Dissertations / Theses: 'Physical Chemistry'

1

Sanders, Jacob N. "Compressed Sensing for Chemistry." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493432.

Full text

Abstract:

Many chemical applications, from spectroscopy to quantum chemistry, involve measuring or computing a large amount of data, and then compressing this data to retain the most chemically-relevant information. In contrast, compressed sensing is an emergent technique that makes it possible to measure or compute an amount of data that is roughly proportional to its information content. In particular, compressed sensing enables the recovery of a sparse quantity of information from significantly undersampled data by solving an l1-optimization problem. This thesis represents the application of compressed sensing to problems in chemistry. The first half of this thesis is about spectroscopy. Compressed sensing is used to accelerate the computation of vibrational and electronic spectra from real-time time-dependent density functional theory simulations. Using compressed sensing as a drop-in replacement for the discrete Fourier transform, well-resolved frequency spectra are obtained at one-fifth the typical simulation time and computational cost. The technique is generalized to multiple dimensions and applied to two-dimensional absorption spectroscopy using experimental data collected on atomic rubidium vapor. Finally, a related technique known as super-resolution is applied to open quantum systems to obtain realistic models of a protein environment, in the form of atomistic spectral densities, at lower computational cost. The second half of this thesis deals with matrices in quantum chemistry. It presents a new use of compressed sensing for more efficient matrix recovery whenever the calculation of individual matrix elements is the computational bottleneck. The technique is applied to the computation of the second-derivative Hessian matrices in electronic structure calculations to obtain the vibrational modes and frequencies of molecules. When applied to anthracene, this technique results in a threefold speed-up, with greater speed-ups possible for larger molecules. The implementation of the method in the Q-Chem commercial software package is described. Moreover, the method provides a general framework for bootstrapping cheap low-accuracy calculations in order to reduce the required number of expensive high-accuracy calculations.
Chemical Physics

APA, Harvard, Vancouver, ISO, and other styles

2

McClean, Jarrod Ryan. "Algorithms Bridging Quantum Computation and Chemistry." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17467376.

Full text

Abstract:

The design of new materials and chemicals derived entirely from computation has long been a goal of computational chemistry, and the governing equation whose solution would permit this dream is known. Unfortunately, the exact solution to this equation has been far too expensive and clever approximations fail in critical situations. Quantum computers offer a novel solution to this problem. In this work, we develop not only new algorithms to use quantum computers to study hard problems in chemistry, but also explore how such algorithms can help us to better understand and improve our traditional approaches. In particular, we first introduce a new method, the variational quantum eigensolver, which is designed to maximally utilize the quantum resources available in a device to solve chemical problems. We apply this method in a real quantum photonic device in the lab to study the dissociation of the helium hydride (HeH$^{+}$) molecule. We also enhance this methodology with architecture specific optimizations on ion trap computers and show how linear-scaling techniques from traditional quantum chemistry can be used to improve the outlook of similar algorithms on quantum computers. We then show how studying quantum algorithms such as these can be used to understand and enhance the development of classical algorithms. In particular we use a tool from adiabatic quantum computation, Feynman's Clock, to develop a new discrete time variational principle and further establish a connection between real-time quantum dynamics and ground state eigenvalue problems. We use these tools to develop two novel parallel-in-time quantum algorithms that outperform competitive algorithms as well as offer new insights into the connection between the fermion sign problem of ground states and the dynamical sign problem of quantum dynamics. Finally we use insights gained in the study of quantum circuits to explore a general notion of sparsity in many-body quantum systems. In particular we use developments from the field of compressed sensing to find compact representations of ground states. As an application we study electronic systems and find solutions dramatically more compact than traditional configuration interaction expansions, offering hope to extend this methodology to challenging systems in chemical and material design.
Chemical Physics

APA, Harvard, Vancouver, ISO, and other styles

3

Ngabe, Barnabe. "Physical chemistry of sulphide self-heating." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123024.

Full text

Abstract:

ABSTRACTA prerequisite step towards building a self-heating (SH) model for sulphide materials is the determination of physico-chemical parameters such as the specific heat capacity (Cp), and the energy of activation (Ea). The specific heat capacity of one copper and three nickel concentrates was determined over the temperature range 50 to 80oC in the presence of 6% moisture using the self-heating (SH) apparatus and confirmed by Drop Calorimetry. The Cp values from both techniques were comparable. The Cp values were similar for all concentrates increasing from 0.4 to 1.4 Jg-1K-1 as temperature increased from 50 to 80oC. From the Cp values, the enthalpy change (ΔH), the entropy change (ΔS) and the Gibbs free energy change (ΔG) for self-heating, were determined. The ΔG was negative, demonstrating that self-heating of the concentrates was spontaneous.Using the self-heating apparatus the, activation energy (Ea) was determined for the Ni-and Cu-concentrates and for pairs of sulphide minerals. The Ea ranged from 22 to 30 kJ.mol-1, implying a common reaction. Further support for a common reaction is the strong positive correlation between Ea and ln(QA/Cp) where Q (J.kg-1) is the heat of reaction causing self-heating and A the Arrhenius pre-exponential factor (s-1). Comparing to literature, the Ea values correspond to partial oxidation of hydrogen sulphide, supporting the contention that H2S may be an intermediate product in the self-heating of sulphide minerals. A positive relationship between Ea and the rest potential difference (ΔV) for the sulphide pairs and a negative relationship between Cp and ΔV were demonstrated which support a connection between self-heating and the galvanic effect.
RESUMÉLa réalisation d'un modèle mathématique de l'auto-échauffement des concentrés sulfurés de nickel et de cuivre et des mélanges des minerais sulfurés, enjoint à la détermination des paramètres physico-chimiques tels que les capacités de chaleur spécifiques (Cp), et les énergies d'activation (Ea). Les capacités de chaleur spécifiques d'un concentré de cuivre et de trois concentrés de nickel contenant 6% d'humidité, ont été déterminées par utilisation d'un instrument de mesure de vitesse d'auto – échauffement et validées par la calorimétrie de chute dans l'intervalle de températures allant de 50 à 80oC. Les Cp (0.4 à 1.4 Jg-1K-1) obtenues sont similaires pour tous les échantillons. A partir des valeurs des Cp, les variations de l'enthalpie (ΔH), l'entropie (ΔS) et de l'énergie libre de Gibbs (ΔG) de l'auto échauffement ont été déterminées. La valeur négative de ΔG confirme le caractère spontané de l'auto échauffement des minerais sulfurés.Les énergies d'activation (Ea) pour l'auto-échauffement des concentrés de nickel et cuivre et des paires de minerais sulfurés étaient déterminées en faisant usage de l'appareil d'auto-échauffement. Les Ea ainsi obtenues oscillent entre 22 et 30 kJ.mol-1 : Ce qui est suggestif d'une rèaction chimique commune gouvernant l'auto-échauffement de ces matériaux. Ce fait est corroboré par la forte corrélation obtenue entre Ea et ln(QA/Cp) (Q (J.kg-1) est la chaleur de la rèaction chimique responsable de l'auto-échauffement et A (s-1) la constante d'Arrhenius).Ensuite celles-ci sont similaires à celle de l'oxydation partielle du H2S. Il se pourrait, ce faisant, que H2S soit un composé intermediaire lors de l'auto–échauffement des sulfures.Enfin, la corrélation positive entre Ea et la difference de potential (ΔV) dans les paires de minerais sulfurés et celle negative entre Cp et ΔV sont une preuve qu'il existe bel et bien une connection entre l'auto-échauffement et l'effet galvanique.

APA, Harvard, Vancouver, ISO, and other styles

4

Christy, R. K. "The physical chemistry of drug formulations." Thesis, University of Kent, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362185.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Das, Ujjal. "Electronic structure studies of semiconductor surface chemistry and aluminum oxide cluster chemistry." [Bloomington, Ind.] : Indiana University, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3344570.

Full text

Abstract:

Thesis (Ph. D.)--Indiana University, Dept. of Chemistry, 2008.
Title from PDF t.p. (viewed Oct. 7, 2009). Source: Dissertation Abstracts International, Volume: 70-02, Section: B, page: 1054. Adviser: Krishnan Raghavachari.

APA, Harvard, Vancouver, ISO, and other styles

6

Babbush, Ryan Joseph. "Towards Viable Quantum Computation for Chemistry." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17467325.

Full text

Abstract:

Since its introduction one decade ago, the quantum algorithm for chemistry has been among the most anticipated applications of quantum computers. However, as the age of industrial quantum technology dawns, so has the realization that even “polynomial” resource overheads are often prohibitive. There remains a large gap between the capabilities of existing hardware and the resources required to quantum compute classically intractable problems in chemistry. The primary contribution of this dissertation is to take meaningful steps towards reducing the costs of three approaches to quantum computing chemistry. First, we discuss how chemistry problems can be embedded in Hamiltonians suitable for commercially manufactured quantum annealing machines. We introduce schemes for more efficiently compiling problems to annealing Hamiltonians and apply the techniques to problems in protein folding, gene expression, and cheminformatics. Second, we introduce the first adiabatic quantum algorithm for fermionic simulation. Towards this end, we develop tools which embed arbitrary universal Hamiltonians in constrained hardware at a reduced cost. Finally, we turn our attention to the digital quantum algorithm for chemistry. By exploiting the locality of physical interactions, we quadratically reduce the number of terms which must be simulated. By analyzing the scaling of time discretization errors in terms of chemical properties, we obtain significantly tighter bounds on the minimum number of time steps which must be simulated. Also included in this dissertation is a protocol for preparing configuration interaction states that is asymptotically superior to all prior results and the details of the most accurate experimental quantum simulation of chemistry ever performed.
Chemical Physics

APA, Harvard, Vancouver, ISO, and other styles

7

Grimes-Marchan, Thomas V. Cundari Thomas R. "Quantum perspectives on physical and inorganic chemistry." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-5172.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Portal, Christophe. "Approaches to high throughput physical organic chemistry." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/2434.

Full text

Abstract:

Over the past ten years, the development of High Throughput (HT) synthetic chemistry techniques has allowed the rapid preparation of libraries of hundreds to thousands of compounds. These tools are now extensively used for drug and material discovery programmes. The subsequent development of analytical capabilities to carry out qualitative and quantitative assessment of the compounds generated by HT synthesis as well as their HT screening has led to a dramatic broadening of the scope of HT techniques, ranging from image based analysis techniques to mass spectrometry (MS). Based on the latter, a range of solid phase and solution phase analytical constructs was developed to enable the qualitative and quantitative assessment of mixtures of small compounds, using positive electrospray MS as the sole analytical tool. A version of the construct allowed HT reactivity profiling to be carried out on a range of ten carboxylic acids, ten aldehydes and ten isonitriles in the Ugi 4-component condensation reaction. The effect of various parameters such as the concentration of the monomers on the reactivity was investigated. The elaboration of a HT Hammett parameter assessment method was made possible by the development of an electrophilic version of the construct. The value of the Hammett value was afforded by means of combinatorial Hammett plots and values were successfully evaluated in a HT mode for around thirty anilines with substituents in the meta and para position of the aromatic ring. Finally, analytical constructs were used in an attempt to evaluate enzyme reaction kinetics via the labelling of peptides and small drug fragment with coded constructs, to afford affinity determinations between the enzyme (protease) and peptidic or fragment based substrates.

APA, Harvard, Vancouver, ISO, and other styles

9

Slocum, Laura Elizabeth. "Evaluation of physical chemistry on-line modules." Virtual Press, 2001. http://liblink.bsu.edu/uhtbin/catkey/1221309.

Full text

Abstract:

We have modeled in one-dimension two-dimensional (2-D) quantum wire structures: the notched electron stub tuner (NEST) and the double-notched electron stub tuner (D-NEST). The models consisted of square barriers representing the notches and square wells representing the stubs. We have calculated the transmission coefficient as a function of electron energy and/or device geometries to study electron transport through these quantum wire models. The transfer matrix method was used to calculate the transmission coefficient by utilizing a program written with Mathematica. The program and technique were verified using one-dimensional systems from the literature.We studied the principle of wave interference in the NEST model in the form of intersection points of several curves of the transmission coefficient versus barrier/well separation plotted with no offset. The creation of standing waves, in certain regions of the NEST model, by the interference of incident and reflected waves, gives rise to these intersection points. We have identified features in the conductance curves of the NEST and the transmission coefficient curves of the NEST model (the intersection points) that are very similar and may be explained by the same principle of wave interference.We have studied double-barrier resonant tunneling (DBRT) to assist in our study of the D-NEST model. The resonances in DBRT are attributed to the creation of standing waves between the two barriers for the tunneling and non-tunneling regimes. We attempted to prove the existence of these standing waves by studying the probability density in the D-NEST model. The well of the D-NEST model was scanned down the length of the double-barrier well region to investigate its effect on the transmission coefficient for this purpose. A small square barrier, used as a probe, was also used to study the probability density in the same way as the well was used. Initial scans of the probe above a simple square barrier gave us insight into the possibility of using it to scan for the probability density in the well region. The "over-the-barrier" resonances (attributed to standing waves) were studied in this case.We have developed knowledge of the transmission properties of these models that may aid in the understanding of the electron transport through the 2-D devices. We believe that to "fine tune" the conductance output of the D-NEST device, the second notch should be placed at a location that permits the creation of standing waves, for a specific electron energy value, between the two notches of the device. The "fine tuning" of the conductance output into a square-wave pattern could improve the devices performance as a potential switching mechanism.
Department of Chemistry

APA, Harvard, Vancouver, ISO, and other styles

10

Frank, Robert A. "Physical chemistry of carbothermic reduction of alumina." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15150.

Full text

Abstract:

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1985.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE
Vita.
Bibliography: leaves 177-180.
by Robert A. Frank.
M.S.

APA, Harvard, Vancouver, ISO, and other styles

11

Grimes-Marchan, Thomas V. "Quantum Perspectives on Physical and Inorganic Chemistry." Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc5172/.

Full text

Abstract:

Applications of computational quantum chemistry are presented, including an analysis of the photophysics of cyclic trinuclear coinage metal pyrazolates, an investigation into a potential catalytic cycle utilizing transition metal scorpionates to activate arene C-H bonds, and a presentation of the benchmarking of a new composite model chemistry (the correlation consistent composite approach, ccCA) for the prediction of classical barrier heights. Modeling the pyrazolate photophysics indicates a significant geometric distortion upon excitation and the impact of both metal identity and substituents on the pyrazolates, pointing to ways in which these systems may be used to produce rationally-tuned phosphors. Similarly, thermodynamic and structural investigations into the catalyst system points to promising candidates for clean catalytic activation of arenes. The ccCA was found to reproduce classical reaction barriers with chemical accuracy, outperforming all DFT, ab initio, and composite methods benchmarked.

APA, Harvard, Vancouver, ISO, and other styles

12

Jones, Ruth. "Chemistry of oxide superconductors." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304252.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Cooper, Philip Andrew. "Surface chemistry of foams." Thesis, University of Hull, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335544.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Bell, Douglas Hindmarsh. "Physical chemistry of liquid salt systems involving uranium." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/8248.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Wan, Nan Chi. "Physical organic chemistry of N-substituted N'-cyanoguanidines." Thesis, University of Surrey, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308493.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Parker, Andrew Philip. "The physical and colloidal chemistry of phosphorylcholine surfactants." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368722.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Duckenfield, Kea U. "Laboratory oxide coatings: Physical form and surface chemistry." W&M ScholarWorks, 2003. https://scholarworks.wm.edu/etd/1539616635.

Full text

Abstract:

The impact of dissolved trace metals on aquatic ecosystems and human health is controlled by sorption, i.e., binding to the surfaces of environmental particles. Since many environmental particles are coated with highly reactive substances, and since discrepancies in trace metal sorption behavior persist between oxides developed in the laboratory and environmental oxide phases, it was hypothesized that the physical form of oxide coatings may influence the chemical properties of the coated particle. Therefore, relationships between the physical forms of several different Fe(III) oxide coatings and the Cu(II) sorption behavior of the coated solids were investigated in comparison with the component phases and natural sedimentary materials. Goethite (alpha-FeOOH) was coated onto quartz and kaolinite grains. Coating method and thickness were varied. Physical properties of the coated solids were probed using multipoint N2 (g) adsorption and desorption analysis (BET), The morphology of the particles was studied by scanning electron microscopy (SEM), and the uniformity of oxide distribution on the grain surfaces was assessed by energy-dispersive X-ray (EDS) analysis. Chemical properties were investigated via batch Cu(II) adsorption/desorption experiments. Goethite physical form was found to vary with coating method and substrate mineralogy. Cu(II) sorption (uptake and release of dissolved Cu from goethite-coated particles) depended on the coating method, substrate, and thickness of the coating. Analysis of these variations indicated physical changes in the form of the coating, interactions between goethite and substrate, and changes in the surface chemical properties of one or both solid phases (goethite and substrate). The combined physical and chemical alterations in the properties of the solids produced distinct behavior in each of the laboratory-prepared solids studied. A parallel set of experiments was conducted on three geologically related sedimentary materials. Several physical and chemical differences were observed between crude kaolin and a cleaned reference kaolinite. One laboratory-prepared goethite coating matched a surface soil at precipitation-dominated Cu loadings, and another coated solid matched a subsurface material at all Cu loading ranges sampled. These results suggest that more complex laboratory-prepared sorbent phases may better reflect trace metal sorption properties of environmental particles.

APA, Harvard, Vancouver, ISO, and other styles

18

Kimber, Marc Colin. "The synthesis and physical chemistry of zinquin analogues /." Title page, table of contents and abstract only, 1998. http://web4.library.adelaide.edu.au/theses/09PH/09phk488.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Keene, Frank Richard. "Aspects of coordination chemistry /." Title page, contents and abstract only, 1998. http://web4.library.adelaide.edu.au/theses/09SD/09sdk26.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Srinivasan, Narmatha. "Preparative chemistry in ionic liquids." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287389.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

O'Brien, Stephen. "The chemistry of mesoporous materials." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390532.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Kennedy, P. A. "Chemistry of sodium-caesium solutions." Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355439.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Strange, Robin. "Electron correlation in quantum chemistry." Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289793.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Brown, Ken D. "The surface chemistry of beryllium." Thesis, University of Salford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333978.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Murray, Christopher William. "Quantum chemistry for large molecules." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317841.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Zysman-Colman, Eli. "The chemical and physical properties of polychalcogens." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84864.

Full text

Abstract:

The optimized synthesis of acyclic dialkoxy disulfides and aromatic polysulfides is described and their physical properties probed. A theoretical survey of dialkoxy disulfides and thionosulfites was undertaken in order to determine the most efficacious method for accurately modeling these compounds. In particular, the origin of the high barrier to rotation in the dialkoxy disulfides was determined to be due to a generalized anomeric effect resulting from two lone pair donations of each sulfur atom into each of their respective sulfur-oxygen antibonding orbitals. The origin of the high rotational barrier was also verified experimentally, in particular with respect to solvent and substituent effects. Complimentary to this thermal process, the decomposition of dialkoxy disulfides was also investigated. It was determined that these compounds decompose under first order kinetics via an initial asymmetric S-O homolytic cleavage. Activation parameters for both of these processes were determined.
Theoretical modeling on the relative ground state energies of dialkoxy disulfides is also described. It has been ascertained that the equilibrium position between the two isomers can be influenced by the ring size of the molecule; larger rings promote the dialkoxy disulfide isomer. These modeling studies were successfully corroborated experimentally. Of note is the synthesis of a new 8-membered ring dialkoxy disulfides as well as novel 7-membered ring thionosulfites. These compounds were also confirmed by single X-ray crystallography.
The kinetics of desulfurization of acyclic aromatic tri- and tetrasulfides is described. Tetrasulfides were found to transfer a sulfur atom to triphenylphosphine over ten times faster than their trisulfide analogues.

APA, Harvard, Vancouver, ISO, and other styles

27

Lu, Jian Ren. "The surface chemistry of emulsion breakdown." Thesis, University of Hull, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384850.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Griffiths, Stephen Paul. "Modification chemistry for chiral heterogeneous catalysts." Thesis, University of Hull, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390370.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Creaser, Dale Abel. "Aspects of composite lanthanide oxide chemistry." Thesis, University of Nottingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334547.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Knowles, James Atherton. "Chemistry and electrochemistry with zirconium phosphate." Thesis, University of Exeter, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317640.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Peacock, Heather Margaret. "Solid state oxide chemistry of ruthenium." Thesis, University of Aberdeen, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257552.

Full text

Abstract:

The oxygen stoichiometry of RuO_{2+atop -x} was investigated by thermogravimetric and isopiestic techniques, in the temperature range 200-800^oC. RuO_{2+atop -x} could be made hyperstoichiometric to a maximum of RuO_2.014 at 500^oC and hypostoichiometric to a maximum of RuO_1.9808 at 600^oC. Above 800^oC loss of ruthenium as the volatile species RuO₃(g) and RuO₄(g) prevented any reasonable determination of oxygen stoichiometry. Solid solutions were prepared in the Ru-V-O, Ru-Nb-O, Ru-W-O and Ru-Mo-O systems by solid state reaction. Complete solid solution was observed in the Ru-V-O system. Unit cell parameters were determined by X-ray powder diffraction for a range of compositions in the Ru-V-O system. Large deviations from the linearity predicted by Vegard's law were found for both a and c, e.g. at 5 wt.% vanadium a = 4.489, c = 3.089 and at 75 wt.% vanadium a = 4.592, c = 2.873. Conductivity of polycrystalline pressed pellets of RuO₂:VO₂ solid solutions was measured using a four point probe technique. All small vanadium concentrations conductivity increased with percent dopant i.e. resistivity decreased from 8.5 k Ω cm at 2 wt.% vanadium to 4.5 k Ω cm at 5 wt.% vanadium. Solid solutions containing 25-85 wt.% vanadium were found to be semiconducting and increasing amounts of vanadium in this range produced no significant change in resistivity. Solid solutions containing 95 wt.% vanadium showed a transition, at -13^oC, from metallic to semiconducting behaviour as the temperature was lowered. In the Ru-Nb-O, Ru-W-O and Ru-Mo-O systems only 5 wt.% dopant could be successfully incorporated into the RuO₂ lattice. On the basis of the Ru-V-O system however these materials are considered to be potentially good conductors. Resistor inks dilute in ruthenium could prove economically viable. The high vanadium containing materials may have potential as temperature sensitive electronic switching devices. The temperature programmed reduction of an RuO₂:VO₂ solid solution containing 25 wt.% vanadium showed that the onset of reduction occurred at a much higher temperature (234^oC) than for RuO₂ itself (63^oC). This suggests that vanadium containing solid solutions of RuO₂ are more resistant to reduction than RuO₂ itself, a much sought after property in the production of thick film resistors.

APA, Harvard, Vancouver, ISO, and other styles

32

Harrison, James Thomas Henry. "Electrical discharge chemistry of nitrogen oxides." Thesis, University of York, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292592.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Dyer, James U. "Evaluation of physical chemistry in practice (PCIP) DVD modules." Virtual Press, 2005. http://liblink.bsu.edu/uhtbin/catkey/1318447.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Stewart, Laura. "Physical studies of diphytanylglycerol phospholipids." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5405.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Cacha, Brian Joseph Gonda. "Metallic nanoparticle deposition techniques for enhanced organic photovoltaic cells." Thesis, California State University, Long Beach, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1598627.

Full text

Abstract:

Energy generation via organic photovoltaic (OPV) cells provide many advantages over alternative processes including flexibility and price. However, more efficient OPVs are required in order to be competitive for applications. One way to enhance efficiency is through manipulation of exciton mechanisms within the OPV, for example by inserting a thin film of bathocuproine (BCP) and gold nanoparticles between the C₆₀/Al and ZnPc/ITO interfaces, respectively. We find that BCP increases efficiencies by 330% due to gains of open circuit voltage (V_oc) by 160% and short circuit current (J_sc) by 130%. However, these gains are complicated by the anomalous photovoltaic effect and an internal chemical potential. Exploration in the tuning of metallic nanoparticle deposition on ITO was done through four techniques. Drop casting Ag nanoparticle solution showed arduous control on deposited morphology. Spin-coating deposited very low densities of nanoparticles. Drop casting and spin-coating methods showed arduous control on Ag nanoparticle morphology due to clustering and low deposition density, respectively. Sputtered gold on glass was initially created to aid the adherence of Ag nanoparticles but instead showed a quick way to deposit aggregated gold nanoparticles. Electrodeposition of gold nanoparticles (AuNP) proved a quick method to tune nanoparticle morphology on ITO substrates. Control of deposition parameters affected AuNP size and distribution. AFM images of electrodeposited AuNPs showed sizes ranging from 39 to 58 nm. UV-Vis spectroscopy showed the presence of localized plasmon resonance through absorption peaks ranging from 503 to 614 nm. A linear correlation between electrodeposited AuNP size and peak absorbance was seen with a slope of 3.26 wavelength(nm)/diameter(nm).

APA, Harvard, Vancouver, ISO, and other styles

36

Bulsink, Philip. "Exploring the Chemistry of Re(I): Physical and Theoretical Investigations." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32065.

Full text

Abstract:

The development of Rhenium I photocatalysts has been pursued since Lehn first showed the excellent performance of the ReI bipyridine tricarbonyl catalyst. Since then, devel- opment has modified the organic ligand to demonstrate continued or improved activity with other α-diimine bidentate geometries. Geometry has been limited to bidentate motifs, with fac-(CO)3 and axial halides. This work will demonstrate the synthesis, characterization, and testing of a new terdentate, κ3(L3)−Re1(CO)2X (X = Cl, Br, CN, OTf) family of compounds for CO2 reduction, as well as computational investigations into the mechanism of the reduction of CO2 to CO and other species. Development of computational aides will be described as well.

APA, Harvard, Vancouver, ISO, and other styles

37

Anderson, Bryce L. "Advanced Physical Techniques in Inorganic Chemistry: Probing Small Molecule Activation." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493292.

Full text

Abstract:

Robust and efficient catalysts are necessary for realizing chemical energy storage as a solution for the intermittency associated with renewable energy sources. To aid in the development of such catalysts, physical methods are used to probe the photochemistry of small molecule activation in the context of solar-to-fuels cycles. Three systems are studied in the context of HX splitting (X=Br, Cl): polypyridyl nickel complexes, NiX3(LL) (LL = bidentate phosphine) complexes, and dirhodium phosphazane complexes. Two systems are studied in the context of dioxygen activation: cryptand-encapsulated peroxide dianion and cubane models of cobalt water oxidation catalysts. Nickel complexes are shown to facilitate photo-driven H2 evolution from solutions containing HCl. Transient absorption (TA) reveals that polypyridyl ligands act as redox mediators, circumventing the inherently short excited state lifetimes common to first row transition metal complexes. By coupling the one-electron photochemistry of the polypyridyl ligands to disproportionation of reduced nickel complexes, two-electron chemistry is achieved. Halogen photoelimination is studied in a series of NiX3(LL) complexes which eliminate halogen in both solution and the solid state. Computation shows that efficient halogen photoelimination is facilitated by a dissociative LMCT excited state. TA identifies an aryl-halide complex as an intermediate in the photoelimination reaction. Halogen photoelimination from valence isomeric dirhodium phosphazane complexes, Rh2[I,III] and Rh2[II,II], is studied using TA and photocrystallography. TA suggests a common photo-intermediate that is probed by photocrystallography to reveal structural changes associated with transition to the proposed common intermediate. Oxygen activation chemistry is studied using the first soluble form of peroxide dianion. The kinetics of peroxide dianion oxidation are studied by leveraging the dianion’s propensity to form ion pairs with ruthenium polypyridyl complexes. TA kinetic data and DFT calculations facilitate a Marcus analysis which shows that the O–O bond of the peroxide dominates the internal reorganization energy. Cubane model complexes structurally related to the CoPi water oxidation catalyst are studied using TA and computations. Photooxidation by a covalently linked photosensitizer exhibits fast electron transfer rates. Calculations show extensive delocalization of the cubane molecular orbitals and examination of the excited state manifold implicates d–d excited states as facilitators of rapid charge transfer.
Chemistry and Chemical Biology

APA, Harvard, Vancouver, ISO, and other styles

38

Van, Delinder Kurt William. "The investigation of the molecular mechanism of rhodopsin activation by small angle neutron scattering and small angle x-ray scattering techniques." Thesis, Wayne State University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1604674.

Full text

Abstract:

Rhodopsin is a visual pigment found within the rod photoreceptor cells of the retina. It is a visual protein found within human beings and commonly shared amongst other vertebrate species. The major pigment protein is responsible for converting photons into chemical signals, which stimulates biological processes in the nervous system, and this allows the ability to then sense light.

The process of how rhodopsin is activated is believed to be understood with the introduction of a time ordered sequence of intermediate states. However, there are still major gaps and inconsistencies regarding the large-scale conformational changes that follow photoactivation.

The purpose of our experimental research is to use small angle neutron and x-ray scattering techniques to illuminate the structural changes and dynamics of rhodopsin that lead to the activation of the photoreceptor, and thus triggering of the amplified visual response.

APA, Harvard, Vancouver, ISO, and other styles

39

Samin, Adib J. Jr. "A statistical analysis of the rotational structure of the benzyl radical." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1405340209.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Goldsmith, Cory Scott. "Analytical Modeling and Numerical Simulations of Time Delays in Attosecond Streaking of One- and Two-Photon Ionization." Thesis, University of Colorado at Boulder, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10978194.

Full text

Abstract:

The generation of attosecond-duration (1 as = 10^–18 s) coherent light through the process of high-order harmonic generation has opened the perspective for probing fundamental processes, such as photoionization, on the natural timescale of electron dynamics in matter. One probing technique is the attosecond streaking method, in which the momentum of the photoelectron is measured as a function of the time delay between the ionizing, attosecond extreme ultraviolet (XUV) pulse, and a weak, femtosecond near-infrared (NIR) pulse which streaks the momentum of the photoelectron, known as a streaking trace. The observed trace contains time information about the photoionization process in the form of a time offset to the vector potential of the streaking field, known as the streaking time delay. Theoretical simulations show that for one-photon ionization this time delay is accumulated by the photoelectron in the continuum when propagating away from the parent ion, whereas for resonant two-photon ionization there exists an additional absorption delay which depends on the properties of the XUV pulse. In this thesis, we use both analytical techniques and numerical simulations to study the contributions of the total time delay observed in streaking, and further explore applications of the streaking time delay to gain insights into the electron dynamics. We first derive an analytical formula for the streaking time delay in one-photon ionization. The predictions based on the model formula, which can be performed within seconds of computation time, are in good agreement with those of computationally extensive numerical simulations.

We demonstrate that the analytical formula not only allows deeper insight into the nature of the time delay, but also offers the opportunity to effectively analyze other theoretical interpretations and potential effects, such as the effect of a chirp in the ionizing attosecond pulse on the time delay measurement. We then apply time-dependent perturbation theory to derive an analytical formula for the absorption delay in resonant two-photon ionization. We use the analytical formula to demonstrate how the absorption delay can be controlled further by the attosecond pulse duration and central frequency in case of an isolated resonance. Furthermore, we show how multiple resonances within the bandwidth of the ionizing pulses as well as the streaking field influence the absorption delay in model systems as well as simple atoms and molecules. We conclude by exploring the option to apply isolated elliptically polarized attosecond pulses to obtain sub-attosecond temporal information via the observation of photoelectron angular distributions as a function of the ellipticity of the pulse.

APA, Harvard, Vancouver, ISO, and other styles

41

Jordan, Carly A. "Work Function Modification of Metal Electrodes via Printing of PEDOT:PSS and Carbon Nanotubes." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1440696711.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Momot, Konstantin Igorevitch 1970. "Studies of nuclear magnetic relaxation processes in paramagnetic metalloporphyrin complexes." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282591.

Full text

Abstract:

Temperature dependence of Nuclear Magnetic Resonance (NMR) chemical shifts and longitudinal and transverse relaxation times (T₁ and T₂) was studied for the pyrrole protons in a number of six-coordinate S = 1/2 iron(III) tetraphenylporphyrin (TPP) and tetramesitylporphyrin (TMP) complexes in the temperature range 190--310 K. In all complexes, temperature behavior of the chemical shifts and relaxation times is consistent with the presence of a low spin - high spin exchange caused by the dissociation of one axial ligand. In symmetric sterically hindered complexes, cyclic exchange induced by the synchronous rotation of axial ligands is also present. In all complexes, T₂s are considerably shorter than T₁s. Relaxation times in the TMP complexes are generally longer than corresponding values for the TPP complexes. Estimate of the electronic T₁ is given and mechanisms of nuclear relaxation are discussed. The rate of NOE buildup for a pair of pyrrole protons in [TMPFe(2-MeImH)₂]⁺ was measured; it is consistent with the Stokes rotational correlation time. A method is proposed to predict the detectability and optimum detection conditions of NOE between a pair of structurally rigid protons in similar complexes. Contrary to previous studies, no NOE is detected between pyrrole protons of two unsymmetrically substituted bis-N-methylimidazole Fe(III) TPP complexes. Two NMR approaches were utilized to measure the rate constant of axial ligand rotation in the TMP complex. Saturation transfer measurements yield overestimated rate constant. The measurement based on the temperature dependence of the T₂s(ΔH‡ = 48 ± 1 kJ/mol, ΔS‡ = -10 ± 6 J/K · mol) is consistent with previous studies. Modified MM2 potentials were also used to study the rotation of axial ligands in [TMPFe(1,2-Me₂Im)₂]⁺ and [TPPFe(1-MeIm)₂]⁺. Adiabatic potential energy surfaces (PES) for rotation of axial ligands were constructed for both complexes. Synchronous rotation of the axial ligands (ΔH‡ = 48 kJ/mol) is highly preferable in the TMP complex. For the TPP complex, the enthalpy barriers to synchronous and asynchronous rotation are 3.3 and 5.4 kJ/mol, respectively. The relationship between the orientation of axial ligands, distortion of metalloporphyrin core from planarity, and the bulkiness of axial ligands and porphyrin substituents is discussed.

APA, Harvard, Vancouver, ISO, and other styles

43

Back, Roberta. "Physical and electrochemical investigation of novel ultrathin films." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39784.

Full text

Abstract:

A study of novel ultrathin films is presented in two sections. The first section presents an investigation of several unconventional film-forming molecules at the air/water interface using the surface film balance apparatus. Strongly hydrophobic fullerenes (C$ sb{60}$ and C$ sb{70}$) were found to spread at the air/water interface to form Langmuir films of multilayer rather than monolayer thicknesses. The formation of these well-defined multilayers is independent of the initial surface density of the fullerene. The films adopt discrete thicknesses of 4-5 monolayer equivalents. The multilayer of the non-spherical C$ sb{70}$ exhibited a transition attributed to a reorientational process that was not observed with the C$ sb{60}$ multilayer. A calculation of the work of compression for the two fullerene films confirmed important differences between the C$ sb{60}$ and C$ sb{70}$ films. 1,3,5- Phenylene-based hydrocarbon starburst dendrimers were also found to form multilayer Langmuir films at the air/water interface. The formation of these multilayers, however, is dependent on the initial surface density of dendrimer, and believed to rely upon interpenetration amongst dendrimer molecules. Langmuir-Blodgett films of dendrimer co-spread with fatty acid were examined by Atomic Force Microscopy. A series of amorphous polyimides also appear to form multilayer Langmuir films, possibly because they adopt a conformation on the water surface that renders them more rigid than in the bulk material.
The second section describes the electrochemical and interfacial properties of two series of thiophene/ferrocene conjugates. The detailed electrochemistry of these compounds is described, including their electro-oxidative polymerization and the subsequent characterization of the polymer film. Their unique bifunctional nature leads to the formation of a polymer material that is intrinsically limited to the formation of monolayers. At the air/water interface, these molecules have a well-defined phase transition from a disordered state to an ordered state. Their oxidative polymerization was effected chemically at the air/water interface in both their expanded form, in which they are extended on the water surface, and a more condensed form, although it was observed to proceed more rapidly in the expanded form.
In both studies, the properties of the ultrathin films that are formed are discussed in the context of the transition from aggregates to bulk material. The implication of the present results is also discussed with respect to the nature of the surface tension measurement in the surface film balance experiment. Finally, the importance of an architecture imposed by the properties of the molecules such as that observed in the electropolymerization of the thiophene/ferrocene compounds is discussed.

APA, Harvard, Vancouver, ISO, and other styles

44

Yao, Jing Wen. "Systematic structural studies in metal complex chemistry." Thesis, Durham University, 1998. http://etheses.dur.ac.uk/5055/.

Full text

Abstract:

A procedure is presented for detecting geometrical preferences, deformations and interconversion pathways between different geometries for the transition metal coordination sphere ML(_n). A discrepancy index [R(_ang)(x)] was proposed initially to address the problems of dimensionality and permutation complexity in the systematic analysis of coordination sphere geometry with higher coordination numbers (n > 7). But it can also be used generally for the lower coordination numbers. A set of standard geometries for coordination numbers 2-9 are presented and the angles between the center point and each vertex for the polyhedra which are used to describe the coordination sphere geometries for coordination numbers 7-9 are idealised. These angles correspond to the metal-ligand valence angles in the coordination complex and are used as the standard values to measure the deviation of a real coordination sphere in the complex from these standard polyhedra. Geometry of each coordination sphere (ML(_7-9)) from the Cambridge Structural Database (CSD) is identified by the calculations of R(_ang)(x) values. Also the unique enumeration numbers of the ligands corresponding to each geometry can be derived over the n! ligand permutations. The different geometrical clusters and interconversion pathways from one to another are mapped in a designed two-dimensional plot. The symmetry coordinates and principal component analysis are initially applied in these higher coordination number systems. They not only map the clusters represented to those standard geometries in the different symmetric point groups but also provide and confirm the interconversion pathways between the different geometries. The other systematic study involves the analysis and correlation of the metal σ-π bond in the transition metal alkyne and alkene complexes from the CSD. Geometrical features of this specific bond are examined in the view of structure and some useful correlation between the key geometrical parameters are defined. Finally, X-ray crystal structure determinations are briefly described and the crystal structures of ten transition metal compounds in coordination numbers 4-6 are presented.

APA, Harvard, Vancouver, ISO, and other styles

45

Zhao, Zhongwei. "Free radical chemistry of iron(II) complexes." Thesis, University of Salford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315384.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Sanderson, Michael George. "Experimental and modelling studies of atmospheric chemistry." Thesis, University of York, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259802.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Crawford, Alasdair James. "A Chemistry Neutral Flow Battery Performance Model Development, Validation, and Application." Thesis, Portland State University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10096820.

Full text

Abstract:

A physical model for redox flow batteries is developed to estimate performance for any chemistry using parameters such as electrolyte conductivity and kinetic rate constants. The model returns the performance as a function of flow rate, current density, and state of charge. Two different models are developed to estimate the current density distribution throughout the electrode in order to evaluate physical performance of the battery. This is done using electrochemical parameters such as conductivity and kinetic rate constant. The models are analytical in order to produce a computationally cheap algorithm that can be used in optimization routines. This allows for evaluating the economic performance of redox flow batteries, and optimization of cost. The models are validated vs data and found to accurately predict performance in a V-V system for a wide variety of operating conditions.

APA, Harvard, Vancouver, ISO, and other styles

48

Lahiri, Abhishek. "Physical and Process Chemistry of Alkali Roasting of Titaniferous Minerals." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490971.

Full text

Abstract:

Worldwide titanium dioxide pigments are extracted from ilmenite, anatase and rutile minerals by sulphate and chloride processes. The disadvantages ofthe two processes are that each of them produces a large volume of toxic and hazardous wastes which cannot be disposed without an additional treatment step which is a difficult and expensive process. The shortage of high-grade titaniferous ores has not only increased the production cost but also reduced the efficiency of the current sulphate and chloride processes. The present investigation shows a new beneficiationÃ‚Â· process based on the roasting of titaniferous minerals followed by leaching. Prior to alkali roasting, the phase decomposition of ilmenite was studied in detail using TGA, DTA, SEM and TEM techniques under different atmospheric conditions. Roasting of ilmenite ore with alkali was conducted with different alkalis such as sodium carbonate, bicarbonate and hydroxide. Similar experiments were conducted by changing the cation from. sodium to lithium and potassium to understand the influence of different cations on the roasting chemistry, removal of major, minor and trace impurities. During roasting, process parameters such as alkali to ore ratio, roasting time and temperature were varied and the change in the crystal structure were ascertained using XRD, SEM, and EDX techniques. The roasting reaction kinetics was analysed and thermodynamic calculations were carried out to study the various roasting reactions which led to the understanding of the roasting mechanism. Alkali roasting was followed by reduction leaching in which the roasted product was leached in a solution of oxalic and ascorbic acids to produce synthetic rutile. The reaction mechanism of the leaching process was studied in detail using FTIR. The results of this research work show a new method of beneficiating titaniferous ores by removing most of the impurities including the rare earths from the mineral ore to produce synthetic rutile of greater than 95% Ti02 concentration.

APA, Harvard, Vancouver, ISO, and other styles

49

Milton, D. M. P. "Applications of mass spectrometry in physical, organic and inorganic chemistry." Thesis, Swansea University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638196.

Full text

Abstract:

Proton transfer reactions to monosubstituted benzenes have been studied in the gas phase as a function of protonation exothermicity using tandem mass spectrometry. The results have been interpreted in terms of competitive ring and substituent protonation and intramolecular proton migration with the aid of molecular orbital calculations. It is shown that during the reaction of CHs⁺ with fluorobenzene at temperatures less than 330K, proton transfer occurs preferentially to the F atom even though its proton affinity is approximately 180kJmol^-1 less than the ring. Samples of ruthenium dioxide hydrate have been studied using the technique of mass spectral thermal analysis, before and after thermal activation. Two types of chemically bound water are identified, of which the loss of one is associated with the thermal activation. Headspace analysis of isotopically enriched gases evolved during reactions of these two forms indicates that the decomposition products contain oxygen atoms originating from the solvent. A glow discharge ion source has been constructed to fit an MS9 mass spectrometer. This source has been demonstrated to compare well with previous configurations for the analysis of metals in pin form. Fundamental studies show that the majority of the sputtering flux is observed to possess low energies, due to de-energising symmetrical charge transfer reactions in the cathode dark space. Ions of the cathode material possess higher energies, and it appears that sputtering of the cathode is mainly caused by atoms of the cathode material itself. Analysis of solutions has been performed using the flow discharge ion source. Lead and platinum were monitored at the ppb level in the urine of patients receiving cancer chemotherapy with the drug cis-platin. The data obtained support the idea that normally stored body lead is displaced by the platinum complexed in the drug, but only to a small extent. A novel investigation was made into the suitability of the technique for the analysis of organic species deposited on the cathode. The spectra of a wide variety of compounds are very similar to desorption chemical ionisation spectra. Although some sputtering does occur, the principal desorption process appears to be caused by rapid localised heating at the cathode surface.

APA, Harvard, Vancouver, ISO, and other styles

50

Whiteman, David James. "The physical chemistry of stabilising additives in rubber toughened polyolefins." Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285136.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Physical Chemistry'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles