Дисертації: "Attochemistry of chemical bonding"

1

Clarke, D. E. "Bonding in cokes." Thesis, University of Newcastle Upon Tyne, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372550.

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2

Taber, Keith. "Understanding chemical bonding : the development of A level students understanding of the concept of chemical bonding." Thesis, Roehampton University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246174.

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3

Serafin, Lukasz Michal. "Chemical bonding properties in substituted disilynes." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3638.

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The molecular structures of the Si2HX, Si2Li2, SiGeHLi and C2H2 species (where X= H, Li, F and Cl) were studied. All of these species have more than one isomeric form. The critical points on the potential energy surfaces of the Si2HX, Si2Li2and C2H2 species and the minima on the SiGeHLi surface were located. The full six-dimensional potential energy surface (PES) of the Si2Li2 molecule was calculated (for the first time) using the CCSD(T)-F12a/cc-pVTZ-F12 level of theory. The core-valence, zero-point energy and relativistic corrections for the Si2HLi and Si2Li2 species were calculated. Additionally, the electron affinity and Li+ /H+ binding energies for the Si2HLi and Si2Li2 structures were investigated. Furthermore, the anharmonic vibrational-rotational properties for the Si2HLi and Si2Li2 structures were calculated using second-order perturbation theory. The recently developed CCSD(T)-F12a method with the cc-pVTZ-F12 basis set was employed to obtain geometries and relative energies (for the Si2HLi, Si2HF, Si2HCl and Si2Li2 structures) and vibrational frequencies (for the Si2H2 and Si2Li2 structures). The CCSD(T) method with the cc-pVXZ, aug-cc-pVXZ and aug-cc-pV(X+d)Z basis sets, CCSD(T)-F12a/cc-pVXZ (where X=2-4) and the B3LYP/6-311+G(d) levels of theory were also used. Comparison was made of the geometric properties and vibrational frequencies calculated at the different levels of theory. The calculated geometric properties for all the studied species and vibrational frequencies (for the Si2H2 structures) show good agreement with the experimental and theoretical literature. The PES of Si2Li2 was used to perform large scale variational vibrational calculations using the WAVR4 program. The first 2400 totally symmetric energy levels were calculated. The low-lying energy levels were qualitatively correct. Conclusive assignments of the vibrational modes of the Si2Li2 structures were made for the eleven lowest lying energy levels.

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4

Coll, Richard K. "Learners' mental models of chemical bonding." Thesis, Curtin University, 1999. http://hdl.handle.net/20.500.11937/253.

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The research reported in this thesis comprised a cross-age inquiry of learners' mental models for chemical bonding. Learners were chosen purposefully from three academic levels-senior secondary school (Year-13, age range 17-18 years old), undergraduate (age range 19-21 years), and postgraduate (comprising MSc and PhD; age range 22- 27 years). The principal research goal was to establish learners' preferred mental models for the concept of chemical bonding. Other research goals were to establish if and how learners made use of analogy to understand chemical bonding and to establish the prevalence of learners' alternative conceptions for chemical bonding. The research inquiry was conducted from within a constructivist paradigm; specifically the researcher ascribed to a social and contextual constructivist belief system.Based on a review of the science education literature a decision was made to classify mental models into four classes according to the typology of Norman (1983), namely, the target system, a conceptual model, the users' or learners' mental model and the scientists' conceptualisation. A conceptual theme for the inquiry was developed based on this typology resulting in the identification of target systems-metallic, ionic and covalent bonding. Subsequently, target models for each of the three target systems were identified, namely, the sea of electrons model and the band theory for metallic bonding; the electrostatic model, and the theoretical electrostatic model for ionic bonding; and the octet rule, the valence bond approach, the molecular orbital theory and the ligand field theory for covalent bonding. A conceptual model, consisting of a summary of the salient points of the target models, was developed by the researcher. Once validated by four of the instructors involved in the inquiry, this formed the scientists' conceptualisation for the target models.Learners' mental models were elicited by the use of a three phase semi-structured interview protocol for each of the three target systems based on the translation interface developed by Johnson and Gott (1996). The protocol consisted of showing participants samples of common substances and asking them to describe the bonding in these materials. In addition, participants were shown Interviews About Events (IAE), focus cards which depicted events involving chemical bonding or contained depicted models of bonding for the three target systems. Transcriptions of audio-tapes combined with diagrams produced by the participants formed the data corpus for the inquiry. Learners' mental models were compiled into inventories for each of the target systems. Examination of inventories enabled identification of commonality of views which were validated by four instructors-two instructors from the teaching institutions involved in the inquiry, and two instructors independent of the inquiry.The research reported in this thesis revealed that learners across all three academic levels preferred simple or realist mental models for chemical bonding, such as the sea of electrons model and the octet rule. Learners frequently used concepts from other more sophisticated models to aid their explanations when their preferred mental models were found to be inadequate. Senior level learners were more critical of mental models, particularly depicted models provided on IAE focus cards. Furthermore, senior level learners were able to describe their mental models in greater detail than their younger counterparts. However, the inquiry found considerable commonality across all three levels of learner, suggesting mental models are relatively stable.Learners' use of analogy was classified according to Dagher's (1995a) typology, namely, simple, narrative, peripheral and compound. Learners' use of analogy for the understanding of chemical bonding was found to be idiosyncratic. When they struggled to explain aspects of their mental models for chemical bonding, learners made extensive use of simple analogy, that typically involved the mapping of a single attribute between the target and source domains. There did not appear to be any correlation between academic ability or academic level and use of analogy. However, learners made greater use of compound analogy for the target systems of metallic and ionic bonding, mostly as a result of the use of analogical models during instruction.This inquiry revealed prevalent alternative conceptions for chemical bonding across all three academic levels of learner. This is a somewhat surprising result considering that the mental models preferred by learners were typically simple, realist models they had encountered during instruction. Learners' alternative conceptions often concerned simple conceptions such as ionic size, the presence of charged species in non- polar molecular compounds, and misunderstandings about the strength of bonding in metals and ionic substances. The inquiry also revealed widespread confusion about intermolecular and intramolecular bonding, and the nature of lattices structures for ionic and metallic substances.The inquiry resulted in a number of recommendations. It is proposed that it may be more beneficial to teach less content at the introductory level, that is, delivering a curriculum that is more appropriate for non-specialist chemistry majors. Hence, one recommendation is for instructors to examine the intended curriculum carefully and be more critical regarding the value of inclusion of some course content. A second recommendation is that sophisticated models of chemical bonding are better taught only at advanced stages of the degree program, and that teaching from a contructivist view of learning may be beneficial. The third recommendation relates to the fact that learners spontaneously generated analogies to aid their explanations and conceptual understanding, consequently, learners may benefit from greater use of analogy during instruction.

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5

Coll, Richard K. "Learners' mental models of chemical bonding." Curtin University of Technology, Science and Mathematics Education Centre, 1999. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=10124.

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The research reported in this thesis comprised a cross-age inquiry of learners' mental models for chemical bonding. Learners were chosen purposefully from three academic levels-senior secondary school (Year-13, age range 17-18 years old), undergraduate (age range 19-21 years), and postgraduate (comprising MSc and PhD; age range 22- 27 years). The principal research goal was to establish learners' preferred mental models for the concept of chemical bonding. Other research goals were to establish if and how learners made use of analogy to understand chemical bonding and to establish the prevalence of learners' alternative conceptions for chemical bonding. The research inquiry was conducted from within a constructivist paradigm; specifically the researcher ascribed to a social and contextual constructivist belief system.Based on a review of the science education literature a decision was made to classify mental models into four classes according to the typology of Norman (1983), namely, the target system, a conceptual model, the users' or learners' mental model and the scientists' conceptualisation. A conceptual theme for the inquiry was developed based on this typology resulting in the identification of target systems-metallic, ionic and covalent bonding. Subsequently, target models for each of the three target systems were identified, namely, the sea of electrons model and the band theory for metallic bonding; the electrostatic model, and the theoretical electrostatic model for ionic bonding; and the octet rule, the valence bond approach, the molecular orbital theory and the ligand field theory for covalent bonding. A conceptual model, consisting of a summary of the salient points of the target models, was developed by the researcher. Once validated by four of the instructors involved in the inquiry, this formed the scientists' conceptualisation for the target ++
models.Learners' mental models were elicited by the use of a three phase semi-structured interview protocol for each of the three target systems based on the translation interface developed by Johnson and Gott (1996). The protocol consisted of showing participants samples of common substances and asking them to describe the bonding in these materials. In addition, participants were shown Interviews About Events (IAE), focus cards which depicted events involving chemical bonding or contained depicted models of bonding for the three target systems. Transcriptions of audio-tapes combined with diagrams produced by the participants formed the data corpus for the inquiry. Learners' mental models were compiled into inventories for each of the target systems. Examination of inventories enabled identification of commonality of views which were validated by four instructors-two instructors from the teaching institutions involved in the inquiry, and two instructors independent of the inquiry.The research reported in this thesis revealed that learners across all three academic levels preferred simple or realist mental models for chemical bonding, such as the sea of electrons model and the octet rule. Learners frequently used concepts from other more sophisticated models to aid their explanations when their preferred mental models were found to be inadequate. Senior level learners were more critical of mental models, particularly depicted models provided on IAE focus cards. Furthermore, senior level learners were able to describe their mental models in greater detail than their younger counterparts. However, the inquiry found considerable commonality across all three levels of learner, suggesting mental models are relatively stable.Learners' use of analogy was classified according to Dagher's (1995a) typology, namely, simple, narrative, peripheral and compound. Learners' use of ++
analogy for the understanding of chemical bonding was found to be idiosyncratic. When they struggled to explain aspects of their mental models for chemical bonding, learners made extensive use of simple analogy, that typically involved the mapping of a single attribute between the target and source domains. There did not appear to be any correlation between academic ability or academic level and use of analogy. However, learners made greater use of compound analogy for the target systems of metallic and ionic bonding, mostly as a result of the use of analogical models during instruction.This inquiry revealed prevalent alternative conceptions for chemical bonding across all three academic levels of learner. This is a somewhat surprising result considering that the mental models preferred by learners were typically simple, realist models they had encountered during instruction. Learners' alternative conceptions often concerned simple conceptions such as ionic size, the presence of charged species in non- polar molecular compounds, and misunderstandings about the strength of bonding in metals and ionic substances. The inquiry also revealed widespread confusion about intermolecular and intramolecular bonding, and the nature of lattices structures for ionic and metallic substances.The inquiry resulted in a number of recommendations. It is proposed that it may be more beneficial to teach less content at the introductory level, that is, delivering a curriculum that is more appropriate for non-specialist chemistry majors. Hence, one recommendation is for instructors to examine the intended curriculum carefully and be more critical regarding the value of inclusion of some course content. A second recommendation is that sophisticated models of chemical bonding are better taught only at advanced stages of the degree program, and that teaching from a contructivist view of ++
learning may be beneficial. The third recommendation relates to the fact that learners spontaneously generated analogies to aid their explanations and conceptual understanding, consequently, learners may benefit from greater use of analogy during instruction.

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6

Öström, Henrik. "Chemical Bonding of Hydrocarbons to Metal Surfaces." Doctoral thesis, Stockholm University, Department of Physics, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-171.

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Using x-ray absorption spectroscopy (XAS), x-ray emission spectroscopy (XES) and x-ray photoelectron spectroscopy (XPS) in combination with density functional theory (DFT) the changes in electronic and geometric structure of hydrocarbons upon adsorption are determined. The chemical bonding is analyzed and the results provide new insights in the mechanisms responsible for dehydrogenation in heterogeneous catalysis.

In the case of alkanes, n-octane and methane are studied. XAS and XES show significant changes in the electronic structure upon adsorption. XES shows new adsorption induced occupied states and XAS shows quenching of CH*/Rydberg states in n-octane. In methane the symmetry forbidden gas phase lowest unoccupied molecular orbital becomes allowed due to broken symmetry. New adsorption induced unoccupied features with mainly metal character appear just above the Fermi level in XA spectra of both adsorbed methane and n-octane. These changes are not observed in DFT total energy geometry optimizations. Comparison between experimental and computed spectra for different adsorbate geometries reveals that the molecular structures are significantly changed in both molecules. The C-C bonds in n-octane are shortened upon adsorption and the C-H bonds are elongated in both n-octane and methane.

In addition ethylene and acetylene are studied as model systems for unsaturated hydrocarbons. The validity of both the Dewar-Chatt-Duncanson chemisorption model and the alternative spin-uncoupling picture is confirmed, as well as C-C bond elongation and upward bending of the C-H bonds.

The bonding of ethylene to Cu(110) and Ni(110) are compared and the results show that the main difference is the amount of back-donation into the molecular π* orbital, which allows the molecule to desorb molecularly from the Cu(110) surface, whereas it is dehydrogenated upon heating on the Ni(110) surface.

Acetylene is found to adsorb in two different adsorption sites on the Cu(110) surface at liquid nitrogen temperature. Upon heating the molecules move into one of these sites due to attractive adsorbate-adsorbate interaction and only one adsorbed species is present at room temperature, at which point the molecules start reacting to form benzene. The bonding of the two species is very similar in both sites and the carbon atoms are rehybridized essentially to sp².

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7

Öström, Henrik. "Chemical bonding of hydrocarbons to metal surfaces /." Stockholm : Fysikum, Univ, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-171.

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8

Akram, Mohammed. "Bonding mechanism in a new refractory castable." Thesis, Aston University, 1996. http://publications.aston.ac.uk/9647/.

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9

Popov, Ivan A. "Chemical Bonding in Novel 0-, 1-, 2-, and 3-Dimensional Chemical Species." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/5883.

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While the trial and error approach is still being a dominant pathway for synthesis of various compounds in chemistry, computation-driven approaches have recently been shown to be a very efficient way towards the rational design of new materials with tailored properties. In principle, theoretical design of materials may not only significantly reduce the costs associated with the experiment, but may also result in the prediction of novel compounds possessing completely unexpected geometries. These compounds can serve as long-lived catalysts, powerful batteries, efficient solar cells, or reliable energy storage materials. Since geometric structure of any system is related to its electronic structure, it is very important to understand how atoms are bonded together since the chemical properties of materials depend upon the chemical bonds that make it up. Armed with this knowledge, researchers are able to develop theoretical models and design principles, which can be used to describe the geometry of the given system as well as rationally design novel species possessing desired structures and properties. The common thread of this dissertation was the development of the chemical bonding models for a vast range of chemical systems, including gas-phase clusters observed in a molecular beam or isolated in a condensed phase, various hypervalent iodine molecules, experimentally made two-dimensional materials of carbon and boron, as well as theoretically predicted molecular chains and atom-thin sheets awaiting their experimental confirmation.

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10

Öberg, Henrik. "Surface reactions and chemical bonding in heterogeneous catalysis." Doctoral thesis, Stockholms universitet, Fysikum, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-102323.

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This thesis summarizes studies which focus on addressing, using both theoretical and experimental methods, fundamental questions about surface phenomena, such as chemical reactions and bonding, related to processes in heterogeneous catalysis. The main focus is on the theoretical approach and this aspect of the results. The included articles are collected into three categories of which the first contains detailed studies of model systems in heterogeneous catalysis. For example, the trimerization of acetylene adsorbed on Cu(110) is measured using vibrational spectroscopy and modeled within the framework of Density Functional Theory (DFT) and quantitative agreement of the reaction barriers is obtained. In the second category, aspects of fuel cell catalysis are discussed. O2 dissociation is rate-limiting for the reduction of oxygen (ORR) under certain conditions and we find that adsorbate-adsorbate interactions are decisive when modeling this reaction step. Oxidation of Pt(111) (Pt is the electrocatalyst), which may alter the overall activity of the catalyst, is found to start via a PtO-like surface oxide while formation of α-PtO2 trilayers precedes bulk oxidation. When considering alternative catalyst materials for the ORR, their stability needs to be investigated in detail under realistic conditions. The Pt/Cu(111) skin alloy offers a promising candidate but segregation of Cu atoms to the surface is induced by O adsorption. This is confirmed by modeling oxygen x-ray emission (XES) and absorption spectra of the segregated system and near-perfect agreement with experiment is obtained when vibrational interference effects are included in the computed XES. The last category shows results from femtosecond laser measurements of processes involving CO on Ru(0001). Using free-electron x-ray laser experiments a precursor state to desorption is detected and also found in simulations if van der Waals effects are included. Resonant XES can be used to distinguish two different species of CO on the surface; vibrationally hot, chemisorbed CO and CO in the precursor state. Laser-induced CO oxidation on Ru(0001) is modeled and three competing mechanisms are found. Kinetic modeling reproduces the experiment qualitatively.

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 8: Manuscript.

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11

Baranov, Alexey. "Chemical Bonding Analysis of Solids in Position Space." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-180813.

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Modern solid state chemistry is inconceivable without theoretical treatment of solids thanks to the availability of efficient and accurate computational methods. Being developed mainly by physicist's community and deeply rooted in the formalism of reciprocal space, they often lack connections to familiar chemical concepts, indispensable for the chemical understanding of matter. Quantum chemical topology approach is a powerful theory able to efficiently recover chemical entities from the abstract description of a system given by its density matrices. It can be used to partition any many-electron system into the atoms, using the topology of electron density or for instance into atomic shells, using the topology of ELI-D field. Various characteristics of interactions between these chemical building blocks can be obtained applying bonding indicators, e.g. from the analysis of domain-averaged properties. Quantum chemical topology methods have been extended in the current work for the applications on the diversity of theoretical methods widely used for the description of solids nowadays – from the mean field Kohn-Sham density functional theory to the reduced one-electron density matrices functional theory or from the scalar-relativistic methods to the many-component formalisms employing spinor wavefunctions. It has been shown, that they provide chemically meaningful description of the bonding which is universally applicable to any class of extended systems, be it ionic insulator, covalent solid or metal. It has been shown, that the relativistic effects on the chemical bonding can be easily revealed using extensions of bonding indicators developed in the current work. Classical chemical concepts like Zintl-Klemm concept can be easily recovered with these descriptions. Intimate connection between the class of the material and the degree of chemical bonding delocalization has been also established. All these methods have been successfully applied to the various classes of solids and delivered novel insights on their crystal structure, properties, solid state transitions and reactivity.

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12

Willis, Joshua Jerome. "27th Immunoglobulin Domain: Fold Catastrophes and Hydrogen Bonding." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1332855603.

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13

Joshua, Nilmini Sureka. "Novel phosphate bonding composites /." View thesis, 1997. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030828.115030/index.html.

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14

Grechnyev, Oleksiy. "Theoretical Studies of Two-Dimensional Magnetism and Chemical Bonding." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4815.

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15

Shaw, Lindsey Ann. "The development of chemical bonding systems for refractories/ceramics." Thesis, Keele University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341290.

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16

Kim, Yang-Soo. "Electronic Structure and Chemical Bonding of Transition Metal Dichalcogenides." Kyoto University, 1999. http://hdl.handle.net/2433/181809.

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17

Macedo, Georgia Valente de Yamauchi Mitsuo. "Effect of chemical cross-linking agents on dentin bonding." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2008. http://dc.lib.unc.edu/u?/etd,1756.

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Thesis (M.S.)--University of North Carolina at Chapel Hill, 2008.
Title from electronic title page (viewed Sep. 16, 2008). "... in partial fulfillment of the requirements for the degree of Master of Science in the Department of Operative Dentistry - School of Dentistry." Discipline: Operative Dentistry; Department/School: Dentistry.

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18

Joshua, Nilmini Sureka, University of Western Sydney, and Faculty of Science and Technology. "Novel phosphate bonding composites." THESIS_FST_XXX_Joshua_N.xml, 1997. http://handle.uws.edu.au:8081/1959.7/282.

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A cement material has been developed that has a controllable set time, compressive strength of about 50 MPa and shrinkage of under 2% when heated to 960 degrees centigrade. The main compound of this material has been shown to be the potassium analogue of struvite, in which potassium ion is substituted for the ammonium ion. The cement is formed by reacting a slurry made with potassium carbonate and monoammonium phosphate with magnesium oxide. Ihe amount and rate of addition of water to the mixture is controlled to determine the set time. It has been demonstrated that this cement may be used as a matrix in conjunction with cenospheres or cellulose fibres to form a low density composite material, and with silica powder to form a high strength composite. As well as optimising the cement mix for maximum strength and minimum shrinkage, a variety of properties of the K-cement were investigated. It was found that long term exposure of the cement to the atmosphere does not result in the formation of magnesium carbonate, but long term exposure to saline solutions can result in the formation of dypingite on the surface. No effect on strength was observed as a consequence of the age of the slurry or the cement, within 1-2 weeks
Doctor of Philosophy (PhD)

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19

Bende, David. "Chemical Bonding Models and Their Implications for Bonding-Property Relations in MgAgAs-Type and Related Compounds." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-201406.

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In this work, chemical bonding models are developed and extended by the aid of the quantum-chemical position-space analysis. The chemical bonding models are then utilized to rationalize and predict the structure and conducting properties of MgAgAs-type and other intermetallic compounds. Additionally, new position-space bonding indicators are developed.

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20

Emseis, Paul, University of Western Sydney, of Science Technology and Environment College, and of Science Food and Horticulture School. "Non-classical bonding in chiral metal complexes." THESIS_CSTE_SFH_Emseis_P.xml, 2003. http://handle.uws.edu.au:8081/1959.7/557.

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Intramolecular non-covalent interactions between aromatic ligands in chiral Ru(II) and Co(III) complexes have been investigated in this study. Several investigations were carried out and findings given. The results of the study, which demonstrate the significance of non-covalent interactions involving aromatic residues to the determination of the molecular conformation, serve to highlight the suitability of simple chiral metal complexes to act as models for interactions
Doctor of Philosophy (PhD)

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21

Feixas, Geronès Ferran. "Analysis of chemical bonding and aromaticity from electronic delocalization descriptors." Doctoral thesis, Universitat de Girona, 2011. http://hdl.handle.net/10803/37471.

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Interactions between electrons determine the structure and properties of matter from molecules to solids. Therefore, the understanding of the electronic structure of molecules will enable us to extract relevant chemical information. In the first part of this thesis, we focus our attention on the analysis of chemical bonding by means of the Electron Localization Function (ELF) and the Domain-Averaged Fermi Hole analysis (DAFH). In the second part, we assess the performance of some indicators of aromaticity by analyzing their advantages and drawbacks. We propose a series of tests based on well-known aromaticity trends that can be applied to evaluate the aromaticity of current and future indicators of aromaticity in both organic and inorganic species. Moreover, we investigate the nature of electron delocalization in both aromatic and antiaromatic systems in the light of Hückel’s (4n + 2) rule. Finally, we analyze the phenomenon of multiple aromaticity in all-metal clusters.
Les interaccions entre electrons determinen l’estructura i propietats de la matèria. Per tant, la comprensió de l’estructura electrònica de les molècules ens permetrà extreure informació química rellevant. En la primera part d’aquesta tesi, centrem la nostra atenció en l’anàlisi de l’enllaç químic per mitjà de la funció de localització electrònica (ELF) i l’anàlisi dels anomenats domain averaged Fermi holes (DAFH). En la segona part, s’avalua el comportament d’alguns indicadors d’aromaticitat analitzant els seus avantatges i inconvenients. Al llarg d’aquesta part, es proposen una sèrie de tests basats en tendències d’aromaticitat conegudes que es poden aplicar per avaluar el comportament dels indicadors actuals en espècies tan orgàniques com inorgàniques. A més a més, s’investiga la naturalesa de la deslocalització d’electrons en sistemes aromàtics i antiaromàtics que segueixen la regla 4n+2 que proposà Hückel. Finalment, analitzem el fenomen de l’aromaticitat múltiple en sistemes metàl•lics

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22

Jürgensen, Astrid. "Probing electronic structure and chemical bonding with x-ray spectroscopy." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0034/NQ46862.pdf.

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23

Gammon, W. Jason. "Chemical bonding in hard and elastic amorphous carbon-nitride films." W&M ScholarWorks, 2003. https://scholarworks.wm.edu/etd/1539623423.

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In this study, the chemical bonding in hard and elastic amorphous carbon nitride (a-CNx) films is investigated with x-ray photoelectron spectroscopy (XPS) and 15N, 13C, and 1H nuclear magnetic resonance (NMR) spectroscopy. The films were deposited by DC Magnetron sputtering in a pure nitrogen discharge on Si(001) substrates at 300--400??C. Nanoindentation measurements reveal an elastic modulus of ∼50 GPa and a hardness of ∼5 GPa, thus confirming our films are highly elastic but resist plastic deformation.;Our 13C NMR study demonstrates the absence of sp 3-bonded carbon in this material. Collectively, our N(1s) XPS, 13C NMR, and 15N NMR data suggest a film-bonding model that has an aromatic carbon structure with sp2-hybridized nitrogen incorporated in heterocyclic rings. We demonstrate that the nitrogen bonding is predominantly in configurations similar to those in pyridine and pyrrole. In addition, the data indicate that the a-CNx films prepared for this study have low hydrogen content, but are hydrophilic. Specifically, results from 15N and 13C cross polarization (CP) and 1H magic angle spinning (MAS) NMR experiments suggest that nitrogen sites are susceptible to protonation from water absorbed during sample preparation for the NMR experiments. The sensitivity of the surface of a-CNx to water absorption may impact tribological applications for this material.;In accord with our XPS and NMR spectroscopic studies on a-CN x films, we propose a film-structure model consisting of buckled graphitic planes that are cross-linked together by sp2 hybridized carbons. The curvature and cross-linking is attributed to a type of compound defect, which is formed by placing a pentagon next to single-atom vacancy in a graphite layer. Our proposed film structure is called the pentagon-with-vacancy-defect (5VD) model. Using Hartree-Fock calculations, we show that the 5VD, film-structure model is compatible with our XPS, NMR, and nanoindentation measurements and with previous transmission electron microscopy (TEM) and computational work.

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24

RACIOPPI, STEFANO. "CHEMICAL BONDING IN METAL-ORGANIC SYSTEMS: NATURE, STRUCTURES AND PROPERTIES." Doctoral thesis, Università degli Studi di Milano, 2019. http://hdl.handle.net/2434/606271.

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The main purpose of my thesis is the application of theoretical and experimental methods for the study of the nature of the chemical bond and its effect on structures and properties in organome-tallic systems, like Metal Carbonyl Clusters and Coordination Polymers (CPs) featuring, in some of the cases under study, intrinsic porosity (in the following, PCP for Porous Coordination Polymers or MOFs for Metal-Organic Frameworks). Concerning metal clusters, we worked on high nuclearity metal carbonyl clusters, and, particularly, on those featuring semi-interstitial atoms. The chemical bonding and the related properties in these peculiar class of molecules are still a matter of discussion in the scientific community. Concerning the class of Metal-organic Frameworks, we focused our attention on azolate-based ligands as building blocks for the synthesis of MOFs, looking at their possible future application as ultra-low dielectric constant materials in electronic devices. Finally, we investigated the structural behavior of Coordination Polymers at non-ambient condition (high pressure, in the order of 0-8 GPa), to induce new interactions and attitudes like electric conductivity. This research required the application of a bunch of theoretical tools, assisted by accurate single crystal X-ray diffraction experiments in standard and not-standard conditions (low temperature and high pressure). Moreover, a protocol for comparing different energy decomposition methods was developed and successfully applied to investigate the bonding nature in simple and complex systems.

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25

Emseis, Paul. "Non-classical bonding in chiral metal complexes." Thesis, View thesis, 2003. http://handle.uws.edu.au:8081/1959.7/557.

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Intramolecular non-covalent interactions between aromatic ligands in chiral Ru(II) and Co(III) complexes have been investigated in this study. Several investigations were carried out and findings given. The results of the study, which demonstrate the significance of non-covalent interactions involving aromatic residues to the determination of the molecular conformation, serve to highlight the suitability of simple chiral metal complexes to act as models for interactions

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26

Flint, Bruce W. "Exploring the bonding and reaction chemistry of gold and platinum complexes /." free to MU campus, to others for purchase, 2001. http://wwwlib.umi.com/cr/mo/fullcit?p3036824.

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27

Callahan, John J. "Optoelectronic hybrid integration utilizing Au/Sn bonding." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/15461.

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28

Emseis, Paul. "Non-classical bonding in chiral metal complexes /." View thesis, 2003. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20031007.121552/index.html.

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Анотація:

Thesis (Ph.D.) -- University of Western Sydney, 2003.
"A thesis submitted as a requirement for admission to the degree of Doctor of Philosophy" Includes bibliographical references (leaves vi, 194-200).

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29

Bishop, Sarah R. "Chemical dynamics and bonding at gas/semiconductor and oxide/semiconductor interfaces." Diss., [La Jolla] : University of California, San Diego, 2010. http://wwwlib.umi.com/cr/ucsd/fullcit?p3397565.

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Thesis (Ph. D.)--University of California, San Diego, 2010.
Title from first page of PDF file (viewed April 7, 2010). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.

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30

Bristow, Jessica K. "Chemical bonding in metal-organic frameworks : from fundamentals to design principles." Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.698964.

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Society is now dependent on the continued development and access to modern technology. Materials science therefore stands at the forefront of resolving and tuning functional materials properties, and designing technologies to improve our health, economy and environment. The content of this thesis covers a wide range of methods and approaches for understanding the chemical complexities, and tuneable properties of a unique subset of materials named metal-organic frameworks. The number of available precursor components for synthesising MOFs has led to a plethora of possible final crystal structures, with vast differences in observed material properties. The use of computational approaches in the prediction of potential functional frameworks, and also for resolving the origin behind observed phenomena, is essential for directing further work in the field. Work in this thesis includes the parameterisation of an approach that would allow a large-scale and cheap screening procedure of the thermodynamic properties of MOFs. Other work in this thesis includes the calculation of defective framework structures and the thermodynamics associated with their formation. Defects that occur in MOFs, when compared to inorganic binary materials such as oxides, can be considered as severe and non-dilute. The concentration and distribution of potential defects and the stability of the framework as a function of these factors, is a poorly understood area in the research field of MOFs. Finally, interfacing MOFs with surfaces is a relatively new approach for designing functional devices for applications such as gas absorption and photovoltaics. In this thesis we calculate interface binding sites and energetics of adhesion of an archetypal example of a MOF interfacing a metal oxide. Each approach and direction taken in the work forming this thesis were taken to resolve the theory behind observed phenomena in experiments, and to provide a platform for investigating the potential material properties of yet unsynthesised MOFs.

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31

Jang, Nak Han. "Developing and validating a chemical bonding instrument for Korean high school students /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p3115557.

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32

Zhou, Yonghui. "Interface optimisation and bonding mechanism of rubber-wood-plastic composites." Thesis, Brunel University, 2018. http://bura.brunel.ac.uk/handle/2438/16095.

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The incorporation of waste tyre rubber into thermoplastics to develop a class of polymer composites with both elastomeric and thermoplastic behaviour has gained a lot of attention and is becoming one of the most straightforward and preferred options to achieve the valorisation of waste tyres. In view of the unique properties rubber possesses and the rapid expansion and versatile application of wood plastic composites (WPC) materials, the inclusion of tyre rubber as raw material into WPC to develop an entirely new generation of WPC, namely rubber-wood-plastic composites (RubWPC), was presumed to be another highly promising solution to turn waste tyres into value-added materials. This research starts with the interfacial optimisation of Rubber-PE composites and WPC by the use of maleated and silane coupling agents, aiming at addressing their poor constituent compatibility and interfacial bonding, thus enabling the optimal design of RubWPC. Chemical, physical and mechanical bonding scenarios of both untreated and treated composites were revealed by conducting ATR-FTIR, NMR, SEM and FM analyses. The contribution of the optimised interface to the bulk mechanical property of the composites were assessed by carrying out DMA and tensile property analysis. The influence of the coupling agent treatments on the in situ mechanical property of WPC was first determined by nanoindentation analysis, which led to a thorough understanding of the interfacial characteristics and the correlation between in situ and bulk mechanical properties. This research focuses on the novel formulation of RubWPC and the understanding of bonding mechanism. Chemical bonding and interface structure studies revealed that interdiffusion, molecular attractions, chemical reactions, and mechanical interlocking were mutually responsible for the enhancement of the interfacial adhesion and bonding of the coupling agent treated RubWPC. The improved interface gave rise to the increase of bulk mechanical properties, while the continuous addition of rubber particle exerted an opposite influence on the property of RubWPC. The composite with optimised interface possessed superior nanomechanical properties due to the resin penetration into cell lumens and vessels and the reaction between cell walls and coupling agents.

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33

Lee, Wai-shing, and 李威成. "An evaluation on the teaching and learning of chemical bonding and structure." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B50176845.

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The problematics of the teaching and learning of chemical bonding has been widely reported in the literature. Following this, Taber (2001) proposed a teaching sequence alternative to those available in existing curriculum documents and textbooks. He proposed that teaching be started from metallic structure to ionic structure, then giant covalent structure and finally simple molecular structure. During teaching, teachers should be cautioned about the use of language, the undue emphasis on the role of atoms (atomic ontology), the explication of the nature of bonding (based on electrostatic forces rather than electron transfer or sharing), and a better integration of the relationship between bonding and structure. In relation to the literature about scientific modelling, bonding should be taught as an ‘explanation’ of properties of chemicals, rather than a mere ‘description’ of structure. This paper reports an empirical study of a class of Year 10 students’ learning outcomes based on the proposed teaching sequence and emphases. Throughout the learning of the topic ‘chemical bonding’ which spanned two months, three students ranged from the highest to medium achieving students in the class were selected for interviews. Each student was interviewed on four separate occasions in the course of their learning of ‘chemical bonding’. Their understanding of concepts in relation to chemical bonding was probed through their verbal and visual representations. The effectiveness of the teaching sequence was evaluated in the light the alternative conceptions reported in the literature, strategy and suggestions for further improvements were discussed.
published_or_final_version
Education
Master
Master of Education

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34

Mountain, A. R. E. "Quantum chemical modelling of organo transition metal structure, bonding, and reaction mechanism." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/1559959/.

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In this thesis, density functional theory is used to investigate the structure, bonding, and reaction mechanisms of two families of organometallic compounds discussed below. The first chapter briefly introduces the research projects undertaken for this PhD, while the second introduces the theoretical background of electronic structure calculations. Chapter 3 begins with an introduction to homogenous Ziegler-Natta catalysis of olefin polymerisation, with a focus on chain propagation and termination reaction mechanisms for propylene homopolymerisation. These mechanisms are then explored in benchmarking studies of the naked cationic post-metallocene catalyst [MeTiCp*{CN(Ph)N(iPr)2}]+, comparing reaction profiles calculated using different approaches to describe dispersion and solvent effects, as well as those found using ab initio methods. It is concluded that dispersion interactions play an important role in predicting the expected trends in reaction barrier height for propagation vs. termination, and the methodology which best describes this is chosen and implemented in the subsequent chapter. The effects of the anionic co-catalyst [B(C6F5)4] on homopolymerisation studies of ethylene and propylene with [MeTiCp*{CN(Ph)N(iPr)2}]+, are explored in Chapter 4. Differences between olefin complexation, chain propagation and termination reactions calculated with and without the anion are discussed, as well as predictions of macroscopic properties of polymers produced using this catalytic system. Chapter 5 introduces a different research project; the investigation of the structure, bonding, and reactivity of metal boryl and gallyl compounds, Ln{E(NArCH)2}{Me3SiCH2C(NCy)2}2(THF)n (Ln = Sc, Y, Lu; E = B, Ga; n = 0, 1). The changes in structure and Ln–E bonding interaction are compared between five- and six-coordinate analogues of the systems, accounting for the difference in coordination number of the boryls vs. the gallyls, and their reactivity with carbodiimide iPrNCNiPr. Finally, the mechanism for carbodiimide insertion into the Mg–Ga bond of Mg{'iPPNacNac}Ga(NDippCH)2} systems is explored.

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35

Hogan, Simon William Leslie. "The role of halogen bonding in biomolecules." Thesis, University of St Andrews, 2018. http://hdl.handle.net/10023/13840.

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This study concerns halogen bonding between small molecules. Except where otherwise stated herein this investigation was performed exclusively using the M06-2X density functional, in conjunction with the 6-31+G* basis set except for iodine and astatine which were treated using the aug-cc-pVDZ-PP basis set with relativistic pseudopotentials. All calculations were performed in the gas phase. The counterpoise procedure was employed for all full geometry optimisations. Statistical analysis of the Cambridge Structural Database, wherein the frequency of structures as a function of halogen bond angle and distance constituted the sole part of this study not to be based on density functional theory. Except in chapter 5, all halogens from fluorine to astatine are investigated. In chapter 3, halogen bonding between halobenzene and a single water molecule is discussed. Competition between R – X•••OH2 halogen bonding and R – X•••H-O-H hydrogen bonding interactions is described. This system is analogous to the more elaborate microsolvated 1- methyl-5-halouracil system described in chapter 4. In this latter system one 1-methyl-5- halouracil molecule interacts with either one or two water molecules. A central feature of the investigation into this system is competition between R – X•••OH2 and R=O•••H-O-H hydrogen bonding. In chapter 5, halogen bonding is discussed in the context of the thyroid system. In particular halogen bonding between a thyroxine iodine atom and the protein backbone as well as crystal water molecules is the subject of this chapter. The effect of substitution of the iodine atom with an astatine atom is presented. Chapter 6 is concerned with halogen bonding in halogenated DNA base pairs. Interaction energies are compared with those of the canonical base pairs, and the effect of halogen bonding on geometry is also discussed. For each system, halogen bonding was found to become stronger and more tolerant of non- linear bond angles going down the halogen group.

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36

Janin, Emmanuelle. "Adsorption and bonding on platinum : influence of the surface structure and chemical composition." Doctoral thesis, KTH, Physics, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3079.

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This thesis deals with the influence of the structure andchemical composition of platinum surfaces on the adsorption ofsome molecules. Three main lines can be distinguished : 1) thecharacterisation of clean/modified surfaces, 2) the adsorptionof some simple atoms and molecules on these surfaces andfinally 3) the adsorption of 2-butenal, a bi-functionalmolecule containing a C=C group conjugated with a C=O group.The main tools used in this work are scanning tunnellingmicroscopy, photoelectron spectroscopy and high-resolutionelectron energy loss spectroscopy, in combination with quantumchemical calculations.

The platinum (111)(1× 1) and (110)(1× 2) surfacesare chosen as substrates. Pt(111) is a non-reconstructedclose-packed surface, while the Pt(110) surface is open, due toits missing row (MR) reconstruction, which results in thealternation of ridges, {111} microfacets and valleys. Titaniumgrows on Pt(111) in a Volmer-Weber mode. Pronounced reactionsbetween Pt and Ti are detected already at room temperature asthe Ti2p and Pt4f_7/2core-level shifts are characteristic of the Pt₃Ti alloy. Carbon segregated on the (110) surfaceappears as extended graphitic regions, which smoothen thesubstrate. Sn deposition at room temperature on Pt(110) resultsin the appearance of small islands, randomly spread over thesurface. The presence of mobile Sn ad-atoms and Pt-Sn-Ptalloyed chains in the valley of the MR reconstruction is alsoevidenced. Annealing the surface results in the rearrangementof the tin in the surface layer, together with a globalshortening of the terraces in the [110]direction and anincreased density of (1× n) (n>2) defects.

The adsorption of atomic hydrogen and oxygen has beenperformed on the Pt(111)( √ 3x √3)R30º surfacealloy and on Pt(110)(1× 2) respectively. The adsorptionsite of these atoms is changed as compared to the onedetermined on the clean Pt(111) surface (i.e. fcc hollow site): H is adsorbed on-top site on the (√3× √3)surface alloy, and O sits on the ridge of the missing rowreconstruction in bridge site. Carbon monoxide adsorption wasperformed on Pt(111) and Pt(110)(1× 2) surfaces, modifiedor not by tin. On the unmodified (111) surface, CO adsorbsfirst in top site, thenin bridge. Changing the geometry of thesurface to the (110) results in the vanishing of the bridgesite population. Modifying these surfaces by Sn does not changethe CO adsorption site.

Finally, 2-butenal (CH₃-CH=CH-CH=O) has been adsorbed at 100 K on thePt(111) surface and the Sn/Pt(111) surface alloys. On theunmodified Pt surface, comparison with results obtained forpropene (CH₂=CH-CH₃) adsorption evidences the involvement of the C=Cgroup of the 2-butenal molecule in the bonding to the Ptsurface. The carbonyl group is also suggested to take part inthe bonding, through a σ_ccη₁(O) configuration. This carbonyl group bondingdisappears when Sn is alloyed to the surface, and the formationof a new physisorbed phase is detected.

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37

Stoltzfus, Matthew W. "Structure-property relationships in solid state materials a computational approach emphasizing chemical bonding /." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1190087366.

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38

Mizuno, Masataka. "Theoretical Study on Chemical Bonding around Lattice Imperfections in 3d-Transition Metal Compounds." Kyoto University, 1997. http://hdl.handle.net/2433/160826.

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本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものである
Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第6864号
工博第1615号
新制||工||1068(附属図書館)
UT51-97-H248
京都大学大学院工学研究科材料工学専攻
(主査)教授足立裕彦, 教授牧正志, 教授山口正治
学位規則第4条第1項該当

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39

Haldar, T. "Spectroscopic determination of electrostatic and hydrogen bonding interaction in chemical and biological system." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2021. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/5991.

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40

Matito, i. Gras Eduard. "Development, implementation and application of electronic structural descriptors to the analysis of the chemical bonding, aromaticity and chemical reactivity." Doctoral thesis, Universitat de Girona, 2006. http://hdl.handle.net/10803/7940.

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En la literatura sobre mecànica quàntica és freqüent trobar descriptors basats en la densitat de parells o la densitat electrònica, amb un èxit divers segons les aplicacions que atenyin. Per tal de que tingui sentit químic un descriptor ha de donar la definició d'un àtom en una molècula, o ésser capaç d'identificar regions de l'espai molecular associades amb algun concepte químic (com pot ser un parell solitari o zona d'enllaç, entre d'altres). En aquesta línia, s'han proposat diversos esquemes de partició: la teoria d'àtoms en molècules (AIM), la funció de localització electrònica (ELF), les cel·les de Voroni, els àtoms de Hirshfeld, els àtoms difusos, etc.
L'objectiu d'aquesta tesi és explorar descriptors de la densitat basats en particions de l'espai molecular del tipus AIM, ELF o àtoms difusos, analitzar els descriptors existents amb diferents nivells de teoria, proposar nous descriptors d'aromaticitat, així com estudiar l'habilitat de totes aquestes eines per discernir entre diferents mecanismes de reacció.
In the literature, several electronic descriptors based in the pair density or the density have been proposed with more or less success in their pratical applications. In order to be chemically meaningful the descriptor must give a definition of an "atom" in a molecule, or instead be able to identify some chemical interesting regions (such as lone pair, bonding region, among others). In this line, several molecular partition schemes have been put forward: atoms in molecules (AIM), electron localization function (ELF), Voronoi cells, Hirshfeld atoms, fuzzy atoms, etc.
The goal of this thesis is to explore the density descriptors based on the molecular partitions of AIM, ELF and fuzzy atom, analyze the existing decriptors at several levels of theory, propose new aromaticity descriptors, and study its ability to discern between different mechanisms of reaction.

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41

Xu, Xiao. "Experimental and theoretical charge density analysis of functionalized polyoxovanadates : toward a better understanding of chemical bonding and chemical reactivity." Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2015. http://www.theses.fr/2015ECAP0026/document.

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Les polyoxovanadates fonctionalisés (POVs) présentent des structures de type cœur – cluster super-octahédral à l’échelle nanométrique, des propriétés électroniques et magnétiques facinantes, de nombreux isomers possédant des propriétés thermodynamiques de type réduction – oxydation et des applications catalytiques prometteuses. Parmi ces différentes propriétés, nous nous sommes intéressées aux propriétés de transfert de charge et de fluorescence. Cependant, comprendre des comportements de transfert de charge, et des mécanismes de fluorescence de ces héxavanadates fonctionnalisées est un encore véritable challenge.La diffraction des rayons X haute résolution permet l’analyse des propriétés électroniques et topologiques, et représente une méthode performante pour étudier les liaisons chimiques et la réactivité chimique, basées sur la détermination des propriétés électroniques et électrostatiques. Par conséquent ces propriétés ont été déterminées pour des polyoxovanadates et sont discutées au niveau atomique.Dans ce manuscrit, nous présentons les résultats de : i) la densité électronique expérimentale, la topologie et les propriétés électrostatiques de deux hexavanadates fonctionnalisées (V6), [(C4H9)4N]2[V6O13{(OCH2)3CCH2OCCH2CH3}2] (V6-C3) and Na2[V6O13{(OCH2)3CCH2OH}2]·3.5H2O (V6OH) ; ii) les calculs théoriques ab initio, d’une série de composés fonctionnalisées (V6) et du décavanadate (V10). Les informations chimiques déduites de l’analyse de la densité électronique sont utilisées pour une meilleure compréhension de la distribution de la densité de charge, des propriétés de fluorescences, du comportement en terme de fonctionnalisation, et des propriétés biologiques
The functionalized polyoxovanadates (POVs) exhibit nanoscale superoctahedral cluster-core structures, fascinating electronic and magnetic properties, various thermodynamically stable redox isomers, and potential catalytic capabilities. Among of the various properties, we are interested in the charge transfer and fluorescent properties. However, understanding such a charge transfer behavior and fluorescence mechanism of these functionalized hexavanadates is still a formidable challenge.High resolution X-ray crystallography allows the analysis of the electronic and topological properties, and provides a method to study the chemical bonding and chemical reactivity based on charge density and the electrostatic properties determination. Experimental and theoretical charge density analysis of functionalized polyoxovanadates has been carried out and the related properties have been discussed at the atomic level.In this manuscript, we present the results of: i) experimental charge density and related electronic and topological properties of two functionalized hexavanadates (V6), [(C4H9)4N]2[V6O13{(OCH2)3CCH2OCCH2CH3}2] (V6-C3) and Na2[V6O13{(OCH2)3CCH2OH}2]·3.5H2O (V6OH); ii) theoretical calculations on a series of functionalized V6 compounds, and decavanadate (V10). The chemical information from charge density analysis is used for a better understanding of the charge density distribution, charge transfer, fluorescent properties, functionalization behavior, and biological activities

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42

Determan, John J. Omary Mohammad A. "Computational studies of bonding and phosphorescent properties of group 12 oligomers and extended excimers." [Denton, Tex.] : University of North Texas, 2008. http://digital.library.unt.edu/permalink/meta-dc-9108.

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43

Cantalapiedra, Nuria Aboitiz. "Intramolecular hydrogen-bonding studies by NMR spectroscopy." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366715.

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44

Mirabile, Kyle Vincent. "Investigating Differences in Douglas-fir and Southern Yellow Pine Bonding Properties." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/56970.

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Анотація:

Differences in southern yellow pine (represented by Pinus taeda) and Douglas-fir (Pseudotsuga menziesii) mature and juvenile wood were examined in terms of density, chemical composition, surface energy, shear stress, % wood failure, and delamination. Density was measured using a QTRS density scanner. Loblolly pine contained a higher average density. Chemical composition was measured using the NREL standard for identifying the chemical composition of biomass. Southern yellow pine contained a higher % hemicellulose, lignin, and extractives. Douglas-fir had higher % cellulose than southern yellow pine. Surface energy was measured using the static sessile drop contact angle method and the acid/base approach. Southern yellow pine contained a lower average contact angle than Douglas-fir. Shear stress, % wood failure, and durability were measured using ASTM-D2559 with two adhesives, a one-part moisture cure polyurethane (PU), and a two-part ambient curing phenol-resorcinol-formaldehyde (PRF). Shear stress for southern yellow pine was affected the most by the type of growth regions at the bond (juvenile to mature wood) and the assembly times of the adhesives used. Douglas-fir shear stress was affected by the type of adhesive and the growth region at the bond. Delamination results demonstrated that when using PRF the southern yellow pine has less delamination statistically than Douglas-fir. Also, the growth region at the bond with both adhesives showed to impact delamination with juvenile to mature wood having less delamination than mature to mature wood.
Master of Science

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45

Pabuccu, Aybuke. "Effect Of Conceptual Change Texts Accompanied With Analogies On Understanding Of Chemical Bonding Concepts." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/3/12605121/index.pdf.

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The purpose of this study was to explore the effects of CCTIA over TDCI for 9th grade students&rsquo
understanding of chemical bonding concepts. Also, the effect of instruction on students&rsquo
attitude toward chemistry as a school subject and the effect of gender difference on understanding of chemical bonding concepts and attitudes toward chemistry were investigated. The subjects of this study consisted of 41 ninth grade students from two classes of a chemistry course in TED Ankara High School. This study was conducted during the 2003-2004-spring semester. The classes were randomly assigned as control and experimental groups. Students in the control group were instructed by TDCI whereas students in the experimental group were instructed by CCTIA. CBCT was administered to both groups as a pre-test and post-test in order to assess their understanding of concepts related to chemical bonding. Students were also given ASTC as a school subject at the beginning and end of the study to determine their attitudes and SPST at the beginning of the study to measure their science process skills. At the end of the study, we administered interviews to the students. The hypotheses were tested by using ANCOVA and ANOVA. The results revealed that CCTIA caused a significantly better understanding of scientific conceptions related to chemical bonding concepts than the TDCI. In addition, these two modes of instruction developed the similar attitude toward science as a school subject. Also, science process skill was a strong predictor in understanding the concepts related to chemical bonding. Alternatively, no significant effect of gender difference on understanding the concepts about chemical bonding and on students&rsquo
attitudes toward chemistry as a school subject was found.

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46

Robertazzi, Arturo. "Quantum chemical studies of DNA and metal-DNA stuctures : H-bonding and P-stacking." Thesis, Cardiff University, 2006. http://orca.cf.ac.uk/56075/.

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Metal complexes interact with many different sites of nucleic acids, stabilising the structure or, in some cases, leading to severe distortion or non-canonical forms of DNA such as triplexes, quadruplexes, junctions etc. Remarkably, several transition metals are considered potentially active anti-cancer drugs. Among these the most studied is certainly cis-diamminodichloroplatinum(II), or cisplatin, which after an activation process, attacks DNA in guanine-rich regions leading to strong distortion of DNA structure. Theoretical and experimental works suggest 7t-stacking disruption and GC pair distortion as the most relevant effects. In this work, ab initio and DFT calculations are extensively employed in order to explore the role of basic forces in DNA and metal-DNA adducts. To do so, Atoms in Molecules (AIM) theory has been used as a tool to decompose binding energies into contributions of covalent bond, H-bond and rc-stack energies, leading to a clearer picture of the studied systems. Firstly, DFT methods were employed to investigate the hydrolysis mechanism of cisplatin, a key step in the activation of the drug. Subsequently, an ADM based approach has been proposed to estimate H-bond energies in metal-DNA complexes. This allowed us to investigate the effect of platination on GC pair and, more generally, the role of H-bonding in such systems. A large study of transition metal- purine complexes, from Ti to Hg, has been discussed, providing a systematic analysis of the effect of metallation on the GC pair. As well as H-bonding, 7c-stacking plays a fundamental role in DNA and metal-DNA structures. In order to avoid use of expensive and, in certain cases, prohibitive methods such as MP2 and CCSD calculations, a new hybrid DFT functional, BHandH, has been applied to stacked model complexes (from benzene to DNA nucleobases). In addition, AIM analysis was shown to be useful tool in estimating it-stacking interactions in these systems. Thus, QM/MM calculations (QM = BHandH, MM = AMBER) were employed in order to investigate the role of H-bonding and -stacking in DNA and cisplatin-DNA adducts, the interplay between those being our main focus. One example of realistic platinated octamer was also studied with the BH&H/AMBER/AIM approach, leading to general agreement with experimental data.

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47

BERTELSEN, CRAIG MICHAEL. "RUBBER-TO-METAL BONDING: AN INVESTIGATION OF CHEMICAL REACTIONS AND ADHESION AT THE INTERFACE." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin988042302.

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48

Liu, Haijing. "Wet adhesion properties of oilseed proteins stimulated by chemical and physical interactions and bonding." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/35774.

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Doctor of Philosophy
Department of Grain Science and Industry
X. Susan Sun
The ecological and public health liabilities related with consuming petroleum resources have inspired the development of sustainable and environmental friendly materials. Plant protein, as a byproduct of oil extraction, has been identified as an economical biomaterial source and has previously demonstrated excellent potential for commercial use. Due to the intrinsic structure, protein-based materials are vulnerable to water and present relatively low wet mechanical properties. The purpose of this study focuses on increasing protein surface hydrophobicity through chemical modifications in order to improve wet mechanical strength. However, most of the water sensitive groups (WSG), such as amine, carboxyl, and hydroxyl groups, are also attributed to adhesion. Therefore, the goal of this research is to reduce water sensitive groups to an optimum level that the modified soy protein presents good wet adhesion and wet mechanical strength. In this research, we proposed two major approaches to reduce WSG: 1). By grafting hydrophobic chemicals onto the WSGs on protein surface; 2). By interacting hydrophobic chemicals with the WSGs. For grafting, undecylenic acid (UA), a castor oil derivative with 11-carbon chain with a carboxyl group at one end and naturally hydrophobic, was used. Carboxyl groups from UA reacted with amine groups from protein and converted amines into ester with hydrophobic chains grafting on protein surface. The successful grafting of UA onto soy protein isolate (SPI) was proved by both Infrared spectroscopy (IR) and ninhydrin test. Wood adhesive made from UA modified soy protein had reached the highest wet strength of 3.30 ± 0.24 MPa with fiber pulled out, which was 65% improvement than control soy protein. Grafting fatty acid chain was verified to improve soy protein water resistance. For interaction approach, soy oil with three fatty acid chains was used to modify soy protein. Soy oil was first modified into waterborne polyurethanes (WPU) to improve its compatibility and reactivity with aqueous protein. The main forces between WPU and protein were hydrogen bonding, hydrophobic interactions, and physical entanglement. Our results showed that WPU not only increased protein surface hydrophobicity with its fatty acid chains but also enhanced the three-dimensional network structure in WPU-SPI adhesives. WPU modification had increased wet adhesion strength up to 3.81 ± 0.34 MPa with fiber pulled out compared with 2.01 ± 0.46 MPa of SPI. Based on IR and thermal behavior changes observed by DSC, it was inferred that a new crosslinking network formed between WPU and SPI. To exam if the UA and WPU technologies developed using soy protein are suitable for other plant proteins, we selected camelina protein because camelina oil has superior functional properties for jet fuels and polymers. Like soy protein, camelina protein is also highly water sensitive. However, simply applied UA and WPU to camelina protein following the same methods used for soy proteins, we did not obtain the same good adhesion results compared to what we achieved with soy protein. After protein structure analysis, we realized that camelina protein is more compact in structure compared to soy protein that made it weak in both dry and wet adhesion strength. Therefore, for camelina protein, we unfolded its compact structure with Polymericamine epichlorohydrine (PAE) first to improve flexible chains with more adhesion groups for future reaction with UA or WPU. PAE with charged groups interacted camelina protein through electrostatic interaction and promoted protein unfolding to increase reactivity within protein subunits and between protein and wood cells. Therefore, the wet adhesion strength of camelina protein was improved from zero to 1.30 ± 0.23 MPa, which met the industrial standard for plywood adhesives in terms of adhesion strength. Then the wet adhesion strength of camelina protein was further improved after applying UA and WPU into the PAE modified camelina protein. In addition, we also found PAE unfolding significantly improved the dry adhesion strength of camelina protein from 2.39 ± 0.52 to 5.39 ± 0.50 MPa with 100% wood failure on two-layer wood test. Camelina meal which is even more economical than camelina protein was studied as wood adhesive. Through a combination of PAE and laccase modification method, the wet adhesion strength of camelina meal was improved as high as 1.04 ± 0.19MPa, which also met industrial standards for plywood adhesives. The results of this study had proven successful modification of oilseed protein to increase water resistance and wet mechanical strength. We have gained in-depth understanding of the relationship between protein structure and wet adhesion strength. The successful modification of plant proteins meeting the industrial needs for bio-adhesives will promote the development of eco-friendly and sustainable materials.

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Schultze, Felix. "Coteaching chemical bonding with Upper secondary senior students : A way to refine teachers PCK." Licentiate thesis, Linköpings universitet, Lärande, Estetik, Naturvetenskap (LEN), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-152778.

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The aim of this study was to investigate how an experienced chemistry teacher gains and refines her pedagogical content knowledge (PCK) by cooperating with two grade 12 students (age 18) as coteachers while teaching chemical bonding in a grade 10 Upper secondary class. The study has been conducted from a sociocultural perspective, especially Vygotsky’s zone of proximal development (ZPD) (Vygotsky, 1978). Other theoretical concepts and models that has framed this study are Shulman´s Pedagogical content knowledge (PCK) and Pedagogical reasoning and action model (Shulman, 1986, 1987). When analysing the data, Magnusson, Krajcik, and Borko´s (1999) model of PCK and the 2017 Refined consensus model of PCK (Carlson, Daehler, et al., in press) was used. Empirical data was collected by video- and audio recorded lessons, coreflection sessions, coplanning sessions and interviews. During 10 weeks, about 28 hours of video and audio recordings was collected. Selected parts of the material were transcribed and analysed in order to answer two questions: (1) How can chemistry teachers refine their PCK when coteaching together with senior students in an Upper secondary science class? (2) How do Upper secondary senior student coteachers´ conceptual knowledge of representations and chemical bonding shape a teacher’s foundation of personal PCK (pPCK) when teaching chemical bonding in an Upper secondary science class? The results relating to research question one indicates that the coteachers contributed with their own learning experiences to help the teacher understand how students perceive difficult concepts. The coteachers were mediating between the teacher and the students, thus bridging the gap between the teacher and the students’ frames of references. The experienced chemistry teacher improved her understanding of students´ thinking about themselves as learners of chemical bonding. Regarding the second research question, the findings showed that the creative process of reconstructing concepts of chemical bonding in the coplanning sessions meant that these were a useful tool for developing new teaching strategies and to further develop representations such as drama to illustrate chemical bonding. Together, the teacher and student coteachers, constructed a new representation that better illustrated polar covalent bonding. Taken together, these results provide important insights into how the chemistry teacher´s pPCK was refined and how the coteachers contributed to improve instructional strategies.

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Zubarev, Dmitry Yu. "Analysis of Chemical Bonding in Clusters by Means of The Adaptive Natural Density Partitioning." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/13.

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Models of chemical bonding are essential for contemporary chemistry. Even the explosive development of the computational resources including, both hardware and software, cannot eliminate necessity of compact, intuitive, and efficient methods of representing chemically relevant information. The Lewis model of chemical bonding, which was proposed eleven years before the formulation of quantum theory and preserves its pivotal role in chemical education and research for more than ninety years, is a vivid example of such a tool. As chemistry shifts to the nanoscale, it is becoming obvious that a certain shift of the paradigms of chemical bonding is inescapable. For example, none of the currently available models of chemical bonding can correctly predict structures and properties of sub-nano and nanoclusters. Clusters of main-group elements and transition metals are of major interest for nanotechnology with potential applications including catalysis, hydrogen storage, molecular conductors, drug development, nanodevices, etc. Thus, the goals of this dissertation were three-fold. Firstly, the dissertation introduces a novel approach to the description of chemical bonding and the algorithm of the software performing analysis of chemical bonding, which is called Adaptive Natural Density Partitioning. Secondly, the dissertation presents a series of studies of main-group element and transition-metal clusters in molecular beams, including obtaining their photoelectron spectra, establishing their structures, analyzing chemical bonding, and developing generalized model of chemical bonding. Thirdly, the dissertation clarifies and develops certain methodological aspects of the quantum chemical computations dealing with clusters. This includes appraisal of the performance of several computational methods based on the Density Functional Theory and the development of global optimization software based on the Particle Swarm Optimization algorithm.

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