internal free energy compared with the s-cis forms as calculated by IEF-PCM (integral-equation formalism of the polarizable continuum dielectric solvent model) at the theoretical levels indicated. A tetrahydrate model in the supermolecule/continuum approach helped explore the 2solute-solvent hydrogen bond pattern. The calculated transition state barrier for rotation about the CC bond decreased to 27 kJ/mol for the tetrahydrate. Considering explicit solvent models, relative solvation free energies were calculated by means of the free energy perturbation method through Monte Carlo simulations. These calculated values differ remarkably from those by the PCM approach in aqueous solution, nonetheless the same prevalent conformation was predicted by the two methods. Aqueous solution structure-characteristics were determined by Monte Carlo. Equilibration of conformers/tautomers through water-assisted double proton-relay is discussed. This mechanism is not viable, however, in non-protic solvents where the calculated potential of mean force curve does not predict remarkable solute dimerization and subsequent favorable orientation. PMID:25984602

  14. Theoretical in-Solution Conformational/Tautomeric Analyses for Chain Systems with Conjugated Double Bonds Involving Nitrogen(s).

    PubMed

    Nagy, Peter I

    2015-01-01

    Conformational/tautomeric transformations for X=CH-CH=Y structures (X = CH2, O, NH and Y = NH) have been studied in the gas phase, in dichloromethane and in aqueous solutions. The paper is a continuation of a former study where s-cis/s-trans conformational equilibria were predicted for analogues. The s-trans conformation is preferred for the present molecules in the gas phase on the basis of its lowest internal free energy as calculated at the B97D/aug-cc-pvqz and CCSD(T)CBS (coupled-cluster singles and doubles with non-iterative triples extrapolated to the complete basis set) levels. Transition state barriers are of 29-36 kJ/mol for rotations about the central C-C bonds. In solution, an s-trans form is still favored on the basis of its considerably lower internal free energy compared with the s-cis forms as calculated by IEF-PCM (integral-equation formalism of the polarizable continuum dielectric solvent model) at the theoretical levels indicated. A tetrahydrate model in the supermolecule/continuum approach helped explore the 2solute-solvent hydrogen bond pattern. The calculated transition state barrier for rotation about the C-C bond decreased to 27 kJ/mol for the tetrahydrate. Considering explicit solvent models, relative solvation free energies were calculated by means of the free energy perturbation method through Monte Carlo simulations. These calculated values differ remarkably from those by the PCM approach in aqueous solution, nonetheless the same prevalent conformation was predicted by the two methods. Aqueous solution structure-characteristics were determined by Monte Carlo. Equilibration of conformers/tautomers through water-assisted double proton-relay is discussed. This mechanism is not viable, however, in non-protic solvents where the calculated potential of mean force curve does not predict remarkable solute dimerization and subsequent favorable orientation. PMID:25984602

  15. JMS Proxy and C/C++ Client SDK

    NASA Technical Reports Server (NTRS)

    Wolgast, Paul; Pechkam, Paul

    2007-01-01

    JMS Proxy and C/C++ Client SDK (JMS signifies "Java messaging service" and "SDK" signifies "software development kit") is a software package for developing interfaces that enable legacy programs (here denoted "clients") written in the C and C++ languages to communicate with each other via a JMS broker. This package consists of two main components: the JMS proxy server component and the client C library SDK component. The JMS proxy server component implements a native Java process that receives and responds to requests from clients. This component can run on any computer that supports Java and a JMS client. The client C library SDK component is used to develop a JMS client program running in each affected C or C++ environment, without need for running a Java virtual machine in the affected computer. A C client program developed by use of this SDK has most of the quality-of-service characteristics of standard Java-based client programs, including the following: Durable subscriptions; Asynchronous message receipt; Such standard JMS message qualities as "TimeToLive," "Message Properties," and "DeliveryMode" (as the quoted terms are defined in previously published JMS documentation); and Automatic reconnection of a JMS proxy to a restarted JMS broker.

  16. Reinterpretation of the Vibrational Spectroscopy of the Medicinal Bioinorganic Synthon c,c,t-[Pt(NH3)2Cl2(OH)2]

    PubMed Central

    Johnstone, Timothy C.

    2014-01-01

    The Pt(IV) complex c,c,t-[Pt(NH3)2Cl2(OH)2] is an important intermediate in the synthesis of Pt(IV) anticancer prodrugs and has been investigated as an anticancer agent in its own right. An analysis of the vibrational spectroscopy of this molecule was previously reported [Faggiani et al., 1982, Can. J. Chem. 60, 529] in which crystallographic determination of the structure of the complex permitted a site group approach. The space group, however, was incorrectly assigned. In the present study we have redetermined at high resolution crystal structures of c,c,t-[Pt(NH3)2Cl2(OH)2] and c,c,t-[Pt(NH3)2Cl2(OH)2]H2O2, which enable discussion of the effect of hydrogen bonding on the NH and OH vibrational bands. The correct crystallographic site symmetry of the platinum complex in the c,c,t-[Pt(NH3)2Cl2(OH)2] structure is employed to conduct a new vibrational analysis using both group theoretical and modern DFT methods. This analysis reveals the nature and symmetry of the missing band described in the original publication and suggests a possible explanation for its disappearance. PMID:24515615

  17. On the Relationship between the Enthalpy of Formation of Carbenes upon Cleavage of the Double Bond in Fluoroolefins and the Electron Density on the pi Bond: An Ab Initio Study

    SciTech Connect

    Borisov, Yurii A.; Garrett, Bruce C.; Kobanovskii, Y. A.; Bilera, I. V.; Buravtsev, N. N.

    2003-08-07

    In this study, we established a correlation between the enthalpy of cleavage of the C=C bond in fluorine-substituted olefins giving rise to two carbenes in the electronic ground state and the distribution of the electron density on this bond.

  18. Theoretical study of the bonding of Sc, Y, and La singly charged and dipositive ions to C2H2, C2H4, and C3H6

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.

    1991-01-01

    The interaction of the Sc and Y singly-charged and dipositive ions with C2H2, C2H4, and C3H6 is studied using electronic structure calculations that include high levels of electron correlation. These results are compared with comparable calculations performed previously for La(+) and La(2+). For C2H2 and C2H4, all three metal ions insert into the C-C pi bond, making a three-membered ring. The optimal structures for the MC3H6(+) ions all involve rearrangement to make a four-membered ring. The strength of the metal-ligand bond for the singly charged ions follows the order La greater than Sc equal to about Y. In contrast, the bonds involving the dipositive ions are electrostatic, so that the binding energy increases as the size of the ion decreases, leading to the trend Sc greater than Y greater than La.

  19. Pd loaded amphiphilic COF as catalyst for multi-fold Heck reactions, C-C couplings and CO oxidation

    PubMed Central

    Mullangi, Dinesh; Nandi, Shyamapada; Shalini, Sorout; Sreedhala, Sheshadri; Vinod, Chathakudath P.; Vaidhyanathan, Ramanathan

    2015-01-01

    COFs represent a class of polymers with designable crystalline structures capable of interacting with active metal nanoparticles to form excellent heterogeneous catalysts. Many valuable ligands/monomers employed in making coordination/organic polymers are prepared via Heck and C-C couplings. Here, we report an amphiphilic triazine COF and the facile single-step loading of Pd0 nanoparticles into it. An 1820% nano-Pd loading gives highly active composite working in open air at low concentrations (Conc. Pd(0) <0.05?mol%, average TON 1500) catalyzing simultaneous multiple site Heck couplings and C-C couplings using non-boronic acid substrates, and exhibits good recyclability with no sign of catalyst leaching. As an oxidation catalyst, it shows 100% conversion of CO to CO2 at 150?C with no loss of activity with time and between cycles. Both vapor sorptions and contact angle measurements confirm the amphiphilic character of the COF. DFT-TB studies showed the presence of Pd-triazine and Pd-Schiff bond interactions as being favorable. PMID:26057044

  20. Intramolecular, Pd/Cu-Co-catalyzed P-C Bond Cleavage and Addition onto an Alkyne: A Route to Benzophospholes.

    PubMed

    Zhou, Yang; Gan, Zhenjie; Su, Bo; Li, Jun; Duan, Zheng; Mathey, Franois

    2015-11-20

    Under Pd(II)/CuI cocatalysis, o-diarylphosphinophenylalkynes cyclize in boiling toluene via C-P bond cleavage and arylphosphination of the C?C bond. This protocol provides an unprecedented atom- and step-efficient access to optoelectronically and biologically interesting benzophospholes. PMID:26561234

  1. Functionalized olefin cross-coupling to construct carboncarbon bonds

    PubMed Central

    Lo, Julian C.; Gui, Jinghan; Yabe, Yuki; Pan, Chung-Mao; Baran, Phil S.

    2014-01-01

    Carboncarbon (CC) bonds form the backbone of many important molecules, including polymers, dyes, and pharmaceutical agents. The development of new methods to create these essential connections in a rapid and practical fashion has been the focus of numerous organic chemists. This endeavor heavily relies on the ability to form CC bonds in the presence of sensitive functional groups and congested structural environments. Here we report a fundamentally new chemical transformation that allows for the facile construction of highly substituted and uniquely functionalized CC bonds. Using a simple iron catalyst, an inexpensive silane, and a benign solvent under an ambient atmosphere, heteroatom-substituted olefins are easily merged with electron-deficient olefins to create molecular architectures that were previously difficult or impossible to access. More than sixty examples are presented with a wide array of substrates, demonstrating the unique chemoselectivity and mildness of this simple reaction. PMID:25519131

  2. Sensor/ROIC Integration using Oxide Bonding

    SciTech Connect

    Ye, Zhenyu; /Fermilab

    2009-02-01

    We explore the Ziptronix Direct Bond Interconnect (DBI) technology [2] for the integration of sensors and readout integrated circuits (ROICs) for high energy physics. The technology utilizes an oxide bond to form a robust mechanical connection between layers which serves to assist with the formation of metallic interlayer connections. We report on testing results of sample sensors bonded to ROICs and thinned to 100 {micro}m.

  3. Understanding Excitation Energy Transfer in Metalloporphyrin Heterodimers with Different Linkers, Bonding Structures and Geometries through Stimulated X-Ray Raman Spectroscopy

    PubMed Central

    Zhang, Yu; Biggs, Jason D.; Mukamel, Shaul

    2014-01-01

    We present simulations of stimulated X-ray Raman (SXRS) signals from covalent porphyrin heterodimers with different linkers, chemical bonding structures and geometries. The signals are interpreted in terms of valence electron wavepacket motion. One- and two-color SXRS signals can jointly indicate excitation energy transfer (EET) between the porphyrin monomers. It is shown that the SXRS signals provide a novel window into EET dynamics in multiporphyrin systems, and can be used as a powerful tool to monitor the subtle chemical environment which affects EET. PMID:25045204

  4. The use of exact Lamb waves modes for modeling the power and energy transduction of structurally bonded piezoelectric wafer active sensors

    NASA Astrophysics Data System (ADS)

    Lin, Bin; Giurgiutiu, Victor; Kamal, Ayman M.

    2012-04-01

    This paper presents a theoretical modeling of power and energy transduction of structurally-bonded piezoelectric wafer active sensors (PWAS) for structural health monitoring (SHM). After a literature review of the state of the art, we developed a model of power and energy transduction between the PWAS and a structure containing multimodal ultrasonic guided waves. The use of exact Lamb waves modes for power modeling is an extension of our previously presented simplified model that considered axial and flexural waves with low frequency approximation. The model assumptions include: (a) straight-crested multimodal ultrasonic guided wave propagation; (b) ideal bonding (pin-force) connection between PWAS and structure; (c) ideal excitation source at the transmitter PWAS and fully-resistive external load at the receiver PWAS. Frequency response functions are developed for voltage, current, complex power, active power, etc. Multimodal ultrasonic guided wave, normal mode expansion, electromechanical energy transformation of PWAS and structure were considered. The parametric study of PWAS size and impedance match gives the PWAS design guideline for PWAS sensing and power harvesting applications

  5. Wafer bonding for optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Wu, Yew-Chung Sermon

    A periodic GaAs wafer-bonded structure has been proposed for quasi-phase-matched (QPM) second harmonic generation (SHG). The basic bonding technology involves elevated temperatures and pressures, which can lead to unacceptable optical losses and poor device performance. Three sources of optical losses were first found in this study: (1) decomposition at the exposed surface, (2) interfacial defects between the bonded wafers, and (3) bulk defects within the wafers. Bulk and surface defects were studied by measuring the optical transmission through single GaAs. It was found that an increase in bonding temperature and/or time led to an increase in the bulk and surface defects. An increase in the free hole concentration (thermal conversion) is though to be the major cause of the optical losses by a free carrier absorption mechanism. Since it was difficult to eliminate free-carrier and interfacial defect losses once they have formed because of diffusion kinetic limitations, processing conditions that minimized their formation were sought. In contrast, defects on the external surfaces caused by arsenic depletion resulting from incongruent evaporation were easily eliminated by repolishing. Interfacial defects were studied by introducing artificial voids into the interface region by bonding topographically-patterned GaAs wafers to unpatterned wafers. We found that the filling of these artificial voids depended strongly on the magnitude of the height of the surface irregularities on the wafer interfaces, as well as on temperature and time. Typically, when bonding temperature and time were increased, the interfacial defect density decreased. After bonding, two kinds of features corresponding to the newly bonded areas were observed by IR microscopy. These two features, having diamond and dendrite geometries, were shown to depend on both surface energy anisotropy and growth rate anisotropy. An investigation of the relationship between bonding conditions (temperature, time and pressure) and optical losses (resulting from bulk, interfacial and surface defects), has led to the development of an optimized process for preparing periodic GaAs structures useful in quasi-phase-matched second harmonic generation applications. With this bonding process, low optical loss (~0.1-0.3%/interface) wafer-bonded (110) structures (containing up to 40 layers) for practical device applications were first fabricated in this study.

  6. Hydroxide-catalyzed bonding

    NASA Technical Reports Server (NTRS)

    Gwo, Dz-Hung (Inventor)

    2003-01-01

    A method of bonding substrates by hydroxide-catalyzed hydration/dehydration involves applying a bonding material to at least one surface to be bonded, and placing the at least one surface sufficiently close to another surface such that a bonding interface is formed between them. A bonding material of the invention comprises a source of hydroxide ions, and may optionally include a silicate component, a particulate filling material, and a property-modifying component. Bonding methods of the invention reliably and reproducibly provide bonds which are strong and precise, and which may be tailored according to a wide range of possible applications. Possible applications for bonding materials of the invention include: forming composite materials, coating substrates, forming laminate structures, assembly of precision optical components, and preparing objects of defined geometry and composition. Bonding materials and methods of preparing the same are also disclosed.

  7. H-H, C-H, and C-C NMR spin-spin coupling constants calculated by the FP-INDO method for aromatic hydrocarbons

    NASA Technical Reports Server (NTRS)

    Long, S. A. T.; Memory, J. D.

    1978-01-01

    The FP-INDO (finite perturbation-intermediate neglect of differential overlap) method is used to calculate the H-H, C-H, and C-C coupling constants in hertz for molecules of six different benzenoid hydrocarbons: benzene, naphthalene, biphenyl, anthracene, phenanthrene, and pyrene. The calculations are based on both the actual and the average molecular geometries. It is found that only the actual molecular geometries can always yield the correct relative order of values for the H-H coupling constants. For the calculated C-C coupling constants, as for the calculated C-H coupling constants, the signs are positive (negative) for an odd (even) number of bonds connecting the two nuclei. Agreements between the calculated and experimental values of the coupling constants for all six molecules are comparable to those reported previously for other molecules.

  8. IBM XL C/C++ Advanced Edition V8.0 for Linux Programming Guide

    E-print Network

    Hickman, Mark

    IBM XL C/C++ Advanced Edition V8.0 for Linux Programming Guide SC09-8014-00 #12;#12;IBM XL C/C++ Advanced Edition V8.0 for Linux Programming Guide SC09-8014-00 #12;Note! Before using this information) This edition applies to version 8.0 of IBM XL C/C++ Advanced Edition V8.0 for Linux (product number 5724-M16

  9. IBM XL C/C++ Advanced Edition V8.0 for Linux Language Reference

    E-print Network

    Hickman, Mark

    IBM XL C/C++ Advanced Edition V8.0 for Linux Language Reference SC09-8016-00 #12;#12;IBM XL C/C++ Advanced Edition V8.0 for Linux Language Reference SC09-8016-00 #12;Note! Before using this information (November, 2005) This edition applies to Version 8.0 of IBM XL C/C++ Advanced Edition for Linux (product

  10. IBM XL C/C++ Advanced Edition V8.0 for Linux Compiler Reference

    E-print Network

    Hickman, Mark

    IBM XL C/C++ Advanced Edition V8.0 for Linux Compiler Reference SC09-8013-00 #12;#12;IBM XL C/C++ Advanced Edition V8.0 for Linux Compiler Reference SC09-8013-00 #12;Note! Before using this information 2005 ) This edition applies to XL C/C++ Advanced Edition V8.0 for Linux (Program number 5724-M16

  11. IBM XL C/C++ Enterprise Edition V8.0 for AIX Programming Guide

    E-print Network

    Hickman, Mark

    IBM XL C/C++ Enterprise Edition V8.0 for AIX Programming Guide SC09-7996-00 #12;#12;IBM XL C/C++ Enterprise Edition V8.0 for AIX Programming Guide SC09-7996-00 #12;Note! Before using this information) This edition applies to version 8.0 of IBM XL C/C++ Enterprise Edition V8.0 for AIX (product number 5724-I12

  12. IBM XL C/C++ Enterprise Edition V8.0 for AIX Compiler Reference

    E-print Network

    Hickman, Mark

    IBM XL C/C++ Enterprise Edition V8.0 for AIX Compiler Reference SC09-7995-00 #12;#12;IBM XL C/C++ Enterprise Edition V8.0 for AIX Compiler Reference SC09-7995-00 #12;Note! Before using this information ) This edition applies to IBM XL C/C++ Enterprise Edition V8.0 for AIX (Program number 5724-M12) and to all

  13. IBM XL C/C++ Enterprise Edition V8.0 for AIX Language Reference

    E-print Network

    Hickman, Mark

    IBM XL C/C++ Enterprise Edition V8.0 for AIX Language Reference SC09-7998-00 #12;#12;IBM XL C/C++ Enterprise Edition V8.0 for AIX Language Reference SC09-7998-00 #12;Note! Before using this information (October, 2005) This edition applies to Version 8.0 of IBM XL C/C++ Enterprise Edition for AIX (product

  14. Highly Accurate CCSD(T) and DFTSAPT Stabilization Energies of H-Bonded and Stacked Structures of the Uracil Dimer

    SciTech Connect

    Pitonak, Michal; Riley, Kevin E.; Neogrady, Pavel; Hobza, Pavel

    2008-06-23

    The CCSD(T) interaction energies for the H-bonded and stacked structures of the uracil dimer are determined at the aug-cc-pVDZ and aug-cc-pVTZ levels. On the basis of these calculations we can construct the CCSD(T) interaction energies at the complete basis set (CBS) limit. The most accurate energies, based either on direct extrapolation of the CCSD(T) correlation energies obtained with the aug-cc-pVDZ and aug-cc-pVTZ basis sets or on the sum of extrapolated MP2 interaction energies (from aug-cc-pVTZ and aug-cc-pVQZ basis sets) and extrapolated ?CCSD(T) correction terms [difference between CCSD(T) and MP2 interaction energies] differ only slightly, which demonstrates the reliability and robustness of both techniques. The latter values, which represent new standards for the H-bonding and stacking structures of the uracil dimer, differ from the previously published data for the S22 set by a small amount. This suggests that interaction energies of the S22 set are generated with chemical accuracy. The most accurate CCSD(T)/CBS interaction energies are compared with interaction energies obtained from various computational procedures, namely the SCSMP2 (SCS: spin-component-scaled), SCS(MI)MP2 (MI: molecular interaction), MP3, dispersion-augmented DFT (DFTD), M062X, and DFTSAPT (SAPT: symmetry-adapted perturbation theory) methods. Among these techniques, the best results are obtained with the SCS(MI)MP2 method. Remarkably good binding energies are also obtained with the DFTSAPT method. Both DFT techniques tested yield similarly good interaction energies. The large magnitude of the stacking energy for the uracil dimer, compared to that of the benzene dimer, is explained by attractive electrostatic interactions present in the stacked uracil dimer. These interactions force both subsystems to approach each other and the dispersion energy benefits from a shorter intersystem separation.

  15. Using beryllium bonds to change halogen bonds from traditional to chlorine-shared to ion-pair bonds.

    PubMed

    Alkorta, Ibon; Elguero, Jos; M, Otilia; Yez, Manuel; Del Bene, Janet E

    2015-01-21

    Ab initio MP2/aug'-cc-pVTZ calculations have been carried out to investigate the structures, binding energies, and bonding characteristics of binary complexes HFBe:FCl, R2Be:FCl, and FCl:N-base, and of ternary complexes HFBe:FCl:N-base and R2Be:FCl:N-base for R = H, F, Cl; N-base = NH3, NHCH2, NCH. Dramatic synergistic cooperative effects have been found between the BeF beryllium bonds and the ClN halogen bonds in ternary complexes. The ClN traditional halogen bonds and the BeF beryllium bonds in binary complexes become significantly stronger in ternary complexes, while the F-Cl bond weakens. Charge-transfer from F to the empty p(?) orbital of Be leads to a bending of the XYBe molecule and a change in the hybridization of Be, which in the limit becomes sp(2). As a function of the intrinsic basicity of the nitrogen base and the intrinsic acidity of the Be derivative, the halogen-bond type evolves from traditional to chlorine-shared to ion-pair bonds. The mechanism by which an ion-pair complex is formed is similar to that involved in the dissociative proton attachment process. EOM-CCSD spin-spin coupling constants (1X)J(Cl-N) across the halogen bond in these complexes also provide evidence of the same evolution of the halogen-bond type. PMID:25486548

  16. Unusual nitrile-nitrile and nitrile-alkyne coupling of Fc-C?N and FC-C?C-C?N.

    PubMed

    Becker, Lisanne; Strehler, Frank; Korb, Marcus; Arndt, Perdita; Spannenberg, Anke; Baumann, Wolfgang; Lang, Heinrich; Rosenthal, Uwe

    2014-03-10

    The reactions of the Group?4 metallocene alkyne complexes, [Cp*2M(?2-Me3SiC2SiMe3)] (1?a: M=Ti, 1?b: M=Zr, Cp*=?5-pentamethylcyclopentadienyl), with the ferrocenyl nitriles, Fc-CN and Fc-C?C-C?N (Fc=Fe(?5-C5H5)(?5-C5H4)), is described. In case of Fc-C?N an unusual nitrilenitrile C-C homocoupling was observed and 1-metalla-2,5-diaza-cyclopenta-2,4-dienes (3?a, b) were obtained. As the first step of the reaction with 1?b, the nitrile was coordinated to give [Cp*2Zr(?2-Me3SiC2SiMe3)(N?C-Fc)] (2?b). The reactions with the 3-ferrocenyl-2-propyne-nitrile FcC?C-C?N lead to an alkynenitrile C-C coupling of two substrates and the formation of 1-metalla-2-aza-cyclopenta-2,4-dienes (4?a, b). For M=Zr, the compound is stabilized by dimerization as evidenced by single-crystal X-ray structure analysis. The electrochemical behavior of 3?a, b and 4?a, b was investigated, showing decomposition after oxidation, leading to different redox-active products. PMID:24615841

  17. Chirality transfer based on reversible C-C bond formation/breaking in nickel(II) complexes.

    PubMed

    Kawamoto, Tatsuya; Suzuki, Narumi; Ono, Takeshi; Gong, Dafei; Konno, Takumi

    2013-01-25

    The reaction of (1R)-(-)-myrtenal-derived benzothiazoline with nickel(II) acetate in ethanol exclusively gave a Schiff base-type nickel(II) complex having M helical configurational myrtenyl arms, which is reversibly converted to a non-innocent-type complex having additional S,S configurational asymmetric carbon centres. PMID:23090291

  18. An efficient and general route to reduced polypropionates via Zr-catalyzed asymmetric CC bond formation

    PubMed Central

    Negishi, Ei-ichi; Tan, Ze; Liang, Bo; Novak, Tibor

    2004-01-01

    An efficient and general method for the synthesis of reduced polypropionates has been developed through the application of asymmetric carboalumination of alkenes catalyzed by dichlorobis(1-neomenthylindenyl)zirconium [(NMI)2ZrCl2]. In this investigation, attention has been focused on those reduced polypropionates that are ?-monoheterofunctional and either ?-ethyl or ?-n-propyl. The reaction of 3-buten-1-ol with triethylaluminum (Et3Al) or tripropylaluminum (nPr3Al) in the presence of (NMI)2ZrCl2 and isobutylaluminoxane gave, after protonolysis, (R)-3-methyl-1-pentanol as well as (R)- and (S)-3-methyl-1-hexanols in 8892% yield in 9092% enantiomeric excess in one step. These 3-monomethyl-1-alkanols were then converted to two stereoisomers each of 2,4-dimethyl-1-hexanols and 2,4-dimethyl-1-heptanols via methylalumination catalyzed by (NMI)2ZrCl2 and methylaluminoxane followed by oxidation with O2. The four-step (or three-isolation-step) protocol provided syn-2,4-dimethyl-1-alkanols of ?98% stereoisomeric purity in ?50% overall yields, whereas (2S,4R)-2,4-dimethyl-1-hexanol of comparable purity was obtained in 40% overall yield. Commercial availability of (S)-2-methyl-1-butanol as a relatively inexpensive material suggested its use in the synthesis of (2S,4S)- and (2R,4S)-2,4-dimethyl-1-hexanols via a three-step protocol consisting of (i) iodination, (ii) zincation followed by Pd-catalyzed vinylation, and (iii) Zr-catalyzed methylalumination followed by oxidation with O2. This three-step protocol is iterative and applicable to the synthesis of reduced polypropionates containing three or more branching methyl groups, rendering this method for the synthesis of reduced polypropionates generally applicable. Its synthetic utility has been demonstrated by preparing the side chain of zaragozic acid A and the C11C20 fragment of antibiotics TMC-151 AF. PMID:15073327

  19. Hapalindole/Ambiguine Biogenesis Is Mediated by a Cope Rearrangement, C-C Bond-Forming Cascade.

    PubMed

    Li, Shasha; Lowell, Andrew N; Yu, Fengan; Raveh, Avi; Newmister, Sean A; Bair, Nathan; Schaub, Jeffrey M; Williams, Robert M; Sherman, David H

    2015-12-16

    Hapalindoles are bioactive indole alkaloids with fascinating polycyclic ring systems whose biosynthetic assembly mechanism has remained unknown since their initial discovery in the 1980s. In this study, we describe the fam gene cluster from the cyanobacterium Fischerella ambigua UTEX 1903 encoding hapalindole and ambiguine biosynthesis along with the characterization of two aromatic prenyltransferases, FamD1 and FamD2, and a previously undescribed cyclase, FamC1. These studies demonstrate that FamD2 and FamC1 act in concert to form the tetracyclic core ring system of the hapalindoles from cis-indole isonitrile and geranyl pyrophosphate through a presumed biosynthetic Cope rearrangement and subsequent 6-exo-trig cyclization/electrophilic aromatic substitution reaction. PMID:26629885

  20. Probing o-diphenylphosphanyl benzoate (o-DPPB)-directed C-C bond formation: total synthesis of dictyostatin.

    PubMed

    Wnsch, Sebastian; Breit, Bernhard

    2015-02-01

    Herein, we report a robust total synthesis of dictyostatin. This polyketide natural product has attracted much attention because of its impressive antiproliferative activity against several human cancer-cell lines. We accomplished its synthesis in a highly convergent manner from three fragments of equal complexity, which were prepared on multigram scale. The southern and northwestern subunits were constructed through application of our o-DPPB-directed hydroformylation and allylic substitution methodology, respectively. These methods generated the C6 and C14 stereocenters of dictyostatin with good diastereoselectivities and simultaneously allowed further elaboration of the fragments by Wittig olefination and Sharpless asymmetric epoxidation, respectively. The compelling performance of the hydroformylation and allylic substitution with regard to practicability, selectivity, and scale underline their value for the construction of propionate motifs. PMID:25524890

  1. Cyanide-catalyzed C-C bond formation: synthesis of novel compounds, materials and ligands for homogeneous catalysis

    E-print Network

    Reich, Blair Jesse Ellyn

    2007-04-25

    under aerobic conditions to yield conjugated oligoketimines and polyketimines with unprecedented structure and molecular weight (DP = 2 - 23, ~700 -8200 g/mol). The ?±- diimine linkage was established based on IR spectroscopy, NMR spectroscopy, size...

  2. Topotactic elimination of water across a C-C ligand bond in a dense 3-D metal-organic framework.

    PubMed

    Yeung, Hamish H-M; Kosa, Monica; Griffin, John M; Grey, Clare P; Major, Dan T; Cheetham, Anthony K

    2014-11-11

    Upon heating, lithium L-malate undergoes topotactic dehydration to form a phase containing the unsaturated fumarate ligand, in which the original 3-D framework remains intact. Insight into this unusual transformation has been obtained by single crystal X-ray diffraction, MAS-NMR, in situ powder X-ray diffraction and DFT calculations. PMID:25232700

  3. C-C Bond Formation via Copper-Catalyzed Conjugate Addition Reactions to Enones in Water at Room Temperature

    PubMed Central

    Lipshutz, Bruce H.; Huang, Shenlin; Leong, Wendy Wen Yi; Isley, Nicholas A.

    2013-01-01

    Conjugate addition reactions to enones can now be done in water at room temperature with in situ-generated organocopper reagents. Mixing an enone, zinc powder, TMEDA, and an alkyl halide in a micellar environemnt containing catalytic amounts of Cu(I), Ag(I), and Au(III), leads to 1,4-adducts in good isolated yields: no organometallic precursor is involved. PMID:23190029

  4. Multicomponent synthesis of chiral bidentate unsymmetrical unsaturated N-heterocyclic carbenes: copper-catalyzed asymmetric C-C bond formation.

    PubMed

    Jahier-Diallo, Claire; Morin, Marie S T; Queval, Pierre; Rouen, Mathieu; Artur, Isabelle; Querard, Pierre; Toupet, Loic; Crvisy, Christophe; Basl, Olivier; Mauduit, Marc

    2015-01-12

    A multicomponent strategy was applied to the synthesis of chiral bidentate unsaturated hydroxyalkyl- and carboxyalkyl-N-heterocyclic carbene (NHC) precursors. The newly developed low-cost chiral ligands derived from amino alcohols and amino acids were evaluated in copper-catalyzed asymmetric conjugated addition and asymmetric allylic alkylation, which afforded the desired tertiary and quaternary carbon stereocenters with excellent regio- and enantioselectivities (up to 99:1 e.r.). PMID:25421857

  5. Palladium-catalyzed enolate arylation as a key C-C bond-forming reaction for the synthesis of isoquinolines.

    PubMed

    Pilgrim, Ben S; Gatland, Alice E; Esteves, Carlos H A; McTernan, Charlie T; Jones, Geraint R; Tatton, Matthew R; Procopiou, Panayiotis A; Donohoe, Timothy J

    2016-01-21

    The palladium-catalyzed coupling of an enolate with an ortho-functionalized aryl halide (an ?-arylation) furnishes a protected 1,5-dicarbonyl moiety that can be cyclized to an isoquinoline with a source of ammonia. This fully regioselective synthetic route tolerates a wide range of substituents, including those that give rise to the traditionally difficult to access electron-deficient isoquinoline skeletons. These two synthetic operations can be combined to give a three-component, one-pot isoquinoline synthesis. Alternatively, cyclization of the intermediates with hydroxylamine hydrochloride engenders direct access to isoquinoline N-oxides; and cyclization with methylamine, gives isoquinolinium salts. Significant diversity is available in the substituents at the C4 position in four-component, one-pot couplings, by either trapping the in situ intermediate after ?-arylation with carbon or heteroatom-based electrophiles, or by performing an ?,?-heterodiarylation to install aryl groups at this position. The ?-arylation of nitrile and ester enolates gives access to 3-amino and 3-hydroxyisoquinolines and the ?-arylation of tert-butyl cyanoacetate followed by electrophile trapping, decarboxylation and cyclization, C4-functionalized 3-aminoisoquinolines. An oxime directing group can be used to direct a C-H functionalization/bromination, which allows monofunctionalized rather than difunctionalized aryl precursors to be brought through this synthetic route. PMID:26632484

  6. Expanding the substrate scope in palladium-catalyzed C-N and C-C bond-forming reactions

    E-print Network

    Anderson, Kevin William

    2006-01-01

    Chapter 1. The first detailed study of the palladium-catalyzed amination of aryl nonaflates is reported. Use of bulky electron-rich monophosphinobiaryl ligands or BINAP allow for the catalytic amination of electron-rich ...

  7. Thermochemistry of C7H16 to C10H22 alkane isomers: primary, secondary, and tertiary C-H bond dissociation energies and effects of branching.

    PubMed

    Hudzik, Jason M; Bozzelli, Joseph W; Simmie, John M

    2014-10-01

    Standard enthalpies of formation (?Hf298) of methyl, ethyl, primary and secondary propyl, and n-butyl radicals are evaluated and used in work reactions to determine internal consistency. They are then used to calculate the enthalpy of formation for the tert-butyl radical. Other thermochemical properties including standard entropies (S(T)), heat capacities (Cp(T)), and carbon-hydrogen bond dissociation energies (C-H BDEs) are reported for n-pentane, n-heptane, 2-methylhexane, 2,3-dimethylpentane, and several branched higher carbon number alkanes and their radicals. ?Hf298 and C-H BDEs are calculated using isodesmic work reactions at the B3LYP (6-31G(d,p) and 6-311G(2d,2p) basis sets), CBS-QB3, CBS-APNO, and G3MP2B3 levels of theory. Structures, moments of inertia, vibrational frequencies, and internal rotor potentials are calculated at the B3LYP/6-31G(d,p) level for contributions to entropy and heat capacities. Enthalpy calculations for these hydrocarbon radical species are shown to have consistency with the CBS-QB3 and CBS-APNO methods using all work reactions. Our recommended ideal gas phase ?Hf298 values are from the average of all CBS-QB3, CBS-APNO, and for G3MP2B3, only where the reference and target radical are identical types, and are compared with literature values. Calculated values show agreement between the composite calculation methods and the different work reactions. Secondary and tertiary C-H bonds in the more highly branched alkanes are shown to have bond energies that are several kcal mol(-1) lower than the BDEs in corresponding smaller molecules often used as reference species. Entropies and heat capacities are calculated and compared to literature values (when available) when all internal rotors are considered. PMID:25180943

  8. Identification of the Chemical Bonding Prompting Adhesion of a-C:H Thin Films on Ferrous Alloy Intermediated by a SiCx:H Buffer Layer.

    PubMed

    Cemin, F; Bim, L T; Leidens, L M; Morales, M; Baumvol, I J R; Alvarez, F; Figueroa, C A

    2015-07-29

    Amorphous carbon (a-C) and several related materials (DLCs) may have ultralow friction coefficients that can be used for saving-energy applications. However, poor chemical bonding of a-C/DLC films on metallic alloys is expected, due to the stability of carbon-carbon bonds. Silicon-based intermediate layers are employed to enhance the adherence of a-C:H films on ferrous alloys, although the role of such buffer layers is not yet fully understood in chemical terms. The chemical bonding of a-C:H thin films on ferrous alloy intermediated by a nanometric SiCx:H buffer layer was analyzed by X-ray photoelectron spectroscopy (XPS). The chemical profile was inspected by glow discharge optical emission spectroscopy (GDOES), and the chemical structure was evaluated by Raman and Fourier transform infrared spectroscopy techniques. The nature of adhesion is discussed by analyzing the chemical bonding at the interfaces of the a-C:H/SiCx:H/ferrous alloy sandwich structure. The adhesion phenomenon is ascribed to specifically chemical bonding character at the buffer layer. Whereas carbon-carbon (C-C) and carbon-silicon (C-Si) bonds are formed at the outermost interface, the innermost interface is constituted mainly by silicon-iron (Si-Fe) bonds. The oxygen presence degrades the adhesion up to totally delaminate the a-C:H thin films. The SiCx:H deposition temperature determines the type of chemical bonding and the amount of oxygen contained in the buffer layer. PMID:26135943

  9. Pressureless Bonding Using Sputtered Ag Thin Films

    NASA Astrophysics Data System (ADS)

    Oh, Chulmin; Nagao, Shijo; Suganuma, Katsuaki

    2014-12-01

    To improve the performance and reliability of power electronic devices, particularly those built around next-generation wide-bandgap semiconductors such as SiC and GaN, the bonding method used for packaging must change from soldering to solderless technology. Because traditional solders are problematic in the harsh operating conditions expected for emerging high-temperature power devices, we propose a new bonding method in this paper, namely a pressureless, low-temperature bonding process in air, using abnormal grain growth on sputtered Ag thin films to realize extremely high temperature resistance. To investigate the mechanisms of this bonding process, we characterized the microstructural changes in the Ag films over various bonding temperatures and times. We measured the bonding properties of the specimens by a die-shear strength test, as well as by x-ray diffraction measurements of the residual stress in the Ag films to show how the microstructural developments were essential to the bonding technology. Sound bonds with high die strength can be achieved only with abnormal grain growth at optimum bonding temperature and time. Pressureless bonding allows for production of reliable high-temperature power devices for a wide variety of industrial, energy, and environmental applications.

  10. 25 CFR 225.30 - Bonds.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS OIL AND GAS, GEOTHERMAL, AND SOLID MINERALS... Circular No. 570). (b) An operator may file a $75,000 bond for all geothermal, mining, or oil and gas... operator may file a $150,000 bond for full nationwide coverage to cover all geothermal or oil and...

  11. 25 CFR 225.30 - Bonds.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS OIL AND GAS, GEOTHERMAL, AND SOLID MINERALS... Circular No. 570). (b) An operator may file a $75,000 bond for all geothermal, mining, or oil and gas... operator may file a $150,000 bond for full nationwide coverage to cover all geothermal or oil and...

  12. 25 CFR 225.30 - Bonds.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS OIL AND GAS, GEOTHERMAL, AND SOLID MINERALS... Circular No. 570). (b) An operator may file a $75,000 bond for all geothermal, mining, or oil and gas... operator may file a $150,000 bond for full nationwide coverage to cover all geothermal or oil and...

  13. 25 CFR 227.8 - Bonds.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 25 Indians 1 2011-04-01 2011-04-01 false Bonds. 227.8 Section 227.8 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF CERTAIN LANDS IN WIND RIVER INDIAN RESERVATION, WYOMING, FOR OIL AND GAS MINING How to Acquire Leases 227.8 Bonds. The provisions of 211.6...

  14. 25 CFR 227.8 - Bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Bonds. 227.8 Section 227.8 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF CERTAIN LANDS IN WIND RIVER INDIAN RESERVATION, WYOMING, FOR OIL AND GAS MINING How to Acquire Leases 227.8 Bonds. The provisions of 211.6...

  15. 25 CFR 227.8 - Bonds.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 25 Indians 1 2012-04-01 2011-04-01 true Bonds. 227.8 Section 227.8 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF CERTAIN LANDS IN WIND RIVER INDIAN RESERVATION, WYOMING, FOR OIL AND GAS MINING How to Acquire Leases 227.8 Bonds. The provisions of 211.6...

  16. 25 CFR 216.8 - Performance bond.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS SURFACE EXPLORATION, MINING, AND... mining plan, the operator shall be required to file a suitable performance bond of not less than $2,000..., or contract, and the exploration or mining plan as approved, amended or supplemented. The bond...

  17. 25 CFR 216.8 - Performance bond.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS SURFACE EXPLORATION, MINING, AND... mining plan, the operator shall be required to file a suitable performance bond of not less than $2,000..., or contract, and the exploration or mining plan as approved, amended or supplemented. The bond...

  18. 25 CFR 216.8 - Performance bond.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS SURFACE EXPLORATION, MINING, AND... mining plan, the operator shall be required to file a suitable performance bond of not less than $2,000..., or contract, and the exploration or mining plan as approved, amended or supplemented. The bond...

  19. 25 CFR 216.8 - Performance bond.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS SURFACE EXPLORATION, MINING, AND... mining plan, the operator shall be required to file a suitable performance bond of not less than $2,000..., or contract, and the exploration or mining plan as approved, amended or supplemented. The bond...

  20. 25 CFR 216.8 - Performance bond.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS SURFACE EXPLORATION, MINING, AND... mining plan, the operator shall be required to file a suitable performance bond of not less than $2,000..., or contract, and the exploration or mining plan as approved, amended or supplemented. The bond...

  1. Twisting of glycosidic bonds by hydrolases

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Patterns of scissile bond twisting have been found in crystal structures of glycoside hydrolases (GHs) that are complexed with substrates and inhibitors. To estimate the increased potential energy in the substrates that results from this twisting, we have plotted torsion angles for the scissile bond...

  2. HYDROGEN BONDING IN THE METHANOL DIMER

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this work, two methanol molecules are placed in different arrangements to study hydrogen bonding in carbohydrate materials such as cellulose. Energy was calculated as a function of both hydrogen bond length and angle over wide ranges, using quantum mechanics (QM). The QM wavefunctions are analyze...

  3. 25 CFR 215.13 - Bond.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 25 Indians 1 2011-04-01 2011-04-01 false Bond. 215.13 Section 215.13 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEAD AND ZINC MINING OPERATIONS AND LEASES, QUAPAW AGENCY 215.13 Bond. Every mineral lease made and entered into under the regulations in this part, by...

  4. 25 CFR 215.13 - Bond.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 25 Indians 1 2013-04-01 2013-04-01 false Bond. 215.13 Section 215.13 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEAD AND ZINC MINING OPERATIONS AND LEASES, QUAPAW AGENCY 215.13 Bond. Every mineral lease made and entered into under the regulations in this part, by...

  5. 25 CFR 225.30 - Bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS OIL AND GAS, GEOTHERMAL, AND SOLID MINERALS... Circular No. 570). (b) An operator may file a $75,000 bond for all geothermal, mining, or oil and gas... operator may file a $150,000 bond for full nationwide coverage to cover all geothermal or oil and...

  6. 25 CFR 211.24 - Bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF TRIBAL LANDS FOR MINERAL DEVELOPMENT...,000 bond for all geothermal, mining, or oil and gas leases, permits, or assignments in any one State...,000 bond for full nationwide coverage to cover all geothermal or oil and gas leases, permits,...

  7. 25 CFR 225.30 - Bonds.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS OIL AND GAS, GEOTHERMAL, AND SOLID MINERALS... Circular No. 570). (b) An operator may file a $75,000 bond for all geothermal, mining, or oil and gas... operator may file a $150,000 bond for full nationwide coverage to cover all geothermal or oil and...

  8. The influence of hydrogen bonding on the dielectric constant and the piezoelectric energy harvesting performance of hydrated metal salt mediated PVDF films.

    PubMed

    Jana, Santanu; Garain, Samiran; Sen, Shrabanee; Mandal, Dipankar

    2015-07-14

    Polyvinylidene fluoride (PVDF) films are filled with various mass fractions (wt%) of hydrated metal salt (MgCl26H2O) (Mg-salt) to fabricate high performance piezoelectric energy harvesters (PEHs). They deliver up to 4 V of open circuit voltage by simply repeated human finger imparting (under a pressure of ?4.45 kPa) and also generate sufficient power to turn on at least ten commercial blue light emitting diodes (LEDs) instantly. The enhanced piezo-response is attributed to the combined effect of the change in the inherent dipole moment of the electroactive phase containing PVDF itself and H-bonding arising between the Mg-salt filler and PVDF via electrostatic interactions. Furthermore, it also successfully charged the capacitors, signifying practical applicability as a piezoelectric based energy harvester power source. UV-visible optical absorption spectral analysis revealed the possibility to estimate a change in the optical band gap value at different concentrations of Mg-salt filler added PVDF films that possess a useful methodology where the Mg-salt can be used as an optical probe. In addition dielectric properties have been studied to understand the role of molecular kinetic and interfacial polarization occurs in H-bond PVDF films at different applied frequencies at room temperature. PMID:26077827

  9. Influence of chlorine substitution on intramolecular hydrogen bond energy and ESIPT barrier: Experimental and theoretical measurements on the photophysics of 3,5-dichlorosalicylic acid

    NASA Astrophysics Data System (ADS)

    Paul, Bijan Kumar; Samanta, Anuva; Guchhait, Nikhil

    2010-08-01

    The effect of chlorine atom on the intramolecular hydrogen bond strength and excited state proton transfer barrier in pharmaceutically important chloro-substituted derivative of salicylic acid viz., 3,5-dichlorosalicylic acid (3,5DCSA) has been explored through steady-state absorption, emission and time-resolved fluorescence spectroscopy. Stokes shifted emission band with negligible solvent polarity dependency corresponds to the spectroscopic signature of excited state intramolecular proton transfer (ESIPT) reaction. The spectral signature was compared with its parent molecule salicylic acid (SA) and 5-chlorosalicylic acid (5ClSA). Quantum chemical calculations by ab initio Hartree-Fock (HF) and Density Functional Theory (DFT) methods have been fruitfully employed to correlate experimental findings. Calculated S0 and S1 states potential energy surfaces across the proton transfer co-ordinate substantiates the experimental evidence for the occurrence of ESIPT process and negates the ground state intramolecular proton transfer (GSIPT) reaction. Weakening of intramolecular hydrogen bond (IMHB) energy and subsequent enhancement of barrier to ESIPT reaction in 3,5DCSA as compared to SA and 5ClSA appears to be a reflection of conjugate impact of electron withdrawing inductive and electron donating resonance effects of chlorine substitutions depending on its location on the aromatic benzene nucleus.

  10. Detection of Alpha Particles and Low Energy Gamma Rays by Thermo-Bonded Micromegas in Xenon Gas

    E-print Network

    Yuehuan Wei; Liang Guan; Zhiyong Zhang; Qing Lin; Xiaolian Wang; Kaixuan Ni; Tianchi Zhao

    2013-08-09

    Micromegas is a type of micro-pattern gaseous detector currently under R&D for applications in rare event search experiments. Here we report the performance of a Micromegas structure constructed with a micromesh thermo-bonded to a readout plane, motivated by its potential application in two-phase xenon detectors for dark matter and neutrinoless double beta decay experiments. The study is carried out in pure xenon at room temperature. Measurements with alpha particles from the Americium-241 source showed that gas gains larger than 200 can be obtained at xenon pressure up to 3 atm. Gamma rays down to 8 keV were observed with such a device.

  11. Detection of Alpha Particles and Low Energy Gamma Rays by Thermo-Bonded Micromegas in Xenon Gas

    E-print Network

    Wei, Yuehuan; Zhang, Zhiyong; Lin, Qing; Wang, Xiaolian; Ni, Kaixuan; Zhao, Tianchi

    2013-01-01

    Micromegas is a type of micro-pattern gaseous detector currently under R&D for applications in rare event search experiments. Here we report the performance of a Micromegas structure constructed with a micromesh thermo-bonded to a readout plane, motivated by its potential application in two-phase xenon detectors for dark matter and neutrinoless double beta decay experiments. The study is carried out in pure xenon at room temperature. Measurements with alpha particles from the Americium-241 source showed that gas gains larger than 200 can be obtained at xenon pressure up to 3 atm. Gamma rays down to 8 keV were observed with such a device.

  12. Essays on corporate bonds

    E-print Network

    Bao, Jack (Jack C.)

    2009-01-01

    This thesis consists of three empirical essays on corporate bonds, examining the role of both credit risk and liquidity. In the first chapter, I test the ability of structural models of default to price corporate bonds in ...

  13. Overview of C/C-SiC Composite Development for the Orion Launch Abort System

    NASA Technical Reports Server (NTRS)

    Allen, Lee R.; Valentine, Peter G.; Schofield, Elizabeth S.; Beshears, Ronald D.; Coston, James E.

    2012-01-01

    Past and present efforts by the authors to further understanding of the ceramic matrix composite (CMC) material used in the valve components of the Orion Launch Abort System (LAS) Attitude Control Motor (ACM) will be presented. The LAS is designed to quickly lift the Orion Crew Exploration Vehicle (CEV) away from its launch vehicle in emergency abort scenarios. The ACM is a solid rocket motor which utilizes eight throttleable nozzles to maintain proper orientation of the CEV during abort operations. Launch abort systems have not been available for use by NASA on manned launches since the last Apollo ]Saturn launch in 1975. The CMC material, carbon-carbon/silicon-carbide (C/C-SiC), is manufactured by Fiber Materials, Inc. and consists of a rigid 4-directional carbon-fiber tow weave reinforced with a mixed carbon plus SiC matrix. Several valve and full system (8-valve) static motor tests have been conducted by the motor vendor. The culmination of these tests was the successful flight test of the Orion LAS Pad Abort One (PA ]1) vehicle on May 6, 2010. Due to the fast pace of the LAS development program, NASA Marshall Space Flight Center assisted the LAS community by performing a series of material and component evaluations using fired hardware from valve and full ]system development motor tests, and from the PA-1 flight ACM motor. Information will be presented on the structure of the C/C-SiC material, as well as the efficacy of various non ]destructive evaluation (NDE) techniques, including but not limited to: radiography, computed tomography, nanofocus computed tomography, and X-ray transmission microscopy. Examinations of the microstructure of the material via scanning electron microscopy and energy dispersive spectroscopy will also be discussed. The findings resulting from the subject effort are assisting the LAS Project in risk assessments and in possible modifications to the final ACM operational design.

  14. Diffusion bonding aeroengine components

    NASA Astrophysics Data System (ADS)

    Fitzpatrick, G. A.; Broughton, T.

    1988-10-01

    The use of diffusion bonding processes at Rolls-Royce for the manufacture of titanium-alloy aircraft engine components and structures is described. A liquid-phase diffusion bonding process called activated diffusion bonding has been developed for the manufacture of the hollow titanium wide chord fan blade. In addition, solid-state diffusion bonding is being used in the manufacture of hollow vane/blade airfoil constructions mainly in conjunction with superplastic forming and hot forming techniques.

  15. Catalytic ?-activation of carbon-carbon triple bonds: reactions of propargylic alcohols and alkynes.

    PubMed

    Kumar, Rapolu Kiran; Bi, Xihe

    2016-01-01

    The majority reactions of alkynes in the literature are reported to proceed via either structural ?-activation or catalytic ?-activation of C[triple bond, length as m-dash]C bonds. We skillfully designed novel methods for the catalytic ?-activation of C[triple bond, length as m-dash]C bonds of alkynyl compounds. For terminal alkynyl compounds, ?-activation was achieved by silver(i)-catalyzed C-H functionalization. Whereas ?-activation of internal alkynes was accomplished by the generation of propargylic cations from propargylic alcohols under Lewis-acid catalysis. These ?-activated species have been successfully used for new C-C and C-heteroatom bond formation reactions. Plausible reaction pathways were proposed based on typical control experiments to help the readers to gain insights into reactions and for further discovery of new reactions based on this concept of catalytic ?-activation of C[triple bond, length as m-dash]C bonds. PMID:26658835

  16. Acrylic mechanical bond tests

    SciTech Connect

    Wouters, J.M.; Doe, P.J.

    1991-02-01

    The tensile strength of bonded acrylic is tested as a function of bond joint thickness. 0.125 in. thick bond joints were found to posses the maximum strength while the acceptable range of joints varied from 0.063 in. to almost 0.25 in. Such joints are used in the Sudbury Neutrino Observatory.

  17. Testing of DLR C/C-SiC for HIFiRE 8 Scramjet Combustor

    NASA Technical Reports Server (NTRS)

    Glass, David E.; Capriotti, Diego P.; Reimer, Thomas; Kutemeyer, Marius; Smart, Michael

    2013-01-01

    Ceramic Matrix Composites (CMCs) have been proposed for hot structures in scramjet combustors. Previous studies have calculated significant weight savings by utilizing CMCs (active and passive) versus actively cooled metallic scramjet structures. Both a C/C and a C/C-SiC material system fabricated by DLR (Stuttgart, Germany) are being considered for use in a passively cooled combustor design for HIFiRE 8, a joint Australia / AFRL hypersonic flight program, expected to fly at Mach 7 for approximately 30 sec, at a dynamic pressure of 55 kPa. Flat panels of the DLR C/C and the C/C-SiC were tested in the NASA Langley Direct Connect Rig (DCR) at Mach 5 and Mach 6 enthalpy for several minutes. Gaseous hydrogen fuel was used to fuel the scramjet combustor. The test panels were instrumented with embedded Type K and Type S thermocouples. Zirconia felt insulation was used in some of the tests to increase the surface temperature of the C/C-SiC panel for approximately 350degF. The final C/C-SiC panel was tested for 3 cycles totaling over 135 sec at Mach 6 enthalpy. Slightly more erosion was observed on the C/C panel than the C/C-SiC panels, but both material systems demonstrated acceptable recession performance for the HIFiRE 8 flight.

  18. MPI-CHECK for C/C++ MPI Programs Pavel Kru sina and Glenn R. Luecke

    E-print Network

    Luecke, Glenn R.

    MPI-CHECK for C/C++ MPI Programs Pavel Kru#20;sina and Glenn R. Luecke #3; 291 Durham Center, Iowa manager. However, the current version of Umpire requires that a shared memory parallel computer is being C/C++ program Instrumentation and compilation Results MPI processes MPI-CHECK server Figure 1: MPI

  19. 77 FR 10004 - C$ cMoney, Inc.; Order of Suspension of Trading

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-21

    ... From the Federal Register Online via the Government Printing Office SECURITIES AND EXCHANGE COMMISSION C$ cMoney, Inc.; Order of Suspension of Trading February 16, 2012. It appears to the Securities... securities of C$ cMoney, Inc. (``cMoney'') because of questions regarding the accuracy of assertions by...

  20. Excitation energies with linear response density matrix functional theory along the dissociation coordinate of an electron-pair bond in N-electron systems.

    PubMed

    van Meer, R; Gritsenko, O V; Baerends, E J

    2014-01-14

    Time dependent density matrix functional theory in its adiabatic linear response formulation delivers exact excitation energies ?? and oscillator strengths f? for two-electron systems if extended to the so-called phase including natural orbital (PINO) theory. The Lo?wdin-Shull expression for the energy of two-electron systems in terms of the natural orbitals and their phases affords in this case an exact phase-including natural orbital functional (PILS), which is non-primitive (contains other than just J and K integrals). In this paper, the extension of the PILS functional to N-electron systems is investigated. With the example of an elementary primitive NO functional (BBC1) it is shown that current density matrix functional theory ground state functionals, which were designed to produce decent approximations to the total energy, fail to deliver a qualitatively correct structure of the (inverse) response function, due to essential deficiencies in the reconstruction of the two-body reduced density matrix (2RDM). We now deduce essential features of an N-electron functional from a wavefunction Ansatz: The extension of the two-electron Lo?wdin-Shull wavefunction to the N-electron case informs about the phase information. In this paper, applications of this extended Lo?wdin-Shull (ELS) functional are considered for the simplest case, ELS(1): one (dissociating) two-electron bond in the field of occupied (including core) orbitals. ELS(1) produces high quality ??(R) curves along the bond dissociation coordinate R for the molecules LiH, Li2, and BH with the two outer valence electrons correlated. All of these results indicate that response properties are much more sensitive to deficiencies in the reconstruction of the 2RDM than the ground state energy, since derivatives of the functional with respect to both the NOs and the occupation numbers need to be accurate. PMID:24437859

  1. Excitation energies with linear response density matrix functional theory along the dissociation coordinate of an electron-pair bond in N-electron systems

    NASA Astrophysics Data System (ADS)

    van Meer, R.; Gritsenko, O. V.; Baerends, E. J.

    2014-01-01

    Time dependent density matrix functional theory in its adiabatic linear response formulation delivers exact excitation energies ?? and oscillator strengths f? for two-electron systems if extended to the so-called phase including natural orbital (PINO) theory. The Lwdin-Shull expression for the energy of two-electron systems in terms of the natural orbitals and their phases affords in this case an exact phase-including natural orbital functional (PILS), which is non-primitive (contains other than just J and K integrals). In this paper, the extension of the PILS functional to N-electron systems is investigated. With the example of an elementary primitive NO functional (BBC1) it is shown that current density matrix functional theory ground state functionals, which were designed to produce decent approximations to the total energy, fail to deliver a qualitatively correct structure of the (inverse) response function, due to essential deficiencies in the reconstruction of the two-body reduced density matrix (2RDM). We now deduce essential features of an N-electron functional from a wavefunction Ansatz: The extension of the two-electron Lwdin-Shull wavefunction to the N-electron case informs about the phase information. In this paper, applications of this extended Lwdin-Shull (ELS) functional are considered for the simplest case, ELS(1): one (dissociating) two-electron bond in the field of occupied (including core) orbitals. ELS(1) produces high quality ??(R) curves along the bond dissociation coordinate R for the molecules LiH, Li2, and BH with the two outer valence electrons correlated. All of these results indicate that response properties are much more sensitive to deficiencies in the reconstruction of the 2RDM than the ground state energy, since derivatives of the functional with respect to both the NOs and the occupation numbers need to be accurate.

  2. Cu6Sn5-TiC-C nanocomposite anodes for high-performance sodium-ion batteries

    NASA Astrophysics Data System (ADS)

    Kim, Il Tae; Allcorn, Eric; Manthiram, Arumugam

    2015-05-01

    Cu6Sn5 alloy nanoparticles dispersed in a TiC and C conductive matrix have been developed via high energy mechanical milling (HEMM), and the resulting Cu6Sn5-TiC-C nanocomposite has been assessed as anodes for sodium-ion batteries. Composite anodes of Sn-C exhibit poor cyclic performance even with the introduction of 2 vol. % fluoroethylene carbonate (FEC) additive into the electrolyte. In contrast, Cu6Sn5-TiC-C nanocomposite anodes exhibit stable cycle life corresponding to a capacity retention of ?80% at 40 cycles and high-rate performance with a capacity retention of ?62% at 3000 mA g-1. These superior performance metrics is ascribed to the well-developed electrochemically active nanocrystalline material (Cu6Sn5) as well as a hybrid conductive matrix (TiC and C). The incorporation of 2 vol. % FEC additive into the electrolyte further improves the performance of Cu6Sn5-TiC-C nanocomposite to display a capacity retention of ?94% at 250 cycles and high-rate capacity retention of ?82% at 5000 mA g-1, which are attributed to the formation of a thin and stable SEI layer in presence of FEC.

  3. High-Performance Zn-TiC-C Nanocomposite Alloy Anode with Exceptional Cycle Life for Lithium-Ion Batteries.

    PubMed

    Kim, Sang-Ok; Manthiram, Arumugam

    2015-07-15

    A Zn-based nanocomposite has been prepared through a facile, low-cost high-energy mechanochemical process and employed as an anode material for lithium-ion batteries. Structural characterization reveals that the micrometer-sized Zn-TiC-C nanocomposite is composed of Zn nanocrystals uniformly dispersed in a multifunctional TiC and conductive carbon matrix with a tap density of 1.3 g cm(-3). The Zn-TiC-C nanocomposite exhibits high reversible volumetric capacity (468 mA h cm(-3)), excellent cyclability over 800 cycles (79.2% retention), and good rate performance up to 12.5C (75% of its capacity at 0.25C rate). The enhanced electrochemical performance is mainly due to the presence of the well-mixed TiC+C matrix that plays an important role in providing high conductivity as well as mechanical buffer that mitigates the huge volume expansion and contraction during prolonged cycling. In addition, it prevents the particle growth by uniformly dispersing nanosized Zn within itself during cycling, maintaining high utilization (?100%) and fast reaction kinetics of Zn anode. PMID:26098753

  4. Investigation of a self-sustained volume discharge in c-C4F8

    NASA Astrophysics Data System (ADS)

    Belevtsev, A. A.; Firsov, K. N.; Kazantsev, S. Yu; Kononov, I. G.; Podlesnykh, S. V.

    2015-11-01

    This paper reports the first experimental study of a self-sustained volume discharge (SSVD) in c-C4F8. The discharge voltage and current oscillograms are taken over a wide range of gas pressures. For the first time an SSVD in c-C4F8 preheated by CO2-laser radiation has been investigated. Some special features and temperature-dependent characteristics of this discharge are revealed. There is discussion on the peculiarities of an SSVD in a preirradiated c-C4F8. To refine the static limiting field in c-C4F8 the static dielectric strength of c-C4F8 is measured on changing the gas pressure by nearly two orders of magnitude.

  5. Intramolecular Hydrogen Bonding in Methyl Lactate.

    PubMed

    Schrder, Sidsel D; Wallberg, Jens H; Kroll, Jay A; Maroun, Zeina; Vaida, Veronica; Kjaergaard, Henrik G

    2015-09-17

    The intramolecular hydrogen bonding in methyl lactate was studied with Fourier transform infrared (FTIR) spectroscopy, intracavity laser photoacoustic spectroscopy, and cavity ring-down spectroscopy. Vapor phase spectra were recorded in the ?vOH = 1-4 OH-stretching regions, and the observed OH-stretching transitions were compared with theoretical results. Transition frequencies and oscillator strengths were obtained using a one-dimensional anharmonic oscillator local mode model with potential energy and dipole moment surfaces calculated at the CCSD(T)-F12a/VDZ-F12 level. The three most abundant conformers of methyl lactate all appear to possess an intramolecular hydrogen bond, with the hydroxyl group forming a hydrogen bond with either the carbonyl or ester oxygen. The intramolecular hydrogen bonds were investigated theoretically by analyses based on electron density topology, natural bond orbital analysis, and visualization of the electrostatic potential energy. PMID:26296230

  6. Prospective bonding applications

    NASA Astrophysics Data System (ADS)

    Ancenay, H.; Benazet, D.

    1981-07-01

    Adhesive bonding in industry and in the laboratory is surveyed and prospects for its wider utilization are assessed. The economic impact of bonding technology on industry is discussed. Research is reviewed, centering on the development of nondestructive testing and inspection techniques. Traditional (wood) as well as new materials susceptible to bonding are considered. Applications in construction and civil engineering, in aeronautics, and in the automobile industry are covered. The use of glues in mechanical constructions, in assembling cylindrical parts, and in metal-metal bonding are examined. Hybrid assembling and bonding of composite materials are included.

  7. Bonding thermoplastic polymers

    DOEpatents

    Wallow, Thomas I. (Fremont, CA); Hunter, Marion C. (Livermore, CA); Krafcik, Karen Lee (Livermore, CA); Morales, Alfredo M. (Livermore, CA); Simmons, Blake A. (San Francisco, CA); Domeier, Linda A. (Danville, CA)

    2008-06-24

    We demonstrate a new method for joining patterned thermoplastic parts into layered structures. The method takes advantage of case-II permeant diffusion to generate dimensionally controlled, activated bonding layers at the surfaces being joined. It is capable of producing bonds characterized by cohesive failure while preserving the fidelity of patterned features in the bonding surfaces. This approach is uniquely suited to production of microfluidic multilayer structures, as it allows the bond-forming interface between plastic parts to be precisely manipulated at micrometer length scales. The bond enhancing procedure is easily integrated in standard process flows and requires no specialized equipment.

  8. Hydrogen multicentre bonds

    NASA Astrophysics Data System (ADS)

    Janotti, Anderson; van de Walle, Chris G.

    2007-01-01

    The concept of a chemical bond stands out as a major development in the process of understanding how atoms are held together in molecules and solids. Lewis' classical picture of chemical bonds as shared-electron pairs evolved to the quantum-mechanical valence-bond and molecular-orbital theories, and the classification of molecules and solids in terms of their bonding type: covalent, ionic, van der Waals and metallic. Along with the more complex hydrogen bonds and three-centre bonds, they form a paradigm within which the structure of almost all molecules and solids can be understood. Here, we present evidence for hydrogen multicentre bonds-a generalization of three-centre bonds-in which a hydrogen atom equally bonds to four or more other atoms. When substituting for oxygen in metal oxides, hydrogen bonds equally to all the surrounding metal atoms, becoming fourfold coordinated in ZnO, and sixfold coordinated in MgO. These multicentre bonds are remarkably strong despite their large hydrogen-metal distances. The calculated local vibration mode frequency in MgO agrees with infrared spectroscopy measurements. Multicoordinated hydrogen also explains the dependence of electrical conductivity on oxygen partial pressure, resolving a long-standing controversy on the role of point defects in unintentional n-type conductivity of ZnO (refs 8-10).

  9. AlkyneAldehyde Reductive CC Coupling through Ruthenium-Catalyzed Transfer Hydrogenation: Direct Regio- and Stereoselective Carbonyl Vinylation to Form Trisubstituted Allylic Alcohols in the Absence of Premetallated Reagents

    PubMed Central

    Leung, Joyce C.; Patman, Ryan L.; Sam, Brannon

    2011-01-01

    Nonsymmetric 1,2-disubstituted alkynes engage in reductive coupling to a variety of aldehydes under the conditions of ruthenium-catalyzed transfer hydrogenation by employing formic acid as the terminal reductant and delivering the products of carbonyl vinylation with good to excellent levels of regioselectivity and with complete control of olefin stereochemistry. As revealed in an assessment of the ruthenium counterion, iodide plays an essential role in directing the regioselectivity of CC bond formation. Isotopic labeling studies corroborate reversible catalytic propargyl CH oxidative addition in advance of the CC coupling, and demonstrate that the CC coupling products do not experience reversible dehydrogenation by way of enone intermediates. This transfer hydrogenation protocol enables carbonyl vinylation in the absence of stoichiometric metallic reagents. PMID:21953608

  10. Proton stopping in C+C, d+C, C+Ta and d+Ta collisions at 4.2A GeV/c

    E-print Network

    Lj. Simic; M. Kornicer

    1998-07-31

    The shape of proton rapidity distributions is analysed in terms of their Gaussian components, and the average rapidity loss is determined in order to estimate the amount of stopping in C+C, d+C, C+Ta and d+Ta collisions at 4.2A GeV/c. Three Gaussians correspond to the nuclear transparency and describe well all peripheral and also C+C central collisions. Two-component shape is obtained in case of d+C and C+Ta central collisions. Finally one Gaussian, found in d+Ta central collisions, corresponds to the full stopping. The calculated values of the average rapidity loss support the qualitative relationship between the number of Gaussian components and the corresponding stopping power. It is also observed, in central collisions, that the average rapidity loss increases with the ratio of the number of target and the number of projectile participants.

  11. 25 CFR 225.30 - Bonds.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS OIL AND GAS, GEOTHERMAL, AND SOLID MINERALS AGREEMENTS...a $75,000 bond for all geothermal, mining, or oil and...nationwide coverage to cover all geothermal or oil and gas...

  12. 25 CFR 225.30 - Bonds.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS OIL AND GAS, GEOTHERMAL, AND SOLID MINERALS AGREEMENTS...a $75,000 bond for all geothermal, mining, or oil and...nationwide coverage to cover all geothermal or oil and gas...

  13. 25 CFR 225.30 - Bonds.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS OIL AND GAS, GEOTHERMAL, AND SOLID MINERALS AGREEMENTS...a $75,000 bond for all geothermal, mining, or oil and...nationwide coverage to cover all geothermal or oil and gas...

  14. 25 CFR 225.30 - Bonds.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS OIL AND GAS, GEOTHERMAL, AND SOLID MINERALS AGREEMENTS...a $75,000 bond for all geothermal, mining, or oil and...nationwide coverage to cover all geothermal or oil and gas...

  15. 25 CFR 227.8 - Bonds.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...227.8 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF CERTAIN LANDS IN WIND RIVER INDIAN RESERVATION, WYOMING, FOR OIL AND GAS MINING How to Acquire Leases 227.8 Bonds. The provisions...

  16. 25 CFR 227.8 - Bonds.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...227.8 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF CERTAIN LANDS IN WIND RIVER INDIAN RESERVATION, WYOMING, FOR OIL AND GAS MINING How to Acquire Leases 227.8 Bonds. The provisions...

  17. 25 CFR 227.8 - Bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...227.8 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR ENERGY AND MINERALS LEASING OF CERTAIN LANDS IN WIND RIVER INDIAN RESERVATION, WYOMING, FOR OIL AND GAS MINING How to Acquire Leases 227.8 Bonds. The provisions...

  18. Unimolecular dissociation of the propargyl radical intermediate of the CH+C2H2 and C+C2H3 reactions

    E-print Network

    Butler, Laurie J.

    Unimolecular dissociation of the propargyl radical intermediate of the CH+C2H2 and C+C2H3 reactions examines the unimolecular dissociation of propargyl HCCCH2 radicals over a range of internal energies/mol as the lowest barrier to dissociation of the radical. This barrier is significantly lower than predictions

  19. Competition of C(sp)-XO halogen bonding and lone pair? interactions: cryospectroscopic study of the complexes of C?F?X (X = F, Cl, Br, and I) and dimethyl ether.

    PubMed

    Geboes, Yannick; Nagels, Nick; Pinter, Balazs; De Proft, Frank; Herrebout, Wouter A

    2015-03-19

    Inspection of the electrostatic potential of C2F3X (X = F, Cl, Br, and I) revealed a second electropositive region in the immediate vicinity of the C?C double bond apart from the ? hole of chlorine, bromine, and iodine, leading to C(sp(2))-XY halogen bonding, through which complexes stabilized by so-called lone pair? interactions can be formed. Consequently, the experimental studies for the complexes of dimethyl ether with C2F3X (X = F, Cl, Br, and I) not only allowed one to experimentally characterize and rationalize the effects of hybridization on halogen bonding but, for the first time, also allowed the competition of C-XY halogen bonding and lone pair? interactions to be studied at thermodynamic equilibrium. Analysis of the infrared and Raman spectra reveals that in the cryosolutions of dimethyl ether and C2F3I, solely the halogen-bonded complex is present, whereas C2F3Br and C2F3Cl give rise to a lone pair? bonded complex as well as a halogen-bonded complex. Mixtures of dimethyl ether with C2F4 solely yield a lone pair? bonded complex. The experimentally derived complexation enthalpies for the halogen bonded complexes are found to be -14.2(5) kJ mol(-1) for C2F3IDME and -9.3(5) kJ mol(-1) for C2F3BrDME. For the complexes of C2F3Cl with dimethyl ether, no experimental complexation enthalpy could be obtained, whereas the C2F4DME complex has a complexation enthalpy of -5.5(3) kJ mol(-1). The observed trends have been rationalized with the aid of an interaction energy decomposition analysis (EDA) coupled to a Natural Orbital for Chemical Valence (NOCV) analysis and also using the noncovalent interaction index method. PMID:25390877

  20. Phosphodiester bond rupture in 5? and 3? cytosine monophosphate in aqueous environment and the effect of low-energy electron attachment: A Car Parrinello QM/MM molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Schyman, Patric; Laaksonen, Aatto; Hugosson, Hkan W.

    2008-09-01

    In this study we have explored the effect of low-energy electrons (LEEs) when rupturing the C3'-O3' and C5'-O5' bonds in 3' and 5' cytosine monophosphate in an aqueous environment. This has been done using a hybrid quantum mechanics/classical mechanics (QM/MM) setup within the framework of Car-Parrinello molecular dynamics (CPMD). Our results are in agreement with experimental findings and indicate that LEEs do not drastically lower the energy barrier for breaking the 3' or 5' phosphodiester bonds for single cytosine nucleotides in aqueous environment.

  1. Ultrasonic emission method enables testing of adhesive bonds

    NASA Technical Reports Server (NTRS)

    Frank, L.; Schmitz, G.

    1966-01-01

    Detection of acoustic energy emitted by adhesive bonds subjected to tensile stresses at frequencies above sixteen kilocycles per second is used as a method for determining bond strength. This method is used in measuring adhesive bond strengths on metal honeycomb core panels.

  2. Catalytic hydrofunctionalization of alkynes through P-H bond addition: the unique role of orientation and properties of the phosphorus group in the insertion step.

    PubMed

    Ananikov, Valentine P; Makarov, Anton V; Beletskaya, Irina P

    2011-11-01

    The puzzling question of alkyne insertion into Pd-P and Pd-H bonds leading to the formation of new Pd-C, C-P, and C-H bonds was explored by theoretical calculations at the CCSD(T) and B3LYP levels of theory. The key factors responsible for selectivity of catalytic hydrofunctionalization of alkynes were resolved and studied in details for the models of hydrophosphorylation, hydrophosphinylation, and hydrophospination reactions. In contrast with the generally accepted mechanistic picture, the calculations have shown that several pathways are possible depending on the nature and geometrical arrangement of the phosphorus group. It was found that the product of alkyne insertion into the metal-hydrogen bond should be easily formed under kinetic-control conditions, while the product of alkyne insertion into the metal-phosphorus bond may be formed in certain cases under thermodynamic control. For the first time, the calculations have revealed the role of the oxygen atom in the reactivity of P=P(O)R(2) groups and the role of the interactions involving the lone pair of the P=PR(2) group in the reagent. The fundamental properties of the Pd-P, C-P, and P-H bonds were reported, and the larger bond strength upon increasing the number of oxygen atoms bound to phosphorus (P=PR(2), P(O)R(2), and P(O)(OR)(2)) have been shown. The relationship between bond energy, acidity, and reactivity of the studied phosphorus compounds has been determined. PMID:21971879

  3. Characteristics of hydrogen bond revealed from water clusters

    NASA Astrophysics Data System (ADS)

    Song, Yan; Chen, Hongshan; Zhang, Cairong; Zhang, Yan; Yin, Yuehong

    2014-09-01

    The hydrogen bond network is responsible for the exceptional physical and chemical properties of water, however, the description of hydrogen bond remains a challenge for the studies of condensed water. The investigation of structural and binding properties of water clusters provides a key for understanding the H-bonds in bulk water. In this paper, a new set of geometric parameters are defined to describe the extent of the overlap between the bonding orbital of the donor OH and the nonbonding orbital of the lone-pair of the acceptor molecule. This orbital overlap plays a dominant role for the strength of H-bonds. The dependences of the binding energy of the water dimer on these parameters are studied. The results show that these parameters properly describe the H-bond strength. The ring, book, cage and prism isomers of water hexamer form 6, 7, 8 and 9 H-bonds, and the strength of the bonding in these isomers changes markedly. The internally-solvated and the all-surface structures of (H2O) n for n = 17, 19 and 21 are nearly isoenergetic. The internally-solvated isomers form fewer but stronger H-bonds. The hydrogen bonding in the above clusters are investigated in detail. The geometric parameters can well describe the characters of the H-bonds, and they correlate well with the H-bond strength. For the structures forming stronger H-bonds, the H-bond lengths are shorter, the angle parameters are closer to the optimum values, and their rms deviations are smaller. The H-bonds emanating from DDAA and DDA molecules as H-donor are relatively weak. The vibrational spectra of (H2O) n ( n = 17, 19 and 21) are studied as well. The stretching vibration of the intramolecular OH bond is sensitive to its bonding environment. The H-bond strength judged from the geometric parameters is in good agreement with the bonding strength judged from the stretching frequencies.

  4. Coherent Behavior and the Bound State of Water and K+ Imply Another Model of Bioenergetics: Negative Entropy Instead of High-energy Bonds

    PubMed Central

    Jaeken, Laurent; Vasilievich Matveev, Vladimir

    2012-01-01

    Observations of coherent cellular behavior cannot be integrated into widely accepted membrane (pump) theory (MT) and its steady state energetics because of the thermal noise of assumed ordinary cell water and freely soluble cytoplasmic K+. However, Ling disproved MT and proposed an alternative based on coherence, showing that rest (R) and action (A) are two different phases of protoplasm with different energy levels. The R-state is a coherent metastable low-entropy state as water and K+ are bound to unfolded proteins. The A-state is the higher-entropy state because water and K+ are free. The R-to-A phase transition is regarded as a mechanism to release energy for biological work, replacing the classical concept of high-energy bonds. Subsequent inactivation during the endergonic A-to-R phase transition needs an input of metabolic energy to restore the low entropy R-state. Matveevs native aggregation hypothesis allows to integrate the energetic details of globular proteins into this view. PMID:23264833

  5. Probing molecular interaction in ionic liquids by low frequency spectroscopy: Coulomb energy, hydrogen bonding and dispersion forces.

    PubMed

    Fumino, Koichi; Reimann, Sebastian; Ludwig, Ralf

    2014-10-28

    Ionic liquids are defined as salts composed solely of ions with melting points below 100 C. These remarkable liquids have unique and fascinating properties and offer new opportunities for science and technology. New combinations of ions provide changing physical properties and thus novel potential applications for this class of liquid materials. To a large extent, the structure and properties of ionic liquids are determined by the intermolecular interaction between anions and cations. In this perspective we show that far infrared and terahertz spectroscopy are suitable methods for studying the cation-anion interaction in these Coulomb fluids. The interpretation of the measured low frequency spectra is supported by density functional theory calculations and molecular dynamics simulations. We present results for selected aprotic and protic ionic liquids and their mixtures with molecular solvents. In particular, we focus on the strength and type of intermolecular interaction and how both parameters are influenced by the character of the ions and their combinations. We show that the total interaction between cations and anions is a result of a subtle balance between Coulomb forces, hydrogen bonds and dispersion forces. For protic ionic liquids we could measure distinct vibrational modes in the low frequency spectra indicating clearly the cation-anion interaction characterized by linear and medium to strong hydrogen bonds. Using isotopic substitution we have been able to dissect frequency shifts related to pure interaction strength between cations and anions and to different reduced masses only. In this context we also show how these different types of interaction may influence the physical properties of ionic liquids such as the melting point, viscosity or enthalpy of vaporization. Furthermore we demonstrate that low frequency spectroscopy can also be used for studying ion speciation. Low vibrational features can be assigned to contact ion pairs and solvent separated ion pairs. In conclusion we showed how detailed knowledge of the low frequency spectra can be used to understand the change in interaction strength and structure by variation of temperature, solvent polarity and solvent concentration in ionic liquids and their mixtures with molecular solvents. In principle the used combination of methods is suitable for studying intermolecular interaction in pure molecular liquids and their solutions including additive materials such as nanoparticles. PMID:24898478

  6. S-OO bond dissociation energies and enthalpies of formation of the thiomethyl peroxyl radicals CH{sub 3}S(O){sub n}OO (n=0,1,2)

    SciTech Connect

    Salta, Zoi; Kosmas, Agnie Mylona; Lesar, Antonija

    2014-10-06

    Optimized geometries, S-OO bond dissociation energies and enthalpies of formation for a series of thiomethyl peroxyl radicals are investigated using high level ab initio and density functional theory methods. The results show that the S-OO bond dissociation energy is largest in the methylsulfonyl peroxyl radical, CH{sub 3}S(O){sub 2}OO, which contains two sulfonic type oxygen atoms followed by the methylthiyl peroxyl radical, CH{sub 3}SOO. The methylsulfinyl peroxyl radical, CH{sub 3}S(O)OO, which contains only one sulfonic type oxygen shows the least stability with regard to dissociation to CH{sub 3}S(O)+O{sub 2}. This stabilization trend is nicely reflected in the variations of the S-OO bond distance which is found to be shortest in CH{sub 3}S(O){sub 2}OO and longest in CH{sub 3}S(O)OO.

  7. Bonded semiconductor substrate

    DOEpatents

    Atwater, Jr.; Harry A. (South Pasadena, CA), Zahler; James M. (Pasadena, CA)

    2010-07-13

    Ge/Si and other nonsilicon film heterostructures are formed by hydrogen-induced exfoliation of the Ge film which is wafer bonded to a cheaper substrate, such as Si. A thin, single-crystal layer of Ge is transferred to Si substrate. The bond at the interface of the Ge/Si heterostructures is covalent to ensure good thermal contact, mechanical strength, and to enable the formation of an ohmic contact between the Si substrate and Ge layers. To accomplish this type of bond, hydrophobic wafer bonding is used, because as the invention demonstrates the hydrogen-surface-terminating species that facilitate van der Waals bonding evolves at temperatures above 600.degree. C. into covalent bonding in hydrophobically bound Ge/Si layer transferred systems.

  8. Evaluation of shear bond strength of porcelain bonded to laser welded titanium surface and determination of mode of bond failure.

    PubMed

    Patil, Narendra P; Dandekar, Minal; Nadiger, Ramesh K; Guttal, Satyabodh S

    2010-09-01

    The aim of this study was to evaluate the shear bond strength of porcelain to laser welded titanium surface and to determine the mode of bond failure through scanning electron microscopy (SEM) and energy dispersive spectrophotometry (EDS). Forty five cast rectangular titanium specimens with the dimension of 10 mm x 8 mm x 1 mm were tested. Thirty specimens had a perforation of 2 mm diameter in the centre. These were randomly divided into Group A and B. The perforations in the Group B specimens were repaired by laser welding using Cp Grade II titanium wire. The remaining 15 specimens were taken as control group. All the test specimens were layered with low fusing porcelain and tested for shear bond strength. The debonded specimens were subjected to SEM and EDS. Data were analysed with 1-way analysis of variance and Student's t-test for comparison among the different groups. One-way analysis of variance (ANOVA) showed no statistically significant difference in shear bond strength values at a 5% level of confidence. The mean shear bond strength values for control group, Group A and B was 8.4 +/- 0.5 Mpa, 8.1 +/- 0.4 Mpa and 8.3 +/- 0.3 Mpa respectively. SEM/EDS analysis of the specimens showed mixed and cohesive type of bond failure. Within the limitations of the study laser welding did not have any effect on the shear bond strength of porcelain bonded to titanium. PMID:21077419

  9. Chemical bonding technology

    NASA Technical Reports Server (NTRS)

    Plueddemann, E.

    1986-01-01

    Primers employed in bonding together the various material interfaces in a photovoltaic module are being developed. The approach develops interfacial adhesion by generating actual chemical bonds between the various materials bonded together. The current status of the program is described along with the progress toward developing two general purpose primers for ethylene vinyl acetate (EVA), one for glass and metals, and another for plastic films.

  10. General Education Coursework: Credits General Education Coursework: Credits ENGL 110C (C or better) 3 ENGL 211C, 221C or 231C ( C or better) 3

    E-print Network

    General Education Coursework: Credits General Education Coursework: Credits ENGL 110C (C or better: Credits General Education Coursework: Credits Information Literacy and Research 3 Human Creativity 3 BIOL SEMESTER (17 credits) SPRING SEMESTER (18 Major Coursework: Major Coursework: Major Coursework: Credits

  11. Pd-Catalyzed CdC Double-Bond Formation by Coupling of

    E-print Network

    Wang, Jianbo

    reagents, see: (a) Crawforth, C. M.; Burling, S.; Fairlamb, I. J. S.; Taylor, R. J. K.; Whitwood, A. C, C. M.; Fairlamb, I. J. S.; Kapdi, A. R.; Serrano, J. L.; Taylor, R. J. K.; Sanchez, G. AdV. SynthPd-Catalyzed CdC Double-Bond Formation by Coupling of N-Tosylhydrazones with Benzyl Halides Qing

  12. (N-heterocyclic-carbene)Copper(I)-catalyzed carbon-carbon bond formation using carbon dioxide

    E-print Network

    Sirokman, Gergely

    2007-01-01

    This thesis presents work towards the development of a new catalytic C-C bond forming reaction. Alkynes and olefins insert into [(IPr)CuH]2 (IPr = N,N-bis-(2,6-diisopropylphenyl)-1,3-imidazol-2-ylidene) to give copper vinyl ...

  13. Geometrical effects of phospholipid olefinic bonds on the structure and dynamics of membranes: A molecular dynamics study.

    PubMed

    Tsai, Hui-Hsu Gavin; Lee, Jian-Bin; Li, Hung-Sheng; Hou, Tsai-Yi; Chu, Wen-Yuan; Shen, Po-Chuan; Chen, Ying-Yu; Tan, Chun-Jui; Hu, Jia-Cheng; Chiu, Chih-Chiang

    2015-05-01

    The trans isomers of fatty acids are found in human adipose tissue. These isomers have been linked with deleterious health effects (e.g., coronary artery disease). In this study, we performed molecular dynamics simulations to investigate the structures and dynamic properties of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) and 1-palmitoyl-2-elaidoyl sn-glycero-3-phosphatidylcholine (PEPC) lipid bilayers. The geometry of the olefinic bond and membrane packing effects significantly influenced the conformations and dynamics of the two C-C single bonds adjacent to the olefinic bond. For the PEPC lipid, the two C-C single bonds adjacent to the olefinic bond adopted mainly nonplanar skew-trans and planar cis-trans motifs; although the cis conformation featured relatively strong steric repulsion, it was stabilized through membrane packing because its planar structure is more suitable for membrane packing. Moreover, membrane packing effects stabilized the planar transition state for conformational conversion to a greater extent than they did with the nonplanar transition state, thereby affecting the dynamics of conformational conversion. The rotational motions of the first neighboring C-C single bonds were much faster than those of typical saturated C-C single bonds; in contrast, the rotational motions of the second neighboring C-C single bonds were significantly slower than those of typical saturated torsion angles. The packing of PEPC lipids is superior to that of POPC lipids, leading to a smaller area per lipid, a higher order parameter and a smaller diffusion coefficient. The distinct properties of POPC and PEPC lipids result in PEPC lipids forming microdomains within a POPC matrix. PMID:25732027

  14. Brazing of C/C composites and Ni-based alloy using interlayer

    NASA Astrophysics Data System (ADS)

    Ikeshoji, Toshi-Taka; Tokunaga, Tatsuya; Suzumura, Akio; Yamazaki, Takahisa

    2014-08-01

    The brazing of C/C composites and Inconel-600 Ni-based heat resistant alloy was conducted using Fe-Ni-Cr-P-Si brazing filler alloy with inserting various thickness of Nb foil as stress relief interlayer. SEM observation of cross section of brazing interface revealed that Nb foil was resolved into the brazing filler layer on C/C composites side. Nb diffused to the surface of C/C composites and acted as the active metal element to enhance the wettability of molten metal on graphite matrix of C/C composites during the brazing process. The variation in shear strength values of the brazed joint with Nb layer thickness suggested that the Nb layer should be remained at least 100 ?m.

  15. Observation of the decay $?(3686)$ $\\rightarrow$ $?\\bar?^{\\pm}?^{\\mp}+c.c.$

    E-print Network

    BESIII collaboration; M. Ablikim; M. N. Achasov; X. C. Ai; O. Albayrak; D. J. Ambrose; F. F. An; Q. An; J. Z. Bai; R. Baldini Ferroli A; Y. Ban; J. V. Bennett; M. Bertani A; J. M. Bian; E. Boger; O. Bondarenko; I. Boyko; S. Braun; R. A. Briere; H. Cai; X. Cai; O. Cakir A; A. Calcaterra A; G. F. Cao; S. A. Cetin B; J. F. Chang; G. Chelkov; G. Chen; H. S. Chen; J. C. Chen; M. L. Chen; S. J. Chen; X. Chen; X. R. Chen; Y. B. Chen; H. P. Cheng; X. K. Chu; Y. P. Chu; D. Cronin-Hennessy; H. L. Dai; J. P. Dai; D. Dedovich; Z. Y. Deng; A. Denig; I. Denysenko; M. Destefanis; W. M. Ding; Y. Ding; C. Dong; J. Dong; L. Y. Dong; M. Y. Dong; S. X. Du; J. Fang; S. S. Fang; Y. Fang; L. Fava; C. Q. Feng; C. D. Fu; J. L. Fu; O. Fuks; Q. Gao; Y. Gao; C. Geng; K. Goetzen; W. X. Gong; W. Gradl; M. Greco; M. H. Gu; Y. T. Gu; Y. H. Guan; A. Q. Guo; L. B. Guo; T. Guo; Y. P. Guo; Y. P. Guo; Y. L. Han; F. A. Harris; K. L. He; M. He; Z. Y. He; T. Held; Y. K. Heng; Z. L. Hou; C. Hu; H. M. Hu; J. F. Hu; T. Hu; G. M. Huang; G. S. Huang; J. S. Huang; L. Huang; X. T. Huang; T. Hussain; C. S. Ji; Q. Ji; Q. P. Ji; X. B. Ji; X. L. Ji; L. L. Jiang; X. S. Jiang; J. B. Jiao; Z. Jiao; D. P. Jin; S. Jin; F. F. Jing; T. Johansson; N. Kalantar-Nayestanaki; X. L. Kang; M. Kavatsyuk; B. Kloss; B. Kopf; M. Kornicer; W. Kuehn; A. Kupsc; W. Lai; J. S. Lange; M. Lara; P. Larin; M. Leyhe; C. H. Li; Cheng Li; Cui Li; D. Li; D. M. Li; F. Li; G. Li; H. B. Li; J. C. Li; K. Li; K. Li; Lei Li; P. R. Li; Q. J. Li; T. Li; W. D. Li; W. G. Li; X. L. Li; X. N. Li; X. Q. Li; X. R. Li; Z. B. Li; H. Liang; Y. F. Liang; Y. T. Liang; G. R. Liao; D. X. Lin; B. J. Liu; C. L. Liu; C. X. Liu; F. H. Liu; Fang Liu; Feng Liu; H. B. Liu; H. H. Liu; H. M. Liu; J. Liu; J. P. Liu; K. Liu; K. Y. Liu; P. L. Liu; Q. Liu; S. B. Liu; X. Liu; Y. B. Liu; Z. A. Liu; Zhiqiang Liu; Zhiqing Liu; H. Loehner; X. C. Lou; G. R. Lu; H. J. Lu; H. L. Lu; J. G. Lu; X. R. Lu; Y. Lu; Y. P. Lu; C. L. Luo; M. X. Luo; T. Luo; X. L. Luo; M. Lv; F. C. Ma; H. L. Ma; Q. M. Ma; S. Ma; T. Ma; X. Y. Ma; F. E. Maas; M. Maggiora; Q. A. Malik; Y. J. Mao; Z. P. Mao; J. G. Messchendorp; J. Min; T. J. Min; R. E. Mitchell; X. H. Mo; H. Moeini; C. Morales Morales; K. Moriya; N. Yu. Muchnoi; Y. Nefedov; I. B. Nikolaev; Z. Ning; S. Nisar; X. Y. Niu; S. L. Olsen; Q. Ouyang; S. Pacetti B; M. Pelizaeus; H. P. Peng; K. Peters; J. L. Ping; R. G. Ping; R. Poling; E. Prencipe; M. Qi; S. Qian; C. F. Qiao; L. Q. Qin; X. S. Qin; Y. Qin; Z. H. Qin; J. F. Qiu; K. H. Rashid; C. F. Redmer; M. Ripka; G. Rong; X. D. Ruan; A. Sarantsev; K. Schinning; S. Schumann; W. Shan; M. Shao; C. P. Shen; X. Y. Shen; H. Y. Sheng; M. R. Shepherd; W. M. Song; X. Y. Song; S. Spataro; B. Spruck; G. X. Sun; J. F. Sun; S. S. Sun; Y. J. Sun; Y. Z. Sun; Z. J. Sun; Z. T. Sun; C. J. Tang; X. Tang; I. Tapan; E. H. Thorndike; D. Toth; M. Ullrich; I. Uman B; G. S. Varner; B. Wang; D. Wang; D. Y. Wang; K. Wang; L. L. Wang; L. S. Wang; M. Wang; P. Wang; P. L. Wang; Q. J. Wang; S. G. Wang; W. Wang; X. F. Wang; Y. D. Wang A; Y. F. Wang; Y. Q. Wang; Z. Wang; Z. G. Wang; Z. H. Wang; Z. Y. Wang; D. H. Wei; J. B. Wei; P. Weidenkaff; S. P. Wen; M. Werner; U. Wiedner; M. Wolke; G. G. Wu; L. H. Wu; N. Wu; W. Wu; Z. Wu; L. G. Xia; Y. Xia; D. Xiao; Z. J. Xiao; Y. G. Xie; Q. L. Xiu; G. F. Xu; L. Xu; Q. J. Xu; Q. N. Xu; X. P. Xu; Z. Xue; L. Yan; W. B. Yan; W. C. Yan; Y. H. Yan; H. X. Yang; Y. Yang; Y. X. Yang; H. Ye; M. Ye; M. H. Ye; B. X. Yu; C. X. Yu; H. W. Yu; J. S. Yu; S. P. Yu; C. Z. Yuan; W. L. Yuan; Y. Yuan; A. A. Zafar; A. Zallo A; S. L. Zang; Y. Zeng; B. X. Zhang; B. Y. Zhang; C. Zhang; C. B. Zhang; C. C. Zhang; D. H. Zhang; H. H. Zhang; H. Y. Zhang; J. J. Zhang; J. L. Zhang; J. Q. Zhang; J. W. Zhang; J. Y. Zhang; J. Z. Zhang; S. H. Zhang; X. J. Zhang; X. Y. Zhang; Y. Zhang; Y. H. Zhang; Z. H. Zhang; Z. P. Zhang; Z. Y. Zhang; G. Zhao; J. W. Zhao; Lei Zhao; Ling Zhao; M. G. Zhao; Q. Zhao; Q. W. Zhao; S. J. Zhao; T. C. Zhao; X. H. Zhao; Y. B. Zhao; Z. G. Zhao; A. Zhemchugov; B. Zheng; J. P. Zheng; Y. H. Zheng; B. Zhong; L. Zhou; Li Zhou; X. Zhou; X. K. Zhou; X. R. Zhou; X. Y. Zhou; K. Zhu; K. J. Zhu; X. L. Zhu; Y. C. Zhu; Y. S. Zhu; Z. A. Zhu; J. Zhuang; B. S. Zou; J. H. Zou

    2013-10-22

    Using a sample of $1.06\\times10^{8}$ $\\psi(3686)$ events collected with the BESIII detector, we present the first observation of the decays of $\\psi(3686)$ $\\rightarrow$ $\\Lambda\\bar\\Sigma^{+}\\pi^{-}+c.c.$ and $\\psi(3686)$ $\\rightarrow$ $\\Lambda\\bar\\Sigma^{-}\\pi^{+}+c.c.$. The branching fractions are measured to be $\\mathcal{B}(\\psi(3686) \\rightarrow \\Lambda\\bar\\Sigma^{+}\\pi^{-} + c.c.)=(1.40\\pm 0.03 \\pm 0.13)\\times10^{-4}$ and $\\mathcal{B}(\\psi(3686) \\rightarrow \\Lambda\\bar\\Sigma^{-}\\pi^{+}+c.c.)=(1.54\\pm 0.04 \\pm 0.13)\\times10^{-4}$, where the first errors are statistical and the second ones systematic.

  16. Search for the weak decays J /? ?Ds(*)-e+?e+c .c .

    NASA Astrophysics Data System (ADS)

    Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; An, F. F.; An, Q.; Bai, J. Z.; Ferroli, R. Baldini; Ban, Y.; Bennett, D. W.; Bennett, J. V.; Bertani, M.; Bettoni, D.; Bian, J. M.; Bianchi, F.; Boger, E.; Bondarenko, O.; Boyko, I.; Briere, R. A.; Cai, H.; Cai, X.; Cakir, O.; Calcaterra, A.; Cao, G. F.; Cetin, S. A.; Chang, J. F.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, H. Y.; Chen, J. C.; Chen, M. L.; Chen, S. J.; Chen, X.; Chen, X. R.; Chen, Y. B.; Cheng, H. P.; Chu, X. K.; Chu, Y. P.; Cibinetto, G.; Cronin-Hennessy, D.; Dai, H. L.; Dai, J. P.; Dedovich, D.; Deng, Z. Y.; Denig, A.; Denysenko, I.; Destefanis, M.; de Mori, F.; Ding, Y.; Dong, C.; Dong, J.; Dong, L. Y.; Dong, M. Y.; Du, S. X.; Duan, P. F.; Fan, J. Z.; Fang, J.; Fang, S. S.; Fang, X.; Fang, Y.; Fava, L.; Feldbauer, F.; Felici, G.; Feng, C. Q.; Fioravanti, E.; Fu, C. D.; Gao, Q.; Gao, Y.; Garzia, I.; Goetzen, K.; Gong, W. X.; Gradl, W.; Greco, M.; Gu, M. H.; Gu, Y. T.; Guan, Y. H.; Guo, A. Q.; Guo, L. B.; Guo, T.; Guo, Y.; Guo, Y. P.; Haddadi, Z.; Hafner, A.; Han, S.; Han, Y. L.; Harris, F. A.; He, K. L.; He, Z. Y.; Held, T.; Heng, Y. K.; Hou, Z. L.; Hu, C.; Hu, H. M.; Hu, J. F.; Hu, T.; Hu, Y.; Huang, G. M.; Huang, G. S.; Huang, H. P.; Huang, J. S.; Huang, X. T.; Huang, Y.; Hussain, T.; Ji, Q.; Ji, Q. P.; Ji, X. B.; Ji, X. L.; Jiang, L. L.; Jiang, L. W.; Jiang, X. S.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Johansson, T.; Julin, A.; Kalantar-Nayestanaki, N.; Kang, X. L.; Kang, X. S.; Kavatsyuk, M.; Ke, B. C.; Kliemt, R.; Kloss, B.; Kolcu, O. B.; Kopf, B.; Kornicer, M.; Kuehn, W.; Kupsc, A.; Lai, W.; Lange, J. S.; Lara, M.; Larin, P.; Li, C. H.; Li, Cheng; Li, D. M.; Li, F.; Li, G.; Li, H. B.; Li, J. C.; Li, Jin; Li, K.; Li, K.; Li, P. R.; Li, T.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. M.; Li, X. N.; Li, X. Q.; Li, Z. B.; Liang, H.; Liang, Y. F.; Liang, Y. T.; Liao, G. R.; Lin, D. X.; Liu, B. J.; Liu, C. L.; Liu, C. X.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, H. B.; Liu, H. H.; Liu, H. H.; Liu, H. M.; Liu, J.; Liu, J. P.; Liu, J. Y.; Liu, K.; Liu, K. Y.; Liu, L. D.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, X. X.; Liu, Y. B.; Liu, Z. A.; Liu, Zhiqiang; Liu, Zhiqing; Loehner, H.; Lou, X. C.; Lu, H. J.; Lu, J. G.; Lu, R. Q.; Lu, Y.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, T.; Luo, X. L.; Lv, M.; Lyu, X. R.; Ma, F. C.; Ma, H. L.; Ma, L. L.; Ma, Q. M.; Ma, S.; Ma, T.; Ma, X. N.; Ma, X. Y.; Maas, F. E.; Maggiora, M.; Malik, Q. A.; Mao, Y. J.; Mao, Z. P.; Marcello, S.; Messchendorp, J. G.; Min, J.; Min, T. J.; Mitchell, R. E.; Mo, X. H.; Mo, Y. J.; Moeini, H.; Morales, C. Morales; Moriya, K.; Muchnoi, N. Yu.; Muramatsu, H.; Nefedov, Y.; Nerling, F.; Nikolaev, I. B.; Ning, Z.; Nisar, S.; Niu, S. L.; Niu, X. Y.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Patteri, P.; Pelizaeus, M.; Peng, H. P.; Peters, K.; Ping, J. L.; Ping, R. G.; Poling, R.; Pu, Y. N.; Qi, M.; Qian, S.; Qiao, C. F.; Qin, L. Q.; Qin, N.; Qin, X. S.; Qin, Y.; Qin, Z. H.; Qiu, J. F.; Rashid, K. H.; Redmer, C. F.; Ren, H. L.; Ripka, M.; Rong, G.; Ruan, X. D.; Santoro, V.; Sarantsev, A.; Savri, M.; Schoenning, K.; Schumann, S.; Shan, W.; Shao, M.; Shen, C. P.; Shen, P. X.; Shen, X. Y.; Sheng, H. Y.; Shepherd, M. R.; Song, W. M.; Song, X. Y.; Sosio, S.; Spataro, S.; Spruck, B.; Sun, G. X.; Sun, J. F.; Sun, S. S.; Sun, Y. J.; Sun, Y. Z.; Sun, Z. J.; Sun, Z. T.; Tang, C. J.; Tang, X.; Tapan, I.; Thorndike, E. H.; Tiemens, M.; Toth, D.; Ullrich, M.; Uman, I.; Varner, G. S.; Wang, B.; Wang, B. L.; Wang, D.; Wang, D. Y.; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, Q. J.; Wang, S. G.; Wang, W.; Wang, X. F.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z. H.; Wang, Z. Y.; Wei, D. H.; Wei, J. B.; Weidenkaff, P.; Wen, S. P.; Wiedner, U.; Wolke, M.; Wu, L. H.; Wu, Z.; Xia, L. G.; Xia, Y.; Xiao, D.; Xiao, Z. J.; Xie, Y. G.; Xiu, Q. L.; Xu, G. F.; Xu, L.; Xu, Q. J.; Xu, Q. N.; Xu, X. P.; Yan, L.; Yan, W. B.; Yan, W. C.; Yan, Y. H.; Yang, H. X.; Yang, L.; Yang, Y.; Yang, Y. X.; Ye, H.; Ye, M.; Ye, M. H.; Yin, J. H.; Yu, B. X.; Yu, C. X.; Yu, H. W.; Yu, J. S.; Yuan, C. Z.; Yuan, W. L.; Yuan, Y.; Yuncu, A.; Zafar, A. A.; Zallo, A.; Zeng, Y.; Zhang, B. X.; Zhang, B. Y.; Zhang, C.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J. J.; Zhang, J. L.; Zhang, J. Q.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, K.; Zhang, L.; Zhang, S. H.; Zhang, X. J.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. H.; Zhang, Z. H.; Zhang, Z. P.; Zhang, Z. Y.; Zhao, G.; Zhao, J. W.; Zhao, J. Y.; Zhao, J. Z.; Zhao, Lei; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, Q. W.; Zhao, S. J.; Zhao, T. C.; Zhao, Y. B.; Zhao, Z. G.; Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, W. J.; Zheng, Y. H.; Zhong, B.; Zhou, L.; Zhou, Li; Zhou, X.; Zhou, X. K.; Zhou, X. R.; Zhou, X. Y.; Zhu, K.; Zhu, K. J.; Zhu, S.; Zhu, X. L.; Zhu, Y. C.; Zhu, Y. S.

    2014-12-01

    Using a sample of 2.25 1 08 J /? events collected with the BESIII detector at the BEPCII collider, we search for the J /? semileptonic weak decay J /? ?Ds-e+?e+c .c . with a much higher sensitivity than previous searches. We also perform the first search for J /? ?Ds*-e+?e+c .c . No significant excess of a signal above background is observed in either channel. At the 90% confidence level, the upper limits are determined to be B (J /? ?Ds-e+?e+c .c .)<1.3 1 0-6 and B (J /? ?Ds* -e+?e+c .c .)<1.8 1 0-6 , respectively. Both are consistent with Standard Model predictions.

  17. 5. Historic American Buildings Survey C.C. Woodburn, Photographer. January 12, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. Historic American Buildings Survey C.C. Woodburn, Photographer. January 12, 1934 DETAIL OF ENTRANCE (WEST ELEVATION) - Ferdinand Daniel Pulver House, County Road F-70 Vicinity, Vandalia, Jasper County, IA

  18. C/C composite brake disk nondestructive evaluation by IR thermography

    NASA Astrophysics Data System (ADS)

    Chu, Tsuchin P.; Poudel, Anish; Filip, Peter

    2012-06-01

    This paper discusses the non-destructive evaluation of thick Carbon/Carbon (C/C) composite aircraft brake disks by using transient infrared thermography (IRT) approach. Thermal diffusivity measurement technique was applied to identify the subsurface anomalies in thick C/C brake disks. In addition, finite element analysis (FEA) modeling tool was used to determine the transient thermal response of the C/C disks that were subjected to flash heating. For this, series of finite element models were built and thermal responses with various thermal diffusivities subjected to different heating conditions were investigated. Experiments were conducted to verify the models by using custom built in-house IRT system and commercial turnkey system. The analysis and experimental results showed good correlation between thermal diffusivity value and anomalies within the disk. It was demonstrated that the step-heating transient thermal approach could be effectively applied to obtain the whole field thermal diffusivity value of C/C composites.

  19. Electronic and total energy properties of ternary and quaternary semiconductor compounds, alloys, and superlattices: Theoretical study of Cu/graphite bonding

    NASA Technical Reports Server (NTRS)

    Lambrecht, Walter R. L.

    1992-01-01

    The goals of the research were to provide a fundamental science basis for why the bonding of Cu to graphite is weak, to critically evaluate the previous analysis of the wetting studies with particular regard to the values used for the surface energies of Cu and graphite, and to make recommendations for future experiments or other studies which could advance the understanding and solution of this technological problem. First principles electronic structure calculations were used to study the problem. These are based on density functional theory in the local density approximation and the use of the linear muffin-tin orbital band structure method. Calculations were performed for graphite monolayers, single crystal graphite with the hexagonal AB stacking, bulk Cu, Cu(111) surface, and Cu/graphite superlattices. The study is limited to the basal plane of graphite because this is the graphite plane exposed to Cu and graphite surface energies and combined with the measured contact angles to evaluate the experimental adhesion energy.

  20. Spectroscopic investigation, natural bond orbital analysis, HOMO-LUMO and thermodynamic functions of 2-tert-butyl-5-methyl anisole using DFT (B3LYP) calculations.

    PubMed

    Balachandran, V; Santhi, G; Karpagam, V; Revathi, B; Karabacak, M

    2015-02-01

    The optimized molecular structure and corresponding vibrational assignments of 2-tert-butyl-5-methyl anisole (TBMA) have been investigated using density functional theory (DFT)/B3LYP with 6-31G(d,p) and 6-311++G(d,p) basis sets investigation of the relative orientation of the methoxy group has shown two conformers (O-cis) and (O-trans) exist. The vibrational analysis of the stable conformer of the title compound is performed by means of infrared absorption and Raman spectroscopy in combination with theoretical simultaneously. The natural bond orbital (NBO) analysis is useful to understand the intra-molecular hyper conjugative interaction lone pair and ?(?)(C-C), ?(?)(C-H) bond orbital. HOMO and LUMO energies show that charge transfer occurs in the molecule, therefore; HOMO, LUMO and molecular electrostatic potential (MEP) were calculated and analyzed. (1)H and (13)C NMR spectra by using gauge including atomic orbital (GIAO) method of studied compound were compared with experimental data. The thermodynamic functions of TBMA were calculated by B3LYP/6-311+G(d,p) basis set. PMID:25448946

  1. Chemical Bonding, again ionic bonding (in salts): transfer of e-

    E-print Network

    Zakarian, Armen

    Chemical Bonding, again ionic bonding (in salts): transfer of e- covalent bonding (organic molecules, non-metals): sharing e- metallic bonding: electron pooling (delocalization) Lewis electron 3A 4A 5A 6A 7A 8A 2 3 (exceptions) #12;Ionic Bonding Model See sample problem 9.1 4Na + O2 ! 2Na2O

  2. FIRST DETECTION OF c-C{sub 3}H{sub 2} IN A CIRCUMSTELLAR DISK

    SciTech Connect

    Qi Chunhua; Wilner, David J.; Rosenfeld, Katherine A.; Oeberg, Karin I.

    2013-03-01

    We report the first detection of c-C{sub 3}H{sub 2} in a circumstellar disk. The c-C{sub 3}H{sub 2} J = 6-5 line (217.882 GHz) is detected and imaged through Atacama Large Millimeter Array (ALMA) Science Verification observations toward the disk around the Herbig Ae star HD 163296 at 0.''8 resolution. The emission is consistent with that arising from a Keplerian rotating disk. Two additional c-C{sub 3}H{sub 2} transitions are also tentatively detected, bolstering the identification of this species, but with insufficient signal-to-noise ratio to constrain the spatial distribution. Using a previously developed model for the physical structure of this disk, we fit a radial power-law distribution model to the c-C{sub 3}H{sub 2} 6-5 emission and find that c-C{sub 3}H{sub 2} is present in a ring structure from an inner radius of about 30 AU to an outer radius of about 165 AU. The column density is estimated to be 10{sup 12}-10{sup 13} cm{sup -2}. The clear detection and intriguing ring structure suggest that c-C{sub 3}H{sub 2} has the potential to become a useful probe of radiation penetration in disks.

  3. Relativistic effects for the reaction Sg + 6 CO ? Sg(CO){sub 6}: Prediction of the mean bond energy, atomization energy, and existence of the first organometallic transactinide superheavy hexacarbonyl Sg(CO){sub 6}

    SciTech Connect

    Malli, Gulzari L.

    2015-02-14

    Our ab initio all-electron fully relativistic DiracFock (DF) and nonrelativistic (NR) Hartree-Fock calculations predict the DF relativistic and NR energies for the reaction: Sg + 6 CO ? Sg(CO){sub 6} as ?7.39 and ?6.96 eV, respectively, i.e., our calculated ground state total DF relativistic and NR energies for the reaction product Sg(CO){sub 6} are lower by 7.39 and 6.96 eV than the total DF and NR ground state energies of the reactants, viz., one Sg atom plus six CO molecules, respectively. Our calculated DF relativistic and NR atomization energies (Ae) are 65.23 and 64.82 eV, respectively, and so the contribution of relativistic effects to the Ae of ?0.40 eV is marginal. The SgC and CO optimized bond distances for the octahedral geometry as calculated in our DF (NR) calculations are 2.151 (2.318 ) and 1.119 (1.114 ), respectively. The BSSE correction calculated using the DIRAC code ?14 kcal/mol. The relativistic DF and NR mean energies predicted by us are 118.8 and 111.9 kJ/mol, respectively, and the contribution of ?7 kJ/mol due to relativistic effects to the mean energy of Sg(CO){sub 6} is negligible. Ours are the first calculations of the relativistic effects for the atomization energy, mean bond energy, and energy of the reaction for possible formation of Sg(CO){sub 6}, and both our relativistic DF and the NR treatments clearly predict for the first time the existence of hexacarbonyl of the transactinide superheavy element seaborgium Sg. In conclusion, relativistic effects are not significant for Sg(CO){sub 6}.

  4. Relativistic effects for the reaction Sg + 6 CO ? Sg(CO)6: Prediction of the mean bond energy, atomization energy, and existence of the first organometallic transactinide superheavy hexacarbonyl Sg(CO)6

    NASA Astrophysics Data System (ADS)

    Malli, Gulzari L.

    2015-02-01

    Our ab initio all-electron fully relativistic Dirac-Fock (DF) and nonrelativistic (NR) Hartree-Fock calculations predict the DF relativistic and NR energies for the reaction: Sg + 6 CO ? Sg(CO)6 as -7.39 and -6.96 eV, respectively, i.e., our calculated ground state total DF relativistic and NR energies for the reaction product Sg(CO)6 are lower by 7.39 and 6.96 eV than the total DF and NR ground state energies of the reactants, viz., one Sg atom plus six CO molecules, respectively. Our calculated DF relativistic and NR atomization energies (Ae) are 65.23 and 64.82 eV, respectively, and so the contribution of relativistic effects to the Ae of 0.40 eV is marginal. The Sg-C and C-O optimized bond distances for the octahedral geometry as calculated in our DF (NR) calculations are 2.151 (2.318 ) and 1.119 (1.114 ), respectively. The BSSE correction calculated using the DIRAC code 14 kcal/mol. The relativistic DF and NR mean energies predicted by us are 118.8 and 111.9 kJ/mol, respectively, and the contribution of 7 kJ/mol due to relativistic effects to the mean energy of Sg(CO)6 is negligible. Ours are the first calculations of the relativistic effects for the atomization energy, mean bond energy, and energy of the reaction for possible formation of Sg(CO)6, and both our relativistic DF and the NR treatments clearly predict for the first time the existence of hexacarbonyl of the transactinide superheavy element seaborgium Sg. In conclusion, relativistic effects are not significant for Sg(CO)6.

  5. Relativistic effects for the reaction Sg + 6 CO ? Sg(CO)6: Prediction of the mean bond energy, atomization energy, and existence of the first organometallic transactinide superheavy hexacarbonyl Sg(CO)6.

    PubMed

    Malli, Gulzari L

    2015-02-14

    Our ab initio all-electron fully relativistic Dirac-Fock (DF) and nonrelativistic (NR) Hartree-Fock calculations predict the DF relativistic and NR energies for the reaction: Sg + 6 CO ? Sg(CO)6 as -7.39 and -6.96 eV, respectively, i.e., our calculated ground state total DF relativistic and NR energies for the reaction product Sg(CO)6 are lower by 7.39 and 6.96 eV than the total DF and NR ground state energies of the reactants, viz., one Sg atom plus six CO molecules, respectively. Our calculated DF relativistic and NR atomization energies (Ae) are 65.23 and 64.82 eV, respectively, and so the contribution of relativistic effects to the Ae of ?0.40 eV is marginal. The Sg-C and C-O optimized bond distances for the octahedral geometry as calculated in our DF (NR) calculations are 2.151 (2.318 ) and 1.119 (1.114 ), respectively. The BSSE correction calculated using the DIRAC code ?14 kcal/mol. The relativistic DF and NR mean energies predicted by us are 118.8 and 111.9 kJ/mol, respectively, and the contribution of ?7 kJ/mol due to relativistic effects to the mean energy of Sg(CO)6 is negligible. Ours are the first calculations of the relativistic effects for the atomization energy, mean bond energy, and energy of the reaction for possible formation of Sg(CO)6, and both our relativistic DF and the NR treatments clearly predict for the first time the existence of hexacarbonyl of the transactinide superheavy element seaborgium Sg. In conclusion, relativistic effects are not significant for Sg(CO)6. PMID:25681910

  6. The dissociative bond.

    PubMed

    Gordon, Nirit

    2013-01-01

    Dissociation leaves a psychic void and a lingering sense of psychic absence. How do 2 people bond while they are both suffering from dissociation? The author explores the notion of a dissociative bond that occurs in the aftermath of trauma--a bond that holds at its core an understanding and shared detachment from the self. Such a bond is confined to unspoken terms that are established in the relational unconscious. The author proposes understanding the dissociative bond as a transitional space that may not lead to full integration of dissociated knowledge yet offers some healing. This is exemplified by R. Prince's (2009) clinical case study. A relational perspective is adopted, focusing on the intersubjective aspects of a dyadic relationship. In the dissociative bond, recognition of the need to experience mutual dissociation can accommodate a psychic state that yearns for relationship when the psyche cannot fully confront past wounds. Such a bond speaks to the need to reestablish a sense of human relatedness and connection when both parties in the relationship suffer from disconnection. This bond is bound to a silence that becomes both a means of protection against the horror of traumatic memory and a way to convey unspoken gestures toward the other. PMID:23282044

  7. Mother-Child Bonding.

    ERIC Educational Resources Information Center

    Pearce, Joseph Chilton

    1994-01-01

    Examines the nature of mother-child bonding from the prenatal stage through early infancy, discussing how the mother's actions, even before birth, stimulate her child's senses. Explains the crucial role that physical contact, breastfeeding, and visual stimuli have on mother-child bonding in human and animal newborns. (MDM)

  8. Shape Bonding method

    NASA Technical Reports Server (NTRS)

    Pontius, James T. (Inventor)

    2010-01-01

    The present invention is directed to a method of bonding at least two surfaces together. The methods step of the present invention include applying a strip of adhesive to a first surface along a predefined outer boundary of a bond area and thereby defining a remaining open area there within. A second surface, or gusset plate, is affixed onto the adhesive before the adhesive cures. The strip of adhesive is allowed to cure and then a second amount of adhesive is applied to cover the remaining open area and substantially fill a void between said first and second surfaces about said bond area. A stencil may be used to precisely apply the strip of adhesive. When the strip cures, it acts as a dam to prevent overflow of the subsequent application of adhesive to undesired areas. The method results in a precise bond area free of undesired shapes and of a preferred profile which eliminate the drawbacks of the prior art bonds.

  9. Wood Bond Testing

    NASA Technical Reports Server (NTRS)

    1989-01-01

    A joint development program between Hartford Steam Boiler Inspection Technologies and The Weyerhaeuser Company resulted in an internal bond analyzer (IBA), a device which combines ultrasonics with acoustic emission testing techniques. It is actually a spinoff from a spinoff, stemming from a NASA Lewis invented acousto-ultrasonic technique that became a system for testing bond strength of composite materials. Hartford's parent company, Acoustic Emission Technology Corporation (AET) refined and commercialized the technology. The IBA builds on the original system and incorporates on-line process control systems. The IBA determines bond strength by measuring changes in pulsar ultrasonic waves injected into a board. Analysis of the wave determines the average internal bond strength for the panel. Results are displayed immediately. Using the system, a mill operator can adjust resin/wood proportion, reduce setup time and waste, produce internal bonds of a consistent quality and automatically mark deficient products.

  10. Biomass Oxidation: Formyl C-H Bond Activation by the Surface Lattice Oxygen of Regenerative CuO Nanoleaves.

    PubMed

    Amaniampong, Prince N; Trinh, Quang Thang; Wang, Bo; Borgna, Armando; Yang, Yanhui; Mushrif, Samir H

    2015-07-27

    An integrated experimental and computational investigation reveals that surface lattice oxygen of copper oxide (CuO) nanoleaves activates the formyl C-H bond in glucose and incorporates itself into the glucose molecule to oxidize it to gluconic acid. The reduced CuO catalyst regains its structure, morphology, and activity upon reoxidation. The activity of lattice oxygen is shown to be superior to that of the chemisorbed oxygen on the metal surface and the hydrogen abstraction ability of the catalyst is correlated with the adsorption energy. Based on the present investigation, it is suggested that surface lattice oxygen is critical for the oxidation of glucose to gluconic acid, without further breaking down the glucose molecule into smaller fragments, because of C-C cleavage. Using CuO nanoleaves as catalyst, an excellent yield of gluconic acid is also obtained for the direct oxidation of cellobiose and polymeric cellulose, as biomass substrates. PMID:26119659

  11. Anharmonic vibrational spectra of hydrogen bonded clusters: Comparison between higher energy derivative and mean-field grid based methods

    SciTech Connect

    Xantheas, Sotiris S.

    2006-10-01

    We present a critical comparison between two different approaches for calculating anharmonic frequencies, namely grid-based fitting methods (VSCF, CC-VSCF, VCI) and the ones obtained by second-order perturbation theory from the third and fourth energy derivatives. We report the results for the anharmonic frequencies with the two approaches for the F-(H2O), Cl-(H2O), HNO3 and HNO3(H2O) molecular systems at the same level of theory and basis set. The two methods were found to produce results of similar accuracy for the fundamental band origins and selected overtone and combination bands. The optimal equilibrium and vibrationally averaged geometries, spectroscopic constants and anharmonic frequencies of the (HF)n, n=2-4 clusters are reported at the MP2/aug-cc-pVDZ level of theory based on calculations of higher energy derivatives. This work was performed under the auspices of the Division of Chemical Sciences, Geosciences and Biosciences, Office of Science, US Department of Energy with Battelle Memorial Institute, which operates the Pacific Northwest National Laboratory. Computer resources at the National Energy Research Scientific Computer Center (NERSC) were provided by the Division of Chemical Sciences Geosciences and Biosciences, US Department of Energy.

  12. Spectroscopic and thermochemical properties of the c-C6H7 radical: A high-level theoretical study

    NASA Astrophysics Data System (ADS)

    Bargholz, Arne; Oswald, Rainer; Botschwina, Peter

    2013-01-01

    The electronic ground state (tilde X{}^2B_1) of the cyclohexadienyl radical (c-C6H7) has been studied by explicitly correlated coupled cluster theory at the RCCSD(T)-F12x (x = a, b) level, partly in combination with the double-hybrid density functional method B2PLYP. An accurate equilibrium structure has been established and the ground-state rotational constants are predicted to be A0 = 5347.3 MHz, B0 = 5249.7 MHz, and C0 = 2692.5 MHz. The calculated vibrational wavenumbers agree well with the recent p-H2 matrix IR data [M. Bahou, Y.-J. Wu, and Y.-P. Lee, J. Chem. Phys. 136, 154304 (2012), 10.1063/1.3703502] and several predictions have been made. A low value of 6.803 0.005 eV is predicted for the adiabatic ionization energy of c-C6H7. Owing to a moderately large change in the equilibrium structure upon ionization, the first band of the photoelectron spectrum is dominated by the adiabatic peak (100%) and only the peaks corresponding to excitation of the two lowest totally symmetric vibrations (?12 and ?11) by one vibrational quantum have relative intensities of more than 15%. The C6H6-H dissociation energy is calculated to be D0 = 85.7 kJ mol-1, with an estimated error of 2 kJ mol-1.

  13. Anisotropic Collective Flow of Lambda Hyperons Produced in C + C Collisions at 4.2 AGeV/c

    E-print Network

    L. Chkhaidze; P. Danielewicz; T. Djobava; L. Kharkhelauri; E. Kladnitskaya

    2009-08-01

    Features of anisotropic collective flow and spectral temperatures have been determined for lambda hyperons emitted from C + C collisions, at incident momentum of 4.2 AGeV/c, measured using the Propane Bubble Chamber of JINR at Dubna. Moreover, characteristics of protons and of negative pions, emitted from those collisions, have been determined and provided for comparison. The directed and elliptic flows of lambdas both agree in sign with the corresponding flows of protons. Parameters of the directed and elliptic flows for lambdas agree further, within errors, with the corresponding parameters for the co-produced protons. This contrasts an earlier finding by the E895 Collaboration of the directed flow being significantly weaker for lambdas than protons, in the much heavier Au + Au system, at comparable incident momentum. Particle spectral temperatures in the C + C collisions have been determined focusing independently on either center-of-mass energy, transverse energy or transverse momentum distributions. For either protons or negative pions, the temperatures were found to be approximately the same, no matter whether the emission of those particles was associated with lambda production or not. Results of the measurements have been compared to the results of simulations within the Quark-Gluon String Model.

  14. A Semi-Analytical Method for Determining the Energy Release Rate of Cracks in Adhesively-Bonded Single-Lap Composite Joints

    NASA Technical Reports Server (NTRS)

    Yang, Charles; Sun, Wenjun; Tomblin, John S.; Smeltzer, Stanley S., III

    2007-01-01

    A semi-analytical method for determining the strain energy release rate due to a prescribed interface crack in an adhesively-bonded, single-lap composite joint subjected to axial tension is presented. The field equations in terms of displacements within the joint are formulated by using first-order shear deformable, laminated plate theory together with kinematic relations and force equilibrium conditions. The stress distributions for the adherends and adhesive are determined after the appropriate boundary and loading conditions are applied and the equations for the field displacements are solved. Based on the adhesive stress distributions, the forces at the crack tip are obtained and the strain energy release rate of the crack is determined by using the virtual crack closure technique (VCCT). Additionally, the test specimen geometry from both the ASTM D3165 and D1002 test standards are utilized during the derivation of the field equations in order to correlate analytical models with future test results. The system of second-order differential field equations is solved to provide the adherend and adhesive stress response using the symbolic computation tool, Maple 9. Finite element analyses using J-integral as well as VCCT were performed to verify the developed analytical model. The finite element analyses were conducted using the commercial finite element analysis software ABAQUS. The results determined using the analytical method correlated well with the results from the finite element analyses.

  15. TiCl, TiH and TiH+ Bond Energies, a Test of a Correlation Consistent Ti Basis Set

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Arnold, James O. (Technical Monitor)

    1999-01-01

    Correlation consistent basis sets are developed for Ti atom. The polarization functions are optimized for the average of the 3F and 5F states. One series of correlation consistent basis sets is for 3d and 4s correlation, while the second series includes 3s and 3p correlation as well as 3d and 4s correlation. These basis sets are tested using the Ti 3F-5F separation and the dissociation energies of TiCl X4Phi, TiH X4Phi, and TiH(+) X3Phi. The CCSD(T) complete basis set limit values are determined by extrapolation. The Douglas Kroll approach is used to compute the scalar relativistic effect. Spin-orbit effects are taken from experiment and/or computed at the CASSCF level. The Ti 3F-5F separation is in excellent agreement with experiment, while the TiCl, TiH, and TiH(+) bond energies are in good agreement with experiment. Extrapolation with the valence basis set is consistent with other atoms, while including 3s and 3p correlation appears to make extrapolation.

  16. Energy and power modeling of multi mode lamb waves propagating in structure bonded with piezoelectric wafer active sensors

    NASA Astrophysics Data System (ADS)

    Kamal, Ayman; Lin, Bin; Giurgiutiu, Victor

    2013-01-01

    This paper presents a model for energy transfer between piezoelectric wafer active sensor (PWAS) and excited structures. Analytical models are developed for PWAS admittance, active power, Lamb waves kinetic, potential energies, and power. This model is based on Lamb waves; accordingly it is valid for high frequency multi-modal excitation analysis. Numerical simulation is done for (a) thin aluminum plate, where only first symmetric and antisymmetric exist, and (b) thick steel plate example is presented to show the case of multi-modal wave propagation. Parametric studies for different excitation frequencies and different transducer sizes are done to show the best match of (frequency/PWAS size) for exciting structures.

  17. A benchmark database for adsorption bond energies to transition metal surfaces and comparison to selected DFT functionals

    NASA Astrophysics Data System (ADS)

    Wellendorff, Jess; Silbaugh, Trent L.; Garcia-Pintos, Delfina; Nrskov, Jens K.; Bligaard, Thomas; Studt, Felix; Campbell, Charles T.

    2015-10-01

    We present a literature collection of experimental adsorption energies over late transition metal surfaces for systems where we believe the energy measurements are particularly accurate, and the atomic-scale adsorption geometries are particularly well established. We propose that this could become useful for benchmarking theoretical methods for calculating adsorption processes. We compare the experimental results to six commonly used electron density functionals, including some (RPBE, BEEF-vdW) which were specifically developed to treat adsorption processes. The comparison shows that there is ample room for improvements in the theoretical descriptions.

  18. Metal cation dependence of interactions with amino acids: bond dissociation energies of Rb(+) and Cs(+) to the acidic amino acids and their amide derivatives.

    PubMed

    Armentrout, P B; Yang, Bo; Rodgers, M T

    2014-04-24

    Metal cation-amino acid interactions are key components controlling the secondary structure and biological function of proteins, enzymes, and macromolecular complexes comprising these species. Determination of pairwise interactions of alkali metal cations with amino acids provides a thermodynamic vocabulary that begins to quantify these fundamental processes. In the present work, we expand a systematic study of such interactions by examining rubidium and cesium cations binding with the acidic amino acids (AA), aspartic acid (Asp) and glutamic acid (Glu), and their amide derivatives, asparagine (Asn) and glutamine (Gln). These eight complexes are formed using electrospray ionization and their bond dissociation energies (BDEs) are determined experimentally using threshold collision-induced dissociation with xenon in a guided ion beam tandem mass spectrometer. Analyses of the energy-dependent cross sections include consideration of unimolecular decay rates, internal energy of the reactant ions, and multiple ion-neutral collisions. Quantum chemical calculations are conducted at the B3LYP, MP2(full), and M06 levels of theory using def2-TZVPPD basis sets, with results showing reasonable agreement with experiment. At 0 and 298 K, most levels of theory predict that the ground-state conformers for M(+)(Asp) and M(+)(Asn) involve tridentate binding of the metal cation to the backbone carbonyl, amino, and side-chain carbonyl groups, although tridentate binding to the carboxylic acid group and side-chain carbonyl is competitive for M(+)(Asn). For the two longer side-chain amino acids, Glu and Gln, multiple structures are competitive. A comparison of these results to those for the smaller alkali cations, Na(+) and K(+), provides insight into the trends in binding energies associated with the molecular polarizability and dipole moment of the side chain. For all four metal cations, the BDEs are inversely correlated with the size of the metal cation and follow the order Asp < Glu < Asn < Gln. PMID:24528155

  19. Interfacial Bond-Breaking Electron Transfer in Mixed WaterEthylene Glycol Solutions: Reorganization Energy and Interplay between Different Solvent Modes

    PubMed Central

    2013-01-01

    We explore solvent dynamics effects in interfacial bond breaking electron transfer in terms of a multimode approach and make an attempt to interpret challenging recent experimental results (the nonmonotonous behavior of the rate constant of electroreduction of S2O82 from mixed waterEG solutions when increasing the EG fraction; see Zagrebin, P.A. et al. J. Phys. Chem. B2010, 114, 311). The exact expansion of the solvent correlation function (calculated using experimental dielectric spectra) in a series predicts the splitting of solvent coordinate in three independent modes characterized by different relaxation times. This makes it possible to construct a 5D free-energy surface along three solvent coordinates and one intramolecular degree of freedom describing first electron transfer at the reduction of a peroxodisulphate anion. Classical molecular dynamics simulations were performed to study the solvation of a peroxodisulphate anion (S2O82) in oxidized and reduced states in pure water and ethylene glycol (EG) as well as mixed H2OEG solutions. The solvent reorganization energy of the first electron-transfer step at the reduction of S2O82 was calculated for several compositions of the mixed solution. This quantity was found to be significantly asymmetric. (The reorganization energies of reduction and oxidation differ from each other.) The averaged reorganization energy slightly increases with increasing the EG content in solution. This finding clearly indicates that for the reaction under study the static solvent effect no longer competes with solvent dynamics. Brownian dynamics simulations were performed to calculate the electron-transfer rate constants as a function of the solvent composition. The results of the simulations explain the experimental data, at least qualitatively. PMID:23768162

  20. Effectiveness of Diffusion Barrier Coatings for Mo-Re Embedded in C/SiC and C/C

    NASA Technical Reports Server (NTRS)

    Glass, David E.; Shenoy, Ravi N.; Wang, Zeng-Mei; Halbig, Michael C.

    2001-01-01

    Advanced high-temperature cooling applications may often require the elevated-temperature capability of carbon/silicon carbide or carbon/carbon composites in combination with the hermetic capability of metallic tubes. In this paper, the effects of C/SiC and C/C on tubes fabricated from several different refractory metals were evaluated. Though Mo, Nb, and Re were evaluated in the present study, the primary effort was directed toward two alloys of Mo-Re, namely, arc cast Mo-41Re and powder metallurgy Mo-47.5Re. Samples of these refractory metals were subjected to either the PyC/SiC deposition or embedding in C/C. MoSi2(Ge), R512E, and TiB2 coatings were included on several of the samples as potential diffusion barriers. The effects of the processing and thermal exposure on the samples were evaluated by conducting burst tests, microhardness surveys, and scanning electron microscopic examination (using either secondary electron or back scattered electron imaging and energy dispersive spectroscopy). The results showed that a layer of brittle Mo-carbide formed on the substrates of both the uncoated Mo-41Re and the uncoated Mo-47.5Re, subsequent to the C/C or the PyC/SiC processing. Both the R512E and the MoSi2(Ge) coatings were effective in preventing not only the diffusion of C into the Mo-Re substrate, but also the formation of the Mo-carbides. However, none of the coatings were effective at preventing both C and Si diffusion without some degradation of the substrate.

  1. Design, Syntheses and Biological Applications of Through-bond Energy Transfer Cassettes and Novel Non-covalently Cell Penetrating Peptides

    E-print Network

    Han, Junyan

    2012-02-14

    A xanthene-BODIPY cassette is used as a ratiometric intracellular pH reporter for imaging protein-dye conjugates in living cells. A model was hypothesized to explain the pH-dependent energy transfer efficiencies from the donor to the acceptor based...

  2. Isotope dependent, temperature regulated, energy repartitioning in a low-barrier, short-strong hydrogen bonded cluster

    E-print Network

    Iyengar, Srinivasan S.

    Isotope dependent, temperature regulated, energy repartitioning in a low-barrier, short, Bloomington, IN 47405 Abstract We investigate and analyze the vibrational properties, including H/D isotope between simulated cluster spectroscopy of the isotopically labeled systems were analyzed from a system

  3. Wafer-Level Thermocompression Bonds

    E-print Network

    Tsau, Christine H.

    Thermocompression bonding of gold is a promising technique for achieving low temperature, wafer-level bonding without the application of an electric field or complicated pre-bond cleaning procedure. The presence of a ductile ...

  4. Metallacyclocumulenes: a theoretical perspective on the structure, bonding, and reactivity.

    PubMed

    Roy, Subhendu; Rosenthal, Uwe; Jemmis, Eluvathingal D

    2014-10-21

    Conspectus Transition metals help to stabilize highly strained organic fragments. Metallacycles, especially unsaturated ones, provide much variety in this area. We had a sustained interest in understanding new C-C bond formation reactions affected by binuclear transition metal fragments Cp2M. One such study led to the exploration of the bimetallic C-C cleavage and coupled complexes, where the acetylide ligands bridge two metal atoms. The underlying M-C interaction in these complexes inspired the synthesis of a five-membered cyclocumulene complex, which opened a new phase in organometallic chemistry. The metallacyclocumulene produces a variety of C-C cleavage and coupled products including a radialene complex. Group 4 metallocenes have thus unlocked a fascinating chemistry by stabilizing strained unsaturated C4 organic fragments in the form of five-membered metallacyclocumulenes, metallacyclopentynes, and metallacycloallenes. Over the years, we have carried out a comprehensive theoretical study to understand the unusual stability and reactivity of these metallacycles. The unique (M-C?) interaction of the internal carbon atoms with the metal atom is the reason for unusual stability of the metallacycles. We have also shown that there is a definite dependence of the C-C coupling and cleavage reactions on the metal of metallacyclocumulenes. It demonstrates unexpected reaction pathways for these reactions. Based on this understanding, we have predicted and unraveled the stabilization factors of an unusual four-membered metallacycloallene complex. Indeed, our prediction about a four-membered heterometallacycle has led to an interesting bonding situation, which is experimentally realized. This type of M-C bonding is intriguing from a fundamental perspective and has great relevance in synthesizing unusual structures with interesting properties. In this Account, we first give a short prologue of what led to the present study and describe the salient features of the structure and bonding of the metallacyclocumulenes. The unusual reaction pathway of this metallacycle is explored next. Similar features of the metallacyclopentynes and metallacycloallenes are briefly mentioned. Then, we discuss the exploitation of the unique M-C bonding to design some exotic molecules such as a four-membered metallacycloallene complex. Our efforts to build a conceptual framework to understand these metallacycles and to exploit their chemistry continue. PMID:25171518

  5. Comparative study of halogen- and hydrogen-bond interactions between benzene derivatives and dimethyl sulfoxide.

    PubMed

    Zheng, Yan-Zhen; Deng, Geng; Zhou, Yu; Sun, Hai-Yuan; Yu, Zhi-Wu

    2015-08-24

    The halogen bond, similar to the hydrogen bond, is an important noncovalent interaction and plays important roles in diverse chemistry-related fields. Herein, bromine- and iodine-based halogen-bonding interactions between two benzene derivatives (C6 F5 Br and C6 F5 I) and dimethyl sulfoxide (DMSO) are investigated by using IR and NMR spectroscopy and ab initio calculations. The results are compared with those of interactions between C6 F5 Cl/C6 F5 H and DMSO. First, the interaction energy of the hydrogen bond is stronger than those of bromine- and chlorine-based halogen bonds, but weaker than iodine-based halogen bond. Second, attractive energies depend on 1/r(n) , in which n is between three and four for both hydrogen and halogen bonds, whereas all repulsive energies are found to depend on 1/r(8.5) . Third, the directionality of halogen bonds is greater than that of the hydrogen bond. The bromine- and iodine-based halogen bonds are strict in this regard and the chlorine-based halogen bond only slightly deviates from 180. The directional order is iodine-based halogen bond>bromine-based halogen bond>chlorine-based halogen bond>hydrogen bond. Fourth, upon the formation of hydrogen and halogen bonds, charge transfers from DMSO to the hydrogen- and halogen-bond donors. The CH3 group contributes positively to stabilization of the complexes. PMID:26118800

  6. Influence of crystal habit on the surface free energy and interparticulate bonding of L-lysine monohydrochloride dihydrate.

    PubMed

    Bandyopadhyay, R; Grant, D J

    2000-01-01

    The objective of the present study was to apply a technique to measure the surface energy of crystalline powders without changing the surface properties by compaction, and to relate such measurements to crystal habit and orientation. The surface free energy of uncompacted L-lysine monohydrochloride dihydrate (LH), determined using a modified sessile-drop method, reflected a combined value for the various faces, and was influenced by the relative size of the faces and the orientation of the crystals. The surface free energy values obtained from contact angle measurements were within the possible range calculated from the crystal structure. Discrepancies between the theoretical estimates of interparticulate cohesive strengths and those measured from the tensile strength of powder compacts were used to estimate the flaw sizes (or gaps between the particles) that act as stress concentrators and reduce the tensile strength of the compacts. The flaw sizes indicate packing and compressibility of the various crystal habits. In the absence of compressive load, compacts made out of the equidimensional crystals have the larger flaw sizes (wider cracks or wider gaps between the particles). At higher compaction pressures, the compacts from long rod-shaped crystals have longer crack lengths. The weakness of the compacts made from the long rods at the higher compaction pressures may be because of the longer crack length along the interparticulate boundary, which may result in a higher stress intensity at the crack tip and increased fracture propensity. PMID:10669915

  7. Prompt J /? production in association with a c c pair within the framework of nonrelativistic QCD via photon-photon collisions at the International Linear Collider

    NASA Astrophysics Data System (ADS)

    Sun, Zhan; Wu, Xing-Gang; Zhang, Hong-Fei

    2015-10-01

    We present a systematical study on the prompt J /? production in association with a c c pair via the process, ? ? ?H (c c )+c +c , within the framework of nonrelativistic QCD at the future high-energy e+e- colliderInternational Linear Collider (ILC), including both direct and feed-down contributions. For direct J /? production, the states with color-octet channels, especially the P3 J[8] and S1 0[8] ones, provide a dominant contribution to the production cross section, which are about 52 times over that of the color-singlet one. This is clearly shown by the transverse momentum (pt) and rapidity distributions. The feed-down contribution from ?' and ?c J (J =0 , 1, 2) is sizable, which is about 20% to the total prompt cross section. Besides the yields, we also calculate the J /? polarization parameter ? . In the small pt region, the polarization of the prompt J /? is longitudinal due to large contributions through the P3 J[8] channel, and becomes transverse in the high pt region due to the S3 1[8] channel. Thus the J /? production via photon-photon collisions at the ILC shall provide a useful platform for testing the color-octet mechanism.

  8. Chemical bonding and electronic structures of the Al2SiO5 polymorphs, andalusite, sillimanite, and kyanite: X-ray photoelectron- and electron energy loss spectroscopy studies

    SciTech Connect

    Ohuchi, Fumio S.; Ghose, Subrata; Engelhard, Mark H.; Baer, Donald R.

    2006-05-01

    We have undertaken a detailed analysis of the X-ray photoelectron spectra obtained from the three polymorphs of Al2SiO5; andalusite, sillimanite, and kyanite. Comparison of the spectra was made based on the chemical bonding and structural differences in the Al- and Si-coordination within each polymorph. The spectra for Si(2p) for all three polymorphs are nearly identical, consistent with the fact that all the Si atoms are in 4-fold (tetrahedral) coordination, whereas the binding energies, peak shapes, and peak widths for Al(2p) vary depending on the type of polymorph. The upper-valence band for all three polymorphs is characterized by four main features derived from O(2p), Al(3s), Al(2p), Si(3s), and Si(3p), and the differences in their contributions are observed. The density of state of the Al2SiO5 polymorphs is relatively featureless compared to those observed from ?-SiO2 and ?-Al2O3, suggesting that the orbital overlaps span a greater range in energy. The observed band gap energy for Al2SiO5 (sillimanite) was {approx}9.1eV, a value in between those for ?-SiO2 ({approx}8.6eV) and ?-Al2O3 ({approx}9.6eV). The conduction band feature of Al2SiO5 was experimentally compared to those of ?-SiO2 and ?-Al2O3, and shown that it is indeed intermediate between the ?-SiO2 and ?-Al2O3 phases.

  9. The effect of pi-stacking, h-bonding, and electrostatic interactions on the ionization energies of nucleic acid bases: adenine-adenine, thymine-thymine and adenine-thymine dimers

    SciTech Connect

    Bravaya, Ksenia B.; Kostko, Oleg; Ahmed, Musahid; Krylov, Anna I.

    2009-09-02

    A combined theoretical and experimental study of the ionized dimers of thymine and adenine, TT, AA, and AT, is presented. Adiabatic and vertical ionization energies(IEs) for monomers and dimers as well as thresholds for the appearance of the protonated species are reported and analyzed. Non-covalent interactions stronglyaffect the observed IEs. The magnitude and the nature of the effect is different for different isomers of the dimers. The computations reveal that for TT, the largestchanges in vertical IEs (0.4 eV) occur in asymmetric h-bonded and symmetric pi- stacked isomers, whereas in the lowest-energy symmetric h-bonded dimer the shiftin IEs is much smaller (0.1 eV). The origin of the shift and the character of the ionized states is different in asymmetric h-bonded and symmetric stacked isomers. Inthe former, the initial hole is localized on one of the fragments, and the shift is due to the electrostatic stabilization of the positive charge of the ionized fragment by thedipole moment of the neutral fragment. In the latter, the hole is delocalized, and the change in IE is proportional to the overlap of the fragments' MOs. The shifts in AAare much smaller due to a less effcient overlap and a smaller dipole moment. The ionization of the h-bonded dimers results in barrierless (or nearly barrierless) protontransfer, whereas the pi-stacked dimers relax to structures with the hole stabilized by the delocalization or electrostatic interactions.

  10. Application of polarizable ellipsoidal force field model to pnicogen bonds.

    PubMed

    Liu, Fang; Du, Likai; Gao, Jun; Wang, Lili; Song, Bo; Liu, Chengbu

    2015-03-15

    Noncovalent interactions, such as hydrogen bonds and halogen bonds, are frequently used in drug designing and crystal engineering. Recently, a novel noncovalent pnicogen bonds have been identified as an important driving force in crystal structures with similar bonding mechanisms as hydrogen bond and halogen bond. Although the pnicogen bond is highly anisotropic, the pnicogen bond angles range from 160 to 180 due to the complicated substituent effects. To understand the anisotropic characters of pnicogen bond, a modification of the polarizable ellipsoidal force field (PEff) model previously used to define halogen bonds was proposed in this work. The potential energy surfaces (PESs) of mono- and polysubstituted PH3 -NH3 complexes were calculated at CCSD(T), MP2, and density functional theory levels and were used to examine the modified PEff model. The results indicate that the modified PEff model can precisely characterize pnicogen bond. The root mean squared error of PES obtained with PEff model is less than 0.5 kcal/mol, compared with MP2 results. In addition, the modified PEff model may be applied to other noncovalent bond interactions, which is important to understand the role of intermolecular interactions in the self-assembly structures. PMID:25565043

  11. Detecting Defective Solder Bonds

    NASA Technical Reports Server (NTRS)

    Paulson, R.; Barney, J.; Decker, H. J.

    1984-01-01

    Method is noncontact and nondestructive. Technique detects solder bonds in solar array of other large circuit board, using thermal-imaging camera. Board placed between heat lamp and camera. Poor joints indiated by "cold" spots on the infrared image.

  12. Gold Thermocompression Wafer Bonding

    E-print Network

    Spearing, S. Mark

    Thermocompression bonding of gold is a promising technique for the fabrication and packaging microelectronic and MEMS devices. The use of a gold interlayer and moderate temperatures and pressures results in a hermetic, ...

  13. Characterization of anodic bonding

    E-print Network

    Tudryn, Carissa Debra, 1978-

    2004-01-01

    Anodic bonding is a common process used in MicroElectroMechanical Systems (MEMS) device fabrication and packaging. Polycrystalline chemical vapor deposited (CVD) silicon carbide (SiC) is emerging as a new MEMS device and ...

  14. First observation of the isospin violating decay J/??????+c.c.

    DOE PAGESBeta

    Ablikim, M.; Achasov, M. N.; Ambrose, D. J.; An, F. F.; An, Q.; An, Z. H.; Bai, J. Z.; Ban, Y.; Becker, J.; Berger, N.; et al

    2012-08-15

    Using a sample of (225.22.8)10? J/? events collected with the BESIII detector, we present results of a study of J/????? and report the first observation of the isospin violating decay J/?????+c.c., in which ?? decays to ??. The measured branching fractions are B(J/?????)=(1.460.110.12)10?? and B(J/?????)=(1.370.120.11)10??. We search for ?(1520)??? decay, and find no evident signal, and an upper limit for the product branching fraction B(J/????(1520)+c.c.)B(?(1520)???)c??? in J/????c, ?c??? and measure the branching fraction B(?c???)=(1.160.12(stat)0.19(syst)0.28(PDG))10?.

  15. Correlating Infrared and X-ray Absorption Energies for Molecular-Level Insight into Hydrogen Bond Making and Breaking in Solution.

    PubMed

    Prmont-Schwarz, Mirabelle; Schreck, Simon; Iannuzzi, Marcella; Nibbering, Erik T J; Odelius, Michael; Wernet, Philippe

    2015-06-25

    While ubiquitous, the making and breaking of hydrogen bonds in solution is notoriously difficult to study due to the associated complex changes of nuclear and electronic structures. With the aim to reduce the according uncertainty in correlating experimental observables and hydrogen-bond configurations, we combine the information from proximate methods to study the N-HO hydrogen bond in solution. We investigate hydrogen-bonding of the N-H group of N-methylaniline with oxygen from liquid DMSO and acetone with infrared spectra in the N-H stretching region and X-ray absorption spectra at the N K-edge. We experimentally observe blue shifts of the infrared stretching band and an X-ray absorption pre-edge peak when going from DMSO to acetone. With ab initio molecular dynamics simulations and calculated spectra, we qualitatively reproduce the experimental observables but we do not reach quantitative agreement with experiment. The infrared spectra support the notion of weakening the N-HO hydrogen bond from DMSO to acetone. However, we fail to theoretically reproduce the measured shift of the X-ray absorption pre-edge peak. We discuss possible shortcomings of the simulation models and spectrum calculations. Common features and distinct differences with the O-HO hydrogen bond are highlighted, and the implications for monitoring hydrogen-bond breaking in solution are discussed. PMID:26029818

  16. Density Functionals of Chemical Bonding

    PubMed Central

    Putz, Mihai V.

    2008-01-01

    The behavior of electrons in general many-electronic systems throughout the density functionals of energy is reviewed. The basic physico-chemical concepts of density functional theory are employed to highlight the energy role in chemical structure while its extended influence in electronic localization function helps in chemical bonding understanding. In this context the energy functionals accompanied by electronic localization functions may provide a comprehensive description of the global-local levels electronic structures in general and of chemical bonds in special. Becke-Edgecombe and authors Markovian electronic localization functions are discussed at atomic, molecular and solid state levels. Then, the analytical survey of the main workable kinetic, exchange, and correlation density functionals within local and gradient density approximations is undertaken. The hierarchy of various energy functionals is formulated by employing both the parabolic and statistical correlation degree of them with the electronegativity and chemical hardness indices by means of quantitative structure-property relationship (QSPR) analysis for basic atomic and molecular systems. PMID:19325846

  17. Multifunctional Catalysts to Synthesize and Utilize Energy Carriers

    SciTech Connect

    Lercher, Johannes A.; Appel, Aaron M.; Autrey, Thomas; Bullock, R. Morris; Camaioni, Donald M.; Cho, Herman M.; Dixon, David A.; Dohnalek, Zdenek; Gao, Feng; Glezakou, Vassiliki Alexandra; Henderson, Michael A.; Hu, Jian Z.; Iglesia, Enrique; Karkamkar, Abhijeet J.; Kay, Bruce D.; Kimmel, Gregory A.; Linehan, John C.; Liu, Jun; Lyubinetsky, Igor; Mei, Donghai; Peden, Charles HF; Rousseau, Roger J.; Schenter, Gregory K.; Shaw, Wendy J.; Szanyi, Janos; Wang, Huamin; Wang, Yong; Weber, Robert S.

    2014-06-23

    The central role and critical importance of catalysis in a future based on sustainability, together with the insight that developments have to be knowledge-based have motivated significant efforts to better understand catalyzed processes and to develop new catalytic routes from this knowledge. Overall, three main energy carriers are used worldwide, carbon (and hydrocarbons), hydrogen, and electrons. Conventionally, the stored energy is accessed by oxidizing carbon and hydrogen, forming O-H and C-O bonds and performing work with the produced heat or electricity. Conversely, to synthesize energy carriers sustainably, it is consequently required to reverse the direction, i.e., to break C-O and O-H bonds and form C-C, C-H and H-H bonds. To address these challenges, PNNLs BES-sponsored program comprises three thrust areas with subtasks, focusing on the fundamentals of biomass conversion processes, direct and indirect CO2 reduction, and on elementary studies aimed at generating and using H2. Multi-functionality, i.e., the simultaneous interaction of more than one catalytically active site with the substrate is the key to achieving the atom and energy efficiency in individual steps. The combination of several types of these sites with carefully selected energetics and rate constants is used to generate complex catalysts able to enhance the rates of multistep processes. This short report summarizes recent results obtained in this BES-funded program.

  18. 30 CFR 281.33 - Bonds and bonding requirements.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...Resources 2 2011-07-01 2011-07-01 false Bonds and bonding requirements. 281.33 Section 281.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations 281.33 Bonds and bonding requirements. (a) When the leasing notice...

  19. 30 CFR 281.33 - Bonds and bonding requirements.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...Resources 2 2010-07-01 2010-07-01 false Bonds and bonding requirements. 281.33 Section 281.33 Mineral Resources...CONTINENTAL SHELF Financial Considerations 281.33 Bonds and bonding requirements. (a) When the leasing notice...

  20. Efficient synthesis strategies by application of transition metal-catalyzed carbene/nitrene insertions into C-H bonds.

    PubMed

    Egger, Julian; Carreira, Erick M

    2014-04-01

    Transition metal-catalyzed insertion of carbenes and nitrenes into C-H bonds has become a powerful tool for the construction of C-C and C-N bonds in the synthesis of complex natural products. In this Highlight, a selection of syntheses are detailed involving the implementation of C-H insertion reactions leading to strategies marked by improved efficiency. PMID:24589531