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Jolly, Michael Matthew. "Method development in biological solid-state NMR." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/422129/.
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Solid-state nuclear magnetic resonance (ssNMR) has proved to be a useful tool in the analysis of structural and dynamic properties of proteins. However, the inherent low sensitivity of NMR hinders further advancements of the field. This thesis focuses on improving the sensitivity of ssNMR, be this through an improvement in signal to noise or an effective improvement in sensitivity by enhancing the information content. The mixed rotational and rotary resonance (MIRROR) sequence1 was employed to facilitate protein backbone assignment under moderate spinning speeds. Through the band selective nature of MIRROR, bidirectional transfer of magnetisation from the CCO site to the adjacent Cα and to the Cα of the next amino acid is possible. When applied to a 3D-NCOCA experiment this may be used to double the information content, providing correlations from CCO(i-1) to both Cα(i-1) and Cα(i). The MIRROR recoupling of CCO to Cα, is inherently low-power, allowing MIRROR to be utilised in a low-power experiment. Through this, greater enhancements in sensitivity per unit time can be realised. The longitudinal relaxation time (T1) limits the sensitivity per unit time at both room and cryogenic temperatures. To develop the use of relaxation agents for cryogenic NMR experiments, the room temperature relaxation properties and dynamics of the model protein, GB3, were explored. Site-specific relaxation measurements were used to understand the relaxation of residues in the protein and gain understanding into how this relates to the dynamics of the protein. In addition, low-temperature NMR measurements were used to investigate the effect temperature has on relaxation. The ongoing development of polarisation enhancement methods and machinery have made great progress in recent years particularly on the application towards biomolecules. However, arguably the most promising polarisation enhancement technique, dynamic nuclear polarisation (DNP) suffers from a variety of problems. Namely, line broadening effects as a result of the low-temperatures required and through doping with paramagnetic agents. Furthermore, the current method of sample preparation for DNP via the use of doping with exogenous radicals is not viable for all samples. Endogenous radicals for the DNP of large biomolecules may offer several advantages to their exogenous counterparts, including but not limited to, a greater understanding of quenching effects and polarisation transfer. This thesis explores the possibility of creating pseudo-biradicals bound covalently to a protein surface to elicit enhancements through the cross effect DNP mechanism. In summary, we have developed a range of methods that enhance the information content and sensitivity, which will provide new approaches for researchers investigating proteins using ssNMR.
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Asami, Sam. "Method development for biomolecular solid-state NMR spectroscopy." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2014. http://dx.doi.org/10.18452/17044.
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Im Rahmen der vorliegenden Arbeit, wird ein neuartiges Markierungsschema für die Festkörper-NMR-Spektroskopie vorgestellt, das sogenannte Reduced Adjoining Protonation (RAP) Schema, welches die Protonendetektion sämtlicher Aliphaten erlaubt. Hochaufgelöste, 1H-detektierte 1H,13C Korrelationsspektren wurden erhalten. Des Weiteren wurde der Vorteil von hohen MAS-Frequenzen untersucht. 1H- und 13C-detektierte 3D Zuordnungsexperimente wurden implementiert, welche uns die Zuordnung von 90% aller aliphatischen Resonanzen von alpha-Spektrin SH3 erlaubten. Da die chemische Verschiebung abhängt vom Strukturmotiv, kann sie verwendet werden, um Sekundärstruktur-Informationen abzuleiten. Darüber hinaus wurde ein 1H-detektiertes H(H)CH 3D Experiment entwickelt, um weitreichende 1H,1H Kontakte zu ermitteln, welche für die Bestimmung der Tertiärstruktur genutzt werden können. Um artefaktfreie Relaxationsdaten zu erhalten, wurde das RAP-Markierungsschema modifiziert, um 1H- und 13C-verdünnte Proben zu erhalten, in denen Spindiffusion unterdrückt ist. Für die Untersuchung von Sub-Mikrosekunden-Dynamik werden Experimente vorgestellt zur Bestimmung von 13C T1 Relaxationszeiten und 1H,13C dipolaren Kopplungstensoren für Rückgrat- und Seitenketten-Resonanzen. Des weiteren zeigen wir, dass das RAP-Markierungsschema auf nicht-kristalline Systeme, wie Amyloidfibrillen des Abeta1-40 Peptids der Alzheimer-Krankheit, angewendet werden kann. Unter Verwendung von 1H-Detektion, erhielten wir hochaufgelöste 1H,13C Korrelationsspektren. Schließlich wurde der Perdeuterierungsansatz auf den L7Ae-box C/D Protein-RNA Komplex aus P. furiosus angewendet. Wir erhielten hochaufgelöste, 1H-detektierte 1H,15N, sowie 13C,13C Korrelationsspektren des Protein-RNA Komplexes. Weiterhin haben wir eine Methode zur Bestimmung genauer Abstands- und Winkelinformationen für die Protein-RNA Schnittstelle etabliert und schlagen Ansätze vor, für die Zuordnung der chemischen Verschiebungen von RNA-Resonanzen.In this thesis, a novel labeling scheme for solid-state NMR spectroscopy, the Reduced Adjoining Protonation (RAP) scheme, is introduced, which allows proton detection of all aliphatic sites, as shown for the microcrystalline SH3 domain of alpha-spectrin. These samples yield high-resolution, 1H-detected 1H,13C correlation spectra. In addition, the benefit of high MAS frequencies was investigated. 1H- and 13C-detected 3D assignment experiments are implemented, which allowed us to assign 90% of all aliphatic resonances of alpha-spectrin SH3. As the chemical shift is dependent on the structural motif, it can be employed to derive secondary structure information. Furthermore, a 1H-detected H(H)CH 3D experiment is introduced, to obtain long-range 1H,1H contacts, which can be used for the determination of the tertiary structure. To obtain artifact-free relaxation data, the RAP labeling scheme was modified to obtain sparsely proton labeled, 13C dilute samples, in which spin diffusion is suppressed. To probe sub-microsecond dynamics, we report experiments to determine 13C T1 relaxation times and 1H,13C dipolar coupling tensors for backbone and side chain resonances, respectively. Furthermore, we show, that the RAP labeling scheme can be applied to non-crystalline systems, such as amyloid fibrils of the Alzheimer’s disease peptide Abeta1-40. Using 1H-detection, we obtained high-resolution 1H,13C correlation spectra. Finally, we applied the perdeuteration approach to the L7Ae-box C/D protein-RNA complex from P. furiosus. We obtained high-resolution, 1H-detected 1H,15N, as well as 13C,13C correlation spectra of the protein-RNA complex. In addition, we established a methodology to determine accurate distance and angular restraints for the protein-RNA interface and propose approaches for the chemical shift assignment of RNA resonances.
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Michaud-Rioux, Vincent. "Real space DFT by locally optimal block preconditioned conjugate gradient method." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110628.
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In condensed matter physics, atomistic first principle calculations are often necessary to achieve a microscopic understanding of the observed experimental phenomena and to make quantitative predictions of physical properties. In practice, atomic scale systems have irregularities (e.g. surface roughness) or defects (e.g. substitutional atoms or vacancies) that are too strong to be ignored or treated as small perturbations. In this thesis, we report the development of a real space DFT code for studying atomic scale systems from first principles. Our code, named MatRcal, which stands for "Matlab-based real space calculator", is developed in the technical computing language Matlab. The physics is described by density functional theory. The method itself is based on projecting the Kohn-Sham Hamiltonian on a uniform Cartesian grid. High-order finite-differencing is used to discretize the Laplacian operator. The potential due to the atomic nuclei is approximated with ab initio pseudopotentials. The pseudopotentials are generated following the procedure proposed by Troullier and Martins. We use the fully separable form introduced by Kleinman and Bylander. We argue that the method is simpler and yet has many advantages compared with conventional spectral methods. We provide relevant mathematical techniques and implementation details. In particular, we present and compare different eigensolvers used to diagonalize the Kohn-Sham Hamiltonian. We validate our software by comparing the HOMO-LUMO gaps of many organic and inorganic molecules obtained using our method with those obtained with the commercial code Gaussian. Our results are in excellent agreement. Our method gains in computational speed and algorithm parallelism, and its power in handling real space boundary conditions will be a major advantage for future applications in nanoelectronic device modelling.En physique de la matière condensée, les calculs numériques sont souvent nécessaires pour parvenir à comprendre les phénomènes microscopiques observés lors d'expériences ou à prédire quantitativement des propriétés physiques. En pratique, les systèmes d'échelle atomique sont irréguliers (rugosité de surface) ou comportent des défauts (atomes de substitution ou lacunes), ce qui induit des effets trop sévères pour être ignorés ou traités comme des perturbations. Dans cette thèse, nous présentons une méthode qui permet d'étudier des systèmes d'échelle atomique à partir des lois fondamentales de la physique. Notre logiciel, nommé MatRcal, qui signifie "Matlab-based real space calculator", est développé dans le langage Matlab. La physique est décrite par la théorie de la fonctionnelle de la densité. La méthode projette l'Hamiltonien de Kohn-Sham sur un maillage Cartésien uniforme. Le calcul des différences finies est utilisé pour discrétiser l'opérateur Laplacien. Le potentiel dû aux noyaux atomiques est approximé par des pseudopotentiels non-empiriques. Les pseudopotentiels sont générés en suivant la procédure proposée par Troullier et Martins. Nous utilisons la forme séparable introduite par Kleinman et Bylander. Nous soutenons que la méthode est plus simple et pourtant présente de nombreux avantages par rapport aux conventionnelles méthodes spectrales. Nous introduisons plusieurs techniques mathématiques pertinentes à notre étude et certains détails d'implémentation. Entre autres, nous présentons et comparons plusieurs algorithmes de calcul de vecteurs propres utilisés pour diagonaliser l'Hamiltonien de Kohn-Sham. Nous validons notre méthode en comparant la largeur de bande interdite "HOMO-LUMO" de nombreuses molécules organiques et inorganiques prédites par notre méthode avec celles prédites par le logiciel commercial Gaussian. Notre méthode permet des gains en rapidité et en parallélisme, mais la possibilité de traiter des conditions limites non-périodiques sera le principal atout pour de futures simulations de dispositifs nanoélectroniques.
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Huq, Syed Ejazul. "Thin film deposition by the ionized cluster beam method." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304288.
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Silver, Mark. "Application of the pseudopotential method to the theory of semiconductors." Thesis, University of Surrey, 1991. http://epubs.surrey.ac.uk/2988/.
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El-Badawy, Z. I. "Organic films deposited by the Langmuir-Blodgett method and by adsorption." Thesis, Lancaster University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374634.
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Anderez, Dora M. Gomez. "A study of the synchrotron Laue method for quantitative crystal structure analysis." Thesis, University of York, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238717.
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Williams, Joshua R. "Fundamental investigations of skutterudite phase formation by the modulated elemental reactant method /." view abstract or download file of text, 2002. http://wwwlib.umi.com/cr/uoregon/fullcit?p3055721.
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Thesis (Ph. D.)--University of Oregon, 2002.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 124-128). Also available for download via the World Wide Web; free to University of Oregon users.
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Yamada, Takashi. "Basic properties of Dual Reciprocity Boundary Element Method and applications to magnetic field analysis." Thesis, University of Portsmouth, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240420.
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Randhawa, Banljinder Singh. "Electromagnetic modelling of curved structures using a hybrid finite-volume finite-difference time-domain method." Thesis, University of York, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362043.
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Grainger, David S. "The application of the maximum entropy method to one- and two-dimensional nuclear magnetic resonance spectroscopy." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291092.
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Wellington, Joseph Paul William. "Applications of the periodic electrostatic embedded cluster method to solid state actinide chemistry." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/1571738/.
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The work described in this thesis uses density functional theory (DFT) with an embedded cluster method, known as the periodic electrostatic embedded cluster method (PEECM) to study solid state actinide systems. The theoretical background of electronic structure calculations is discussed in the first chapter, while the remaining chapters deal with results of the studies. In Chapter 2 the PEECM is used to include long-range electrostatic interactions in calculations of Quantum Theory of Atoms in Molecules (QTAIM) bond critical point and delocalisation index metrics for the actinide-element bonds in Cs2UO2Cl4, U(Se2PPh2)4 and Np(Se2PPh2)4. The effects of the environment are seen to be minor, suggesting they do not account for the differences previously observed between the experimental and theoretical QTAIM data. In Chapter 3 the electronic structure of actinide dioxide systems has been investigated by examining the projected density of states (PDOS). While PBE incorrectly predicts these systems to be metallic, PBE0 finds them to be insulators, with the composition of the valence and conduction levels agreeing well with experiment. In Chapter 4 molecular and dissociative water adsorption on the (111) and (110) surfaces of UO2 and PuO2 has been investigated, with that on the (110) surface being stronger than on the (111). Similar energies are found for molecular and dissociative adsorption on the (111) surfaces, while on the (110) there is a clear preference for dissociative adsorption. Adsorption energies and geometries on the (111) surface of UO2 are in good agreement with recent periodic DFT studies using the GGA+U approach. In Chapter 5 oxygen vacancies are investigated on the actinide oxide surfaces. Oxygen vacancy formation energies are found to be much greater on UO2 than PuO2 surfaces. Oxygen vacancies lead to a preference for dissociative adsorption of water on both the (111) and (110) surfaces, with adsorption energies being much greater on PuO2 than UO2 surfaces.
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Pang, King-Hung Geoffrey. "Absolute measurement of the lattice parameter of perfect diamonds of known nitrogen content by the divergent beam (Kossel) X-ray method." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319399.
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Chen, Rung-Sheng. "The bend and polish method of aspheric surface manufacture : an investigation into optical design for this process and into the process itself." Thesis, Imperial College London, 2001. http://hdl.handle.net/10044/1/8158.
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Asami, Sam [Verfasser], Bernd [Akademischer Betreuer] Reif, Andreas [Akademischer Betreuer] Möglich, and Hartmut [Akademischer Betreuer] Oschkinat. "Method development for biomolecular solid-state NMR spectroscopy : accessing structure and dynamics of biomolecules in the solid-state / Sam Asami. Gutachter: Bernd Reif ; Andreas Möglich ; Hartmut Oschkinat." Berlin : Humboldt Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2014. http://d-nb.info/1060425262/34.
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Asami, Sam [Verfasser], Bernd Akademischer Betreuer] Reif, Andreas [Akademischer Betreuer] Möglich, and Hartmut [Akademischer Betreuer] [Oschkinat. "Method development for biomolecular solid-state NMR spectroscopy : accessing structure and dynamics of biomolecules in the solid-state / Sam Asami. Gutachter: Bernd Reif ; Andreas Möglich ; Hartmut Oschkinat." Berlin : Humboldt Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2014. http://nbn-resolving.de/urn:nbn:de:kobv:11-100220957.
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Bennett, Patrick M. "Solid State Fermentation in a Spouted Bed Reactor and Modelling Thereof." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1384774243.
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Borghi, Giovanni. "Gutzwiller approximation applied to inhomogeneous lattice models and solid-state systems." Doctoral thesis, SISSA, 2011. http://hdl.handle.net/20.500.11767/4290.
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The plan of this thesis is as follows. Chapt. 1 is devoted to the explanation of the main theoretical tool of our work, namely the GVM and GA. After introducing their earliest formulation by Martin C. Gutzwiller, we discuss their effectiveness in describing the physics of strongly correlated conductors, emphasizing the improvements they bring in comparison with mean-field, independent-electron approximations such as HF, and their limitations with respect to more refined, though computationally more costly, methods like DMFT and VQMC. We mention how the GA was initially exploited as an approximate tool for analytical calculation of expectation values on the GVW, and how later studies proved its exactness in the limit of infinite lattice coordination. After that, we discuss its more recent multi-band formulation which, together with the mixed-basis parametrization of Gutzwiller parameter matrix, is particularly important for combining the GVM with DFT.
In Chapt. 2 we present our results for the strongly correlated Hubbard lattice with broken translational invariance due to the presence of a surface (panel (a) in Fig. 1), a metal-metal or metal-insulator junction (panel (b)), or a “sandwich” of Mott insulator or strongly correlated metal between metallic leads (panel (c)). For all geometries, we show the layer dependence of the quasi-particle weight and provide approximate analytical fits for the data, together with a comparison with DMFT calculations on similar systems.
In Chapt. 3, we introduce the formalism of DFT, the Kohn-Sham self-consistent
equations for the functional minimization and the LDA for exchange and correlation functionals. We further discuss the performance and limitations of LDA and present the LDA+U method as a way to correct the self-interaction error of LDA. We explain the details of the GDF in Chapt. 4, and underline its similarities and differences with respect to the LDA+U functional. In the same chapter we present our data for paramagnetic and ferromagnetic bcc iron obtained through our implementation of LDA+G in the Siesta code. We show energy differences between spin-polarized and unpolarized Iron computed within LDA, GGA and LDA+G and with different basis sets. We compare the band structure, lattice parameters and magnetic moments (some sample data is shown in Table 1) obtained with these functionals, and discuss the implications of our results on the understanding of the origin of magnetism in
transition metals.
In the appendices we list some important results that we believed too detailed or too marginal to be presented in the main body of the thesis. Appendix A is devoted to some proofs and detailed explanations related to the GVM. In Appendix B we include all details related to the calculations on the layered geometries of Chapt. 2.
In Appendix C we explain how to implement spin and orbital symmetries in the
parametrization of the Gutzwiller projector, while in Appendix D we give the details of the minimization algorithm we implemented for optimizing the variational energy of the LDA+G calculation with respect to Gutzwiller parameters. Finally, Appendix E contains various topics of DFT and LDA+U that are important for the understanding of the GDF we implemented and discussed in Chapt. 4.
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SANTOS, IVANILDO A. dos. "Estudo das soluções sólidas de LiGdsub(1-x)Lusub(x)Fsub(4) visando o crescimento de cristais." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11656.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN/CNEN-SP
FAPESP:05/57580-2
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So, Biu 1959. "THE METHODOLOGY AND IMPLEMENTATION OF RELAXATION METHOD TO INVESTIGATE ELECTRO-THERMAL INTERACTIONS IN SOLID-STATE INTEGRATED CIRCUITS." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276384.
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Lechner, Ruep Ekkehard, Goetz Schuck, and Klaus Langer. "Mechanism of proton conduction in solid-state protonic conductors: method and results from investigations by QENS techniques." Diffusion fundamentals 12 (2010) 3, 2010. https://ul.qucosa.de/id/qucosa%3A13865.
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Biswal, Mamata. "Determination and first principles calculations, using the PAW/GIPAW method, of NMR parameters in inorganic fluorides." Phd thesis, Université du Maine, 2013. http://tel.archives-ouvertes.fr/tel-01015856.
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This thesis focuses on the determination and the modeling, by the PAW/GIPAW (Gauge Including Projector Augmented Waves) method, of NMR parameters in inorganic fluorides. In the first part, a correlation between experimental 19F isotropic chemical shift (diso) and calculated 19F isotropic shieldings (siso) of binary fluorides with obvious assignments is established that allows to predict 19F NMR spectra with a good accuracy. The quadrupolar parameters of these fluorides are also determined and calculated. In the second part, a complete and unambiguous assignment of the 19F NMR lines of NbF5 and TaF5 is obtained, ensured by the linearity between experimental 19F diso values and calculated 19F siso values. On the other hand, for the studied MF4 (b-ZrF4, HfF4, CeF4, ThF4) compounds, characterized by smaller 19F diso ranges, except for ThF4, the poor correlations between experimental 19F diso and calculated 19F siso values prevent us to propose an assignment of the 19F NMR lines. In the last part, NaAsF6 and KPF6, exhibiting large 19F-X 1J-coupling and phase transitions at temperatures close to room temperature (RT) are investigated by DTA or DSC and variable temperature X-ray powder diffraction and multinuclear solid-state NMR. The structures of a- and b-NaAsF6 are determined. KPF6 adopts a disordered high symmetry structure at RT. Unfortunately, attempts to determine the atomic positions of the two first low temperature phases remain unsuccessful. This work highlights the potentialities and some limitations of this method as well as the care that must be taken when dealing with optimized structures.
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Esters, Marco. "Experimental and Computational Investigations of Kinetically Stable Selenides Synthesized by the Modulated Elemental Reactants Method." Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23175.
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The controlled and targeted synthesis of new solid materials is still a challenge difficult to overcome. Slow diffusion rates and long diffusion lengths require long reaction times and high synthesis temperatures, resulting in limited control over the reaction pathway. The Modulated Elemental Reactants (MER) method uses compositionally modulated precursors with atomically thin elemental layers that form amorphous alloys upon annealing while maintaining composition modulation. In this amorphous intermediate, nucleation, not diffusion, control the formation of the product, enabling kinetic control of the reaction, and the synthesis of new metastable compounds, heterostructures with designed nanoarchitecture, and thin films with a high degree of texturing.
This dissertation uses experimental and computational methods to investigate compounds synthesized by the MER method. Firth, the MER method is used to synthesize ferromagnetic CuCr2Se4 films that show a large degree of crystallographic alignment and interesting magnetic properties such as temperature-dependent easy axes and negative magnetoresistivity.
The second part investigates ferecrystals, rotationally disordered members of the misfit layer compounds family. The MER method’s ability to control the nanoarchitecture of the products is used to synthesize a new type of structural isomers, allowing for the synthesis of thousands of ternary compounds using the same elements. Experimental methods are also used to monitor the formation of ferecrystalline compounds using [(SnSe)1+δ][VSe2] as a model system.
Despite the vast number of compounds available, however, explaining the properties and stability of ferecrystals is still in its infancy. In the last part of this dissertation, ab initio methods are employed to investigate the components in our ferecrystals. Specifically, isolated layers of VSe2 with its structural distortions due to a charge density wave, SnSe with its thickness-dependent structures, and BiSe with its flexible lattice and anti-phase boundaries are investigated to complement experimental results. Some properties, such as the structural distortion in VSe2 and the different stabilities of BiSe layers, can be explained very well using this simplified model, but others, such as the structure of SnSe layers, are not exclusively determined by their dimensionality, underlining the complex nature of the interactions in ferecrystals.
This dissertation includes previously published and unpublished co-authored material.
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FERRARI, MARCO A. "Laser de Nd:YLF para aplicacoes em lidas." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11745.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Nomura, Kaoru. "Development of a Selective Homonuclear Dipolar Recoupling Method in Magic-Angle Spinning Solid-State NMR and Its Application to the Structural Analysis of a Molicule." 京都大学 (Kyoto University), 1999. http://hdl.handle.net/2433/181980.
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Junior, Nelson Alves. "Efeitos da desordem do campo cristalino sobre as fases moduladas de um modelo magnético." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-09122013-094058/.
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Nesta tese realizamos um estudo de campo médio dos efeitos da desordem do campo cristalino sobre os diagramas de fases do modelo ANNNI com spin 1. Resultados de campo médio anteriores obtidos para o modelo com campo cristalino constante mostraram fases parcialmente desordenada em seus diagramas de fases. No entanto, a existência de tais fases não é garantida, devido às flutuações não levadas em conta na aproximação de campo médio. Sendo assim, estudamos o modelo com campo cristalino constante por meio de simulações de Monte Carlo. Nosso objetivo foi fornecer maior credibilidade aos resultados de campo médio obtidos anteriormente, e com isso adquirirmos maior confiança nos resultados de campo médio apresentados nesta tese para um campo cristalino aleatório. Os resultados das simulações mostraram evidências de que a configuração com planos desordenados da fase comensurável de período 6, observada em baixas temperaturas, pode sofrer uma transição interna para uma configuração na qual tais planos estão ausentes. Esse resultado está em concordância com os estudos de campo médio. Para o caso de um campo cristalino aleatório, investigamos os diagramas de fases do modelo na aproximação de campo médio. Para uma distribuição de probabilidades genérica do campo cristalino, obtivemos o funcional da energia livre e as equações de campo médio, assim como as expressões das linhas críticas e dos pontos tricríticos do modelo. Para investigarmos os efeitos da desordem sobre os diagramas de fases, consideramos as distribuições de probabilidade do campo cristalino delta-bimodal e gaussiana.In this thesis we present a mean-field study of the effects of the disorder of the single-ion anisotropy on the phase diagrams of the spin-l ANNNI model. Previous mean-field results for the model with constant single-ion anisotropy showed partially disordered phases in the phase diagrams of the model. H owever , the existence of such phases cannot be taken as granted, due to the fiuctuations not taken into account in the mean-field approximation. Thus, we studied the model with constant single-ion anisotropy by means of Monte Carlo simulations. Qur aim was to give credit to previous mean-field results and to get more confidence in the mean-field results showed in this thesis obtained for a random single-ion anisotropy. The results obtained from the simulations showed evidences that the configuration of the commensurate phase with period 6 displaying disordered planes, found at low temperatures, may undergo an internaI phase transition to a phase in which such planes are absent. This result is in agreement with previous mean-field studies. For a random single-ion anisotropy, we investigated the phase diagrams of the model within mean-field approximation. For a generic probability distribution of the anisotropy, we obtained the free-energy functional and the mean-field equations, as well as the expressions for the criticallines and tricritical points of the model. In order to investigate disorder effects, we obtained phase diagrams of the model by considering a double-delta and a Gaussian probability distribution of the single-ion anisotropy.
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Elbagerma, Mohamed A. "Analytical method development for structural studies of pharmaceutical and related materials in solution and solid state : an investigation of the solid forms and mechanisms of formation of cocrystal systems using vibrational spectroscopic and X-ray diffraction techniques." Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/4467.
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Analysis of the molecular speciation of organic compounds in solution is essential for the understanding of ionic complexation. The Raman spectroscopic technique was chosen for this purpose because it allows the identification of compounds in different states and it can give information about the molecular geometry from the analysis of the vibrational spectra. In this research the ionisation steps of relevant pharmaceutical material have been studied by means of potentiometry coupled with Raman spectroscopy; the protonation and deprotonation behaviour of the molecules were studied in different pH regions. The abundance of the different species in the Raman spectra of aqueous salicylic acid, paracetamol, citric acid and salicylaldoxime have been identified, characterised and confirmed by numerical treatment of the observed spectral data using a multiwavelength curve-fitting program. The non-destructive nature of the Raman spectroscopic technique and the success of the application of the multiwavelength curve-fitting program demonstrated in this work have offered a new dimension for the rapid identification and characterisation of pharmaceuticals in solution and have indicated the direction of further research. The work also covers the formation of novel cocrystal systems with pharmaceutically relevant materials. The existence of new cocrystals of salicylic acid-nicotinic acid, DLphenylalanine , 6-hydroxynicotinic acid, and 3,4-dihydroxybenzoic acid with oxalic acid have been identified from stoichiometric mixtures using combined techniques of Raman spectroscopy (dispersive and transmission TRS), X-ray powder diffraction and thermal analysis. Raman spectroscopy has been used to demonstrate a number of important aspects regarding the nature of the molecular interactions in the cocrystal. Cocrystals of salicylic acid - benzamide, citric acid-paracetamol and citric acid -benzamide have been identified with similar analytical approaches and structurally characterised in detail with single crystal X-ray diffraction. From these studies the high selectivity and direct micro sampling of Raman spectroscopy make it possible to identify spectral contributions from each chemical constituent by a peak wavenumber comparison of single-component spectra (API and guest individually) and the two- component sample material (API/guest), thus allowing a direct assessment of cocrystal formation to be made. Correlation of information from Raman spectra have been made to the X-ray diffraction and thermal analysis results. Transmission Raman Spectroscopy has been applied to the study cocrystals for the first time. Identification of new phases of analysis of the low wavenumber Raman bands is demonstrated to be a key advantage of the TRS technique.
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Salas-Illanes, Nora. "Electronic Structure of Selected Materials by Means of the QSGW Method within the LAPW+LO Framework." Doctoral thesis, Humboldt-Universität zu Berlin, 2019. http://dx.doi.org/10.18452/19804.
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Materialien formen die moderne Welt: Sie umgeben uns in unserem alltäglichen Leben.
Unser Ziel ist die Materialeigenschaften nach unseren Bedürfnissen maßzuschneidern. Viele Materialeigenschaften wie Bandücken und Elektronendichteverteilung werden durch elektronische Zustände bestimmt.
Die meisten Vorhersagen in Bezug auf Materialien entstammen der Dichtefunktionaltheorie (DFT). Diese Theorie ermittelt Grundzustandseigenschaften und kann jedoch keine Energien von angeregten Zuständen liefern. Um angeregte Zusände zu beschreiben, bedarf es daher einer höherstufigen Theorie: die Vielteilchen-Störungstheorie (MBPT) . Im Rahmen von MBPT ist das üblichste Verfahren die GW-Näherung (GWA), worin Elektronen als Quasiteilchen (QP) beschrieben werden. Der Energieunterschied zwischen einem nicht-wechselwirkenden Teilchen und einem QP ist die Selbstenergie. In GWA ergibt sich die Selbsenergie als Produkt aus die Einteilchen-Greenfunktion, G, und die abgeschirmte Coulomb-Wechselwirkung, W, und führt zu der wahren Anregungsenergie von QP.
Diese Doktorarbeit beinhaltet die Implementierung von selbstkonsistentem Quasiteilchen-GW (QSGW) im exciting Code. Dieses Software-Paket benutzt die Linearized-Augmented-Plane-Wave-Methode (LAPW), welche alle Elektronen gleichberechtigt behandelt. Beginnend mit DFT optimiert die QSGW-Methode den Einteilchen-Hamiltonoperator durch eine selbstkonsistente Suche eines optimierten Austausch-Korrelationspotentials. Am Ende des iterativen Prozesses liefert die QSGW-Methode Eigenfunktionen und Eigenwerte der QP. Wir präsentieren mit QSGW ermittelte elektronische Strukturen von neun kristallinen Festkörpern. Wir präsentieren die zugehörigen Bandstrukturen und Zustandsdichtediagramme und vergleichen anhand dieser die QSGW-Ergebnisse mit Ergebnissen von DFT und G0W0. Zusätzlich untersuchen wir die elektronische Ladungsdichte und Wellenfunktion in ausgewählten Materialien.Materials shape the modern world: they appear everywhere in our daily life. We investigate what governs the material's properties, in order to tailor them to meet our needs. Properties, e.g., bandgaps, and electronic density distribution are determined by the electronic structure. Most predictions on materials follow from computational physics, in particular density-functional theory (DFT). This scheme returns ground-state properties, but it fails to provide excited-state energies. To find the latter, we have to recourse to a higher degree of theory, namely many-body perturbation theory (MBPT). Within MBPT, the most popular framework is the GW approximation (GWA) which describes electrons as quasiparticles (QP). The difference in energy between a non-interacting particle and a QP is called the self-energy. In GWA, the product of the Green function G and W, the screened Coulomb interaction, returns the self-energy. GWA is in principle self-consistent, but is mostly implemented as a perturbative correction to DFT results, known as G0W0. Unfortunately, the electronic structure given by G0W0 depends on the initial DFT results. This PhD project consists in the implementation of the self-consistent quasiparticle GW (QSGW) in the exciting code. This software package uses the all-electron linearized augmented planewave (LAPW) method, treating every electron on equal footing. Starting from DFT, the QSGW method (based in the GWA) optimizes the one-particle Hamiltonian through a self-consistent search for an optimized exchange-correlation potential. At the end of the iterative process, the QSGW method provides eigenfunctions and eigenvalues of the QPs. Considering nine crystalline solids, we present their electronic structure by means of QSGW. We present the bandstructures and density of state diagrams, comparing QSGW results to DFT and G0W0 results. In addition, we study the electronic charge density and wavefunction in selected materials.
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Bos, Cornelis [Verfasser]. "Atomistic simulation of interface controlled solid-state phase transformations : development and application of a multi-lattice kinetic Monte Carlo method / Institut für Metallkunde der Universität Stuttgartt ... Vorgelegt von Cornelis Bos." Stuttgart : Max-Planck-Inst. für Metallforschung, 2006. http://d-nb.info/979722705/34.
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Beyer, Frank R. "Hauptspannungstrajektorien in der numerischen Festkörpermechanik." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-178497.
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Für die anschauliche Darstellung der Ergebnisse mechanischer Untersuchungen von Bauteilbeanspruchungen existieren diverse Visualisierungsformen. Eine solche Visualisierungsform ist die Darstellung von Hauptspannungstrajektorien, vorwiegend der Hauptnormalspannungstrajektorien des Spannungszustandes eines Bauteils. Trajektorienbilder sind im Bereich des Bauingenieurwesens insbesondere im Massivbau nach wie vor von großem Interesse. So werden beispielsweise die in der Stahlbetonnormung fest verankerten Stabwerkmodelle in erster Linie auf der Basis von Hauptspannungstrajektorien entwickelt. Aus diesem Grund gehören Trajektorienbilder heute nicht nur zum akademischen Standardlehrstoff, sondern werden auch in wissenschaftlichen Veröffentlichungen gern zur Erläuterung von komplexen Spannungszuständen herangezogen. Unglücklicherweise finden sich in der einschlägigen Fachliteratur und in wissenschaftlichen Arbeiten nicht selten grundlegende Fehldarstellungen. Diese Arbeit stellt einen geeigneten Algorithmus zur korrekten Darstellung von Trajektorienbildern auf der Basis numerisch (beispielsweise mit der Finite-Elemente-Methode) berechneter Spannungslösungen bereit. Anhand von systematischen Untersuchungen zu verschiedenen Bauteilgeometrien und Beanspruchungs-konstellationen konnte eine Reihe von immer wieder zu findenden Fehlinterpretationen von Trajektorienbildern aufgezeigt werden. Die oft angenommene Analogie von Spannungstrajektorien zu Stromlinien von Fluidströmungen im Sinne eines „Kraftflusses“ wurde widerlegt. Das Problem bei herkömmlichen Trajektorienbildern, dass diese nicht imstande sind, Auskunft über die Größe der Spannungen zu geben, führte mitunter zu der bisweilen verbreiteten Annahme, die Verdichtung von Trajektorien in einem Trajektorienbild bedeute eine Spannungskonzentration an entsprechender Stelle. Anhand von Beispielen wird dies eindeutig widerlegt. Zur Vermeidung dieses Fehleindrucks wurde eine neue Darstellungsform eingeführt, die neben den Richtungen auch die Größen der Hauptspannungen anhand eines Farbmaßstabes ablesbar macht. Mithilfe einer variablen Schrittweitensteuerung konnte die Genauigkeit bei der Pfadverfolgung der Trajektorien gegenüber festen Schrittweiten maßgeblich verbessert werden. Geeignete Abbruchkriterien gewährleisten das zuverlässige Auffinden von äußeren sowie innenliegenden Bauteilbegrenzungen und die Detektion geschlossener Trajektorien. Einen wesentlichen Punkt stellen mögliche Singularitäten wie isotrope Punkte, isotrope Grenzen oder isotrope Gebiete dar, in denen die Hauptspannungsrichtungen mithilfe der Lösung des Eigenwertproblems nicht eindeutig ermittelbar sind. Deren Nichtbeachtung ist eine wesentliche Ursache für Fehldarstellungen in der Literatur. Die an solchen Stellen auftretenden Effekte und entstehenden Probleme bei der Ermittlung und Interpretierbarkeit von Trajektorienbildern wurden systematisch analysiert und entsprechende Lösungsvorschläge erarbeitet. Bisher blieb die Verwendung von Trajektorienbildern praktisch auf zweidimensionale Probleme beschränkt. Das Potenzial von Spannungstrajektorien zur Visualisierung dreidimensionaler Spannungszustände war bislang noch unerforscht. Daher wurde das Verfahren zur Berechnung von Spannungstrajektorien auf dreidimensionale Spannungszustände übertragen. Während sich einige Teilbereiche des entwickelten Algorithmus, wie beispielsweise die Schrittweitensteuerung, problemlos unter Hinzuziehung einer weiteren Richtungskomponente für dreidimensionale Probleme erweitern lassen, hat sich gezeigt, dass diese Erweiterung auch diverse Nichttrivialitäten enthält. Bei den aus der Berechnung erhaltenen Trajektorien handelt es sich im dreidimensionalen Fall um räumliche Kurven. Eine wesentliche Erkenntnis aus berechneten dreidimensionalen Trajektorienbildern ist, dass sich diese Raumkurven im Unterschied zum ebenen Fall in der Regel nicht schneiden und somit keine Maschen zwischen den Trajektorien wie im Zweidimensionalen aufspannen. Eine noch verbleibende Schwierigkeit bei der Anwendung dreidimensionaler Trajektorienbilder besteht in deren interpretierbarer Darstellung. In der vorliegenden Arbeit wurden hierzu einige Vorschläge erarbeitet sowie deren Anwendbarkeit getestet und bewertet. Um die Möglichkeit der eigenständigen Berechnung von Trajektorienbildern einem breiten Nutzerkreis zugänglich zu machen, können aufbauend auf den Erkenntnissen dieser Arbeit leicht bedienbare Softwarelösungen mit grafischer Benutzeroberfläche entwickelt werden. Der Algorithmus zur Trajektorienermittlung wurde mit diesem Ansinnen in allen Details beschrieben. Auf dem Gebiet der Trajektorien dreidimensionaler Spannungszustände hat sich darüber hinaus noch weiterer Forschungsbedarf herausgestellt, hierzu werden in der Arbeit an den entsprechenden Stellen einige Vorschläge zur Weiterentwicklung gemacht. Der entwickelte Algorithmus ermöglicht darüber hinaus auch direkt auch die Ermittlung von Trajektorien materiell oder geometrisch nichtlinearer sowie dynamischer und sonstiger Probleme, sofern der entsprechende Spannungszustand vorliegt. Außerdem kann der Algorithmus prinzipiell auch zur Bestimmung von Hauptschubspannungstrajektorien oder Hauptmomentenlinien angewandt werdenThere are several kinds of visualisation for the illustration of the results of mechanical investigations of structural elements’ load bearing behaviour. The illustration of the stress state via principal stress trajectories, mainly principal normal stress trajectories, is one of them. In the field of civil engineering, trajectory plots are still of notable interest, particularly in solid construction. Thus, the truss models as part of the European engineering standards for steel-reinforced concrete are primarily developed using principal stress trajectories. For this reason, trajectory plots are not only part of the academic subjects taught at university, but they are also used in scientific publications for the illustration of complex stress states. Unfortunately, fundamental misrepresentations are not rare in the relevant literature and scientific works. This work provides a suitable algorithm for accurate trajectory plots based on numerically computed stress solutions (e.g. using the finite element method). By means of systematic investigations of several structural element’s geometries and loading situations, a number of prevalent misinterpretations was identified. The analogy often assumed between stress trajectories and streamlines of fluid flow in terms of “load flow” has been disproved. A property of traditional trajectory plots is not able to indicate the level of stress. Thus, in areas of narrowing trajectories stress concentrations are often assumed. By means of examples this assumption was clearly disproved. To prevent the appearance of such misimpressions, the stress levels are represented using a colour scale known from contour plots. An adaptive incrementation during path tracing allows a significant increase of accuracy compared with uniform incrementation. Suitable stop criteria ensure reliable detection of outer and inner borders as well as closing of trajectories. One important aspect is the appearance of singularities like isotropic points, isotropic borders and isotropic areas, where the principal stress directions in terms of eigenvectors are not unique. Non-observance is one of the main causes of misrepresentations of trajectory plots in literature. The effects due to the appearance of isotropic points and the arising problems for calculation and interpretation of stress trajectories were systematically analysed, and proposals for a solution were made. Up to now, the usage of trajectory plots was limited to two-dimensional problems. The potential of stress trajectories for the visualisation of three-dimensional stress states was still unexplored. Therefore, the algorithm for the calculation of stress trajectories was augmented in three dimensions. Some parts of the two-dimensional algorithm like adaptive incrementation could be directly translated simply considering the third coordinate, whereas the necessary modifications of some parts turned out to be non-trivial. The stress trajectories of three-dimensional stress states prove to be space curves. An essential finding from the calculated three-dimensional trajectory plots was, that three-dimensional trajectories – compared to two-dimensional trajectories – generally do not intersect each other. According to this, three-dimensional trajectories generally do not build meshes. The interpretable display of three-dimensional trajectories is still a difficulty. In this work, the applicability of some methods has been tested and assessed. To enable a large group of users to create stress trajectory plots individually, easily operated software solutions with a graphical user interface should be developed. For this purpose, the developed algorithm for tracing trajectories is described in every detail. In the field of three-dimensional stress trajectories need of further research came to light, which is specified in the corresponding parts of this work. In addition, the developed algorithm allows also the calculation of stress trajectories of geometrical and material non-linear as well as dynamic and other problems, if only the stress state is available. Furthermore, the algorithm can be applied for the calculation of principal shear stress trajectories and principal moment trajectories
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Bennett, David Alexander. "Structural methods in solid-state NMR." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13242/.
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New solid-state NMR experiments for measuring internuclear distances are designed using symmetry principles. The “recoupling” sequences described here are intended to reintroduce the MAS-averaged heteronuclear dipole-dipole coupling between a spin-1/2 nucleus (e.g. 1H) and a half-integer quadrupolar nucleus (e.g. 17O, I = 5/2). The magnitude of the dipolar interaction depends on the separation between the coupled nuclei, so the evolution of the spin system under the recoupled Hamiltonian can be used to measure the internuclear distance. Simulations of the spin dynamics are used initially to select candidate sequences and these are subsequently employed to measure both long-range and direct O–H distances in powdered L-Tyrosine.HCl (isotopically enriched with 17O at 20%to 30% at the O$^\eta$ site). Improvements to existing methods for the data analysis for this type of NMR experiment are also discussed, including the restriction and/or removal of certain fit parameters and the explicit inclusion of inhomogeneous radio-frequency fields as part of the fitting procedure. The effects of processing on the uncertainty of experimentally determined distances are considered, and a new analysis method which circumvents several of these effects is presented. Similar recoupling sequences can be used to measure the anisotropy of proton chemical shifts, and some preliminary results are also presented for this application. A systematic method for the assignment of congested spin-1/2 spectra resulting from molecules with large numbers of chemically similar sites is also described. This makes use of a comparison between the chemical shift tensor measured as usual by the 2D-PASS experiment and its principal components calculated from first principles using the density functional theory package CASTEP. The initial peak assignment is generated randomly and then varied using a steepest-ascent hill climbing algorithm with the square sum of the difference between the experimental and calculated principal values of the chemical shift tensor as the target function. The new method is tested on the 13C spectrum of the anti-inflammatory drug flufenamic acid and found to be superior to simple assignments using only the isotropic chemical shift.
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Arzakantsyan, Mikayel. "Yb:YAG Laser Crystals with Controlled Doping Distribution." Phd thesis, Ecole Polytechnique X, 2013. http://pastel.archives-ouvertes.fr/pastel-00879616.
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Le développement de lasers solides de puissance-moyenne élevée doit faire face à des problèmes très spécifiques. La gestion de la thermique et de l'amplification de l'émission spontanée (ASE) pour de larges amplificateurs lasers deviennent des points clés lorsque l'augmentation de l'énergie de vient conséquente. Lucia est une chaîne laser de forte puissance moyenne qui repose sur le concept du miroir actif avec un cristal ou une céramique d'Yb:YAG comme milieu à gain. Comme pour d'autres systèmes lasers comparables, la distribution des ions actifs du milieu à gain est homogène en volume. Un profil variable du taux de dopage présente des avantages significatifs en termes de gain et par conséquent ouvre le chemin à une minimisation efficace des effets délétères de l'ASE et de l'échauffement. Cette thèse concerne la fabrication de tels milieux à gain. La méthode de croissance cristalline Bagdasarov, grâce à plusieurs de ses particularités, a permis d'obtenir plusieurs cristaux d'Yb:YAG avec profils de dopage variables contrôlés jusqu'à des valeurs de gradient de 3 at%/cm. Les résultats expérimentaux sont en bon accord avec les modèles mathématiques. Des simulations complémentaires de la température et du profil de gain montre que même avec des gradients plus faibles, les performances énergétiques des amplificateurs Lucia peuvent être améliorées jusqu'à 30%. Il est aussi alors possible d'utiliser des milieux à gain plus fins ce qui a pour conséquence positive une meilleure extraction de la chaleur. De larges cristaux d'Yb:YAG de 90 mm de diamètre ont été produits.
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Golub, Pavlo. "Chemical bonding analysis of complex solids in real space from the projector augmented-wave method." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-227653.
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Quantum mechanics became a foundation for incessant development of versatile computational methods for analysis of chemical and physical properties of molecules and crystals. A huge progress has been made in the fifield of density functional theory, since nowadays this theory offers the best compromise between precision of results and efficiency fiof computation. The chemical bonding analysis can be easily performed with real space methods based on chemical concepts introduced via partitioning of real space into chemically meaningful domains, since the orbital based approach is not well applicable due to the delocalized nature of plane waves. However the practical usage of those methods often requires a signifificant amount of computational resources. Some methods require the evaluation of so called domain overlap matrices, that is a formidable task for complex and low-symmetry systems. In the present research the author enables the investigation of complex solid compounds with real space chemical bonding indicators by introducing the derivation of the expression for the evaluation of the domain overlap matrix elements from the projected-augmented wave method. The corresponding program module was developed, which is capable to perform the real space chemical bonding analysis with a number of methods, like electron localizability indicators, electron localization function, localization/delocalization indices and domain averaged Fermi hole orbitals. The efficiency and the accuracy of the developed implementation is demonstrated by the comparison with the domain overlap matrix elements evaluation from the full-potential linearized augmented plane wave method on a set of simple compounds with three atoms per primitive cell at most. A set of complex periodic structures is analyzed and the capability of the present implementation to unravel intricate chemical bonding patterns is demonstrated.
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Ohaňka, Zdeněk. "Vliv velikosti částic a způsobu přípravy na hydrataci vápenato-hlinitých fází." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2018. http://www.nusl.cz/ntk/nusl-376802.
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This work focuses on the hydration of four calcium aluminate phases – C3A, C12A7, CA and CA2. Above all, the influence of particle size and method of preparation on hydration behaviour were studied. Influence of these factors on hydration products were also investigated. Calcium aluminates were prepared by solid state synthesis and amorphous citrate method. Both methods were described in detail. The particle size was determined by laser diffraction. Isothermic calorimetry was used to investigate the process of hydration. Hydration products were identified by X-ray diffraction analysis and simultaneous thermogravimetric and differential thermal analysis.
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Saalwächter, Kay. "Heteronuclear recoupling methods in solid state NMR." [S.l. : s.n.], 2000. http://ArchiMeD.uni-mainz.de/pub/2000/0070/diss.pdf.
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Freitas, Vânia Patrícia Castro Teixeira. "Organic-inorganic hybrids for green photonics." Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17325.
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Doutoramento em FísicaThe presente work aims to synthesize new bridge silsesquioxanes organic-inorganic hybrid materials, and characterize the local structure and photoluminescence properties overlooking potential applications in the area of green photonics, namely, in solid-state lighting and luminescent solar concentrators. In this context, three distinct families of materials based on six precursors which differ in their structural organization were synthesized, i.e. precursors with structure: 1) linear where the organic component is based on malonamide group, P2-m and P4-m; 2) linear which has been added an aromatic ring whose organic part is based on amide and/or thioamida, P(UU), P(UT) and P(TT) and 3) branched which the organic component is based on amide group, t-UPTES (5000). Two organic-inorganic hybrids (M2-m e M4-m) which results from hydrolysis and condensation of the precursors P2-m e P4-m were synthetized. The role of the presence of one or two malonamide groups was studied in terms of local structure and photoluminescence properties. Three organic-inorganic hybrids H(UU), H(UT) and H(TT) based on P(UU), P(UT) and P(TT) were synthesized and structurally characterized aiming to study the role of the hydrogen bond in the self-assembling of these materials. The presence of different types of hydrogen bonds (bifurcated, linear and cyclic) induces different conformations which affect the physical properties (mechanical and optical) of the materials. Hybrids based on t-UPTES(5000) precursor were synthesized based on different synthesis strategies. Changing the concentration of HCl and water content as well as the synthesis in a controlled environment allowed the improvement of the optical properties of this system, in particular, the absolute emission quantum yield and the absorption coefficient. In addition, it were studied the recombination mechanisms responsible for the emission through the comparison between the corresponding photoluminescence properties of the organic and inorganic models. Finally, due to the structural simplicity of the precursors P2-m and P4-m, these were doped with Eu3+. The local structure of the corresponding hybrids shows local coordination between the ion and the host. Efficient materials concerning the absolute emission quantum yield values motivated the development of luminescent solar concentrators with a maximum absolute emission quantum yield of 0.600.06 and optical conversion efficiency in the absorption spectral region (300-380 nm) of 12.3%.
O presente trabalho propõe sintetizar novos materiais híbridos orgânicos-inorgânicos do tipo silsesquioxanos em ponte e caracterizar a sua estrutura e propriedades de fotoluminescência com vista a potenciais aplicações na área da fotónica sustentável, nomeadamente, iluminação de estado sólido e concentradores solares luminescentes. Neste âmbito, foram sintetizadas três famílias distintas de materiais baseados em seis precursores que diferem na sua organização estrutural, ou seja, precursores com estrutura: 1) linear onde a componente orgânica é baseada no grupo malonamida, P2-m e P4-m; 2) linear onde foi adicionado um anel aromático cuja componente orgânica é baseada em amida e/ou thioamida, P(UU), P(UT) e P(TT), e 3) tri-ramificada onde a componente orgânica é baseada no grupo amida, t-UPTES(5000). Dois híbridos orgânicos-inorgânicos (M2-m e M4-m) que resultam da hidrólise e condensação dos precursores P2-m e P4-m foram sintetizados. O papel da presença de um ou dois grupos malonamida foi estudado em termos de estrutura local e propriedades de fotoluminescência. Três híbridos orgânicos-inorganicos, H(UU), H(UT) e H(TT), baseados, respetivamente, em P(UU), P(UT) e P(TT), foram sintetizados e caracterizados estruturalmente com o objetivo de estudar o papel das ligações de hidrogénio na auto-organização destes materiais. A presença de diferentes tipos de ligações de hidrogénio (bifurcada, linear e cíclica) induz diferentes tipos de configurações que têm influência nas propriedades físicas (mecânicas e óticas) dos materiais. Híbridos baseados no precursor t-UPTES(5000) foram sintetizados tendo em conta diferentes estratégias de síntese. A variação da concentração de HCl e quantidade de água bem como a síntese em ambiente controlado permitiram melhorar as propriedades óticas deste sistema nomeadamente, o rendimento quântico absoluto e o coeficiente de absorção. Foram também discutidos, os mecanismos de recombinação responsáveis pela emissão através da comparação das propriedades de fotoluminescência observadas nos correspondentes modelos orgânicos e inorgânicos. Finalmente, devido à simplicidade estrutural os precursores P2-m e P4-m, estes foram dopados com Eu3+. A estrutura local dos correspondentes híbridos mostra coordenação local entre o ião e a matriz. Materiais eficientes do ponto de vista de rendimento quântico absoluto motivaram o desenvolvimento de concentradores solares luminescentes que apresentam rendimento quântico absoluto máximo de 0.600.06 e eficiência ótica de conversão na região espetral de absorção (300-380 nm) de 12.3 %.
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Ball, Thomas James. "Development of new methods in solid-state NMR." Thesis, University of Glasgow, 2008. http://theses.gla.ac.uk/385/.
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Many chemically important nuclei are quadrupolar with half-integer spin (i.e., spin I = 1.5, 2.5, etc.) The presence of quadrupolar broadening for such nuclei can limit the information that may be extracted using NMR. MAS is able to remove first-order quadrupolar broadening but can only reduce the second-order contribution to the linewidth. The MQMAS and STMAS techniques have enabled high-resolution NMR spectra of half-integer quadrupolar nuclei in the solid state to be obtained by two-dimensional correlation under MAS conditions. Both of these experiments have several well-known limitations. One is that the conversion pulses in particular are very inefficient and the other is that the longer acquisition times required for two-dimensional experiments can be a limiting factor. Both of these disadvantages are addressed in this thesis. For the former case, existing composite pulse schemes designed to improve the efficiency of the conversion of multiple-quantum coherences are compared using 27Al and 87Rb MQMAS NMR of a series of crystalline and amorphous materials. In the latter case, a new experiment, named STARTMAS, is introduced that enables isotropic spectra of spin I = 1.5 spectra to be acquired in real time. The theoretical basis of the technique is explained and its applicability demonstrated using 23Na and 87Rb NMR of a wide range of solids. The nuclear Overhauser effect (NOE) is one of the most widely exploited phenomena in NMR and is now widely used for molecular structure determination in solution. NOEs in the solid state are rare and those to quadrupolar nuclei rarer still, this being due to the general absence of motion on the correct timescale and the usual efficiency of quadrupolar T1 relaxation, respectively. In this thesis, 11B{1H} transient NOE results are presented for a range of solid borane adducts. A comparison is made of the 11B NMR enhancements observed under MAS and static conditions and a rationale is proposed for the behaviour in the latter case.
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Haies, Ibraheem. "New methods for nitrogen-14 solid state NMR." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/382902/.
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Nitrogen is one of the most abundant elements. It plays a significant role in different scientific disciplines, like materials science, chemistry, biochemistry and pharmaceutical chemistry. Most NMR studies of nitrogen have been performed on samples enriched with 15N. To avoid enrichment and overcome the problem of using NMR where isotopic enrichment is not feasible, NMR of 14N that has 99.6% natural abundance is a viable alternative. However, the 14N spin quantum number 1 and high quadrupolar interactions lead to a few challenges for NMR investigation. Recently, two approaches appeared which overcome the complications associated to the first order quadrupolar line broadening, namely indirect detection using vicinal nuclei and overtone transition. Paper 1 describes a novel version of HMQC experiments, which requires the application of a moderate RF field to the 14N nucleus to correlate the 14N with a 13C ‘spy’ nucleus, which provides good sensitivity on natural abundance and labelled materials. In addition, overtone 14N NMR spectroscopy is a promising route for the direct detection of 14N signals with good spectral resolution. Overtone NMR is the main topic of my research. To overcome the poor efficiency of the overtone transition, polarization transfer techniques have been implemented. Papers 2 and 4 present respectively polarization transfer methods from 1H to the 14N overtone using symmetry-based R-sequences and cross polarization methods. Signal enhancements of 6.7 and 2 have been obtained when cross polarization methods and symmetry-based R-sequences are used respectively. Paper 3 shows results obtained with the DOR (double rotation) technique to reduce 14N overtone linewidth, with 14N overtone spectra with linewidth reduced by nearly one order of magnitude. Analysis of the results has been facilitated through the use of a new simulation strategy for 14N overtone NMR spectroscopy of spinning samples, using Spinach library.
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Asp, Grönhagen Klara. "Phase-field modeling of surface-energy driven processes." Doctoral thesis, KTH, Metallografi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11036.
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Surface energy plays a major role in many phenomena that are important in technological and industrial processes, for example in wetting, grain growth and sintering. In this thesis, such surface-energy driven processes are studied by means of the phase-field method. The phase-field method is often used to model mesoscale microstructural evolution in materials. It is a diffuse interface method, i.e., it considers the surface or phase boundary between two bulk phases to have a non-zero width with a gradual variation in physical properties such as energy density, composition and crystalline structure. Neck formation and coarsening are two important diffusion-controlled features in solid-state sintering and are studied using our multiphase phase-field method. Inclusion of Navier-Stokes equation with surface-tension forces and convective phase-field equations into the model, enables simulation of reactive wetting and liquid-phase sintering. Analysis of a spreading liquid on a surface is investigated and is shown to follow the dynamics of a known hydrodynamic theory. Analysis of important capillary phenomena with wetting and motion of two particles connected by a liquid bridge are studied in view of important parameters such as contact angles and volume ratios between the liquid and solid particles. The interaction between solute atoms and migrating grain boundaries affects the rate of recrystallization and grain growth. The phenomena is studied using a phase-field method with a concentration dependent double-well potential over the phase boundary. We will show that with a simple phase-field model it is possible to model the dynamics of grain-boundary segregation to a stationary boundary as well as solute drag on a moving boundary. Another important issue in phase-field modeling has been to develop an effective coupling of the phase-field and CALPHAD methods. Such coulping makes use of CALPHAD's thermodynamic information with Gibbs energy function in the phase-field method. With the appropriate thermodynamic and kinetic information from CALPHAD databases, the phase-field method can predict mictrostructural evolution in multicomponent multiphase alloys. A phase-field model coupled with a TQ-interface available from Thermo-Calc is developed to study spinodal decomposition in FeCr, FeCrNi and TiC-ZrC alloys.QC 20100622
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Senanayake, Nishan M. "Exploring Heusler Alloys as Catalysts for Ammonia Dissociation." Bowling Green State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1467314800.
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Ibbett, D. A. "A developmental system for solid state NMR imaging." Thesis, University of Kent, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380989.
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Boland, Martin Peter. "Evaluation of solid-state NMR methods for drug discovery." Thesis, University of Manchester, 2005. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549037.
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Ralph, Adam Charles. "Physical and direct methods in crystallography." Thesis, University of York, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304487.
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Avadhut, Yamini. "Quantitative solid state nuclear magnetic resonance methods for inorganic materials." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-153598.
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Péraud, Jean-Philippe M. (Jean-Philippe Michel). "Efficient multiscale methods for micro/nanoscale solid state heat transfer." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101537.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 193-199).
In this thesis, we develop methods for solving the linearized Boltzmann transport equation (BTE) in the relaxation-time approximation for describing small-scale solidstate heat transfer. We first discuss a Monte Carlo (MC) solution method that builds upon the deviational energy-based Monte Carlo method presented in [J.-P. Péraud and N.G. Hadjiconstantinou, Physical Review B, 84(20), p. 205331, 2011]. By linearizing the deviational Boltzmann equation we formulate a kinetic-type algorithm in which each computational particle is treated independently; this feature is shown to be consequence of the energy-based formulation and the linearity of the governing equation and results in an "event-driven" algorithm that requires no time discretization. In addition to a much simpler and more accurate algorithm (no time discretization error), this formulation leads to considerable speedup and memory savings, as well as the ability to efficiently treat materials with wide ranges of phonon relaxation times, such as silicon. A second, complementary, simulation method developed in this thesis is based on the adjoint formulation of the linearized BTE, also derived here. The adjoint formulation describes the dynamics of phonons travelling backward in time, that is, being emitted from the "detectors" and detected by the "sources" of the original problem. By switching the detector with the source in cases where the former is small, that is when high accuracy is needed in small regions of phase-space, the adjoint formulation provides significant computational savings and in some cases makes previously intractable problems possible. We also develop an asymptotic theory for solving the BTE at small Knudsen numbers, namely at scales where Monte Carlo methods or other existing computational methods become inefficient. The asymptotic approach, which is based on a Hilbert expansion of the distribution function, shows that the macroscopic equation governing heat transport for non-zero but small Knudsen numbers is the heat equation, albeit supplemented with jump-type boundary conditions. Specifically, we show that the traditional no-jump boundary condition is only applicable in the macroscopic limit where the Knudsen number approaches zero. Kinetic effects, always present at the boundaries, become increasingly important as the Knudsen number increases, and manifest themselves in the form of temperature jumps that enter as boundary conditions to the heat equation, as well as local corrections in the form of kinetic boundary layers that need to be superposed to the heat equation solution. We present techniques for efficiently calculating the associated jump coefficients and boundary layers for different material models when analytical results are not available. All results are validated using deviational Monte Carlo methods primarily developed in this thesis. We finally demonstrate that the asymptotic solution method developed here can be used for calculating the Kapitza conductance (and temperature jump) associated with the interface between materials.
by Jean-Philippe Péraud.
Ph. D.
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Cai, Yu-Sin, and 蔡育欣. "Preparation of ZnS phosphor by solid-state sintering method." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/2e72uq.
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碩士國立東華大學
材料科學與工程學系
100
In this study, zinc sulfide (ZnS) phosphors powders are prepared by solid-state sintering method. The effects of sintering temperature, dopant, and selection of flux on the luminescence properties are investigated. X-ray diffraction (XRD), photoluminescence spectrometer (PL), field-emission scanning electron microscopy (FE-SEM), and energy dispersive x-ray spectroscopy (EDS) are used to investigate the crystal structure, luminescence properties, and powder structures identified. ZnS is Ⅱ-Ⅵ group semiconductor material, generally used in phosphors powder, also applied in electroluminescence devices and light-emitting diode. ZnS have good luminous properties and is a candidate material for phosphors that emit visible light. The ZnS thin is sintered under the temperature of 600 ℃~900 ℃ in the nitrogen atmosphere and blue-green light (523 nm) is achieved for the films. Orange-yellow light (585 nm) is achieved for ZnS films doped with manganese.Experimental results reveal both manganese dopant and fluxing NaCl can enhance the luminous intensity of the ZnS powder.
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TU, CHIH-CHENG, and 塗智丞. "Preparation of Zn2SiO4:Mn Phosphors by Solid State Method." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/egh4y7.
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碩士國立高雄科技大學
微電子工程系
107
In this study, the preparation of inorganic phosphor powder was carried out by solid-state method using zinc oxide (ZnO) and silicon dioxide (SiO2) as raw materials. The raw materials of ZnO : SiO2 ((2~1):1) were mixed with the activator MnO2 and then they were sintered. The properties of the samples were analyzed by XRD, PL and SEM. The effect of activator content on fluorescence characteristics was investigated. XRD analysis showed that the sintering temperature must be at least 1100 °C to obtain zinc silicate ( α- Zn2SiO4 )structure. At the same time, residual zinc oxide is also found in the synthesized materials. To improve the problem of zinc oxide residue, the mixed rate of ZnO to SiO2 was reduced from 2:1 to 1:1. The obtained Zn2SiO4:Mn2+phosphor shows green light fluorescent luminescence(FL) at the wavelength of about 526 nm under 280 nm UV excitation. The sample doped with 0.2 mol Mn2+ shows the strongest FL. The Mn2+ FL emission corresponds to the transition of the electrons from the 4T1 excited-state to the 6A1 ground-state. Furthermore, the raw material ratio of ZnO to SiO2 is found to have great influence on FL emission. As the ratio of ZnO to SiO2 is reduced to 1:1, the sample has the best FL emission.
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Tsai, C.-H., and 蔡正雄. "Photoluminescence of Sr2MgSi2O7¬:Eu3+ Phosphor Prepared by Solid State Reaction Method." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/nc59q7.
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碩士國立臺北科技大學
材料科學與工程研究所
99
The study used the solid state reaction to prepare the Sr2MgSi2O7:Eu3+ Phosphor .We found the optimal parameters to synthesize the Host, Sr2MgSi2O7 ,by different calcined temperature、holding time、different H3BO3 c Concentration .We probe the influence of luminescence characteristic on Sr2MgSi2O7：Eu3+ phosphors by different doping concentration of Eu The result shows the sharp emission peak at 613nm that attributed to the typical f→f transition of Eu3+, whereas the emission peaks﹕578nm、589nm、613nm、652nm、702nm are attributed to the Eu3+ 5D0→7FJ=0 to 4 at the excitation 395nm. The luminous intensity increased as raising the concentration of activator, and the maximum luminous intensity was observed with Eu 6mole%、H3BO3 5wt% ,and fired at 1350°C for 4hours.
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HUNG, CHIEN-YU, and 洪阡郁. "Development of a new solid state culture method for Antrodia cinnamomea." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/9tq25u.
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碩士銘傳大學
生物科技學系碩士班
107
Many experiments are studying changing medium components and culture methods to promote the growth of mycelium of Antrodia cinnamomea and enhance the efficacy of mycelium. In this study, the effects of addition of Cinnamomum kanehirae Hayata wood meal, soybean flour and farina tritici on the growth and metabolite production were tested in the experiment. In addition, dsign incubators with different angles to cultivate Antrodia cinnamomea and observe the growth of mycelium and mtabolite production. In the above experiment, it can observed that the addition of a few amount of wood meal and farina tritici can promote the growth of mycelium. And the addition of a few amount of wood meal, soybean flour and farina tritici could enhance the antioxidation ability. Adenosine content is not enhance by the additives. In the experiment of self-made incubator, it was found that when the angel was 60∘, the growth diameter of mycelium is largest and increase adenosine content. However, the effect of different angles of placement on the improvement of antioxidation ability varies depending on the species.
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Lee, You-Wei, and 李祐瑋. "Preparation of Lithium Aluminosilicate Nanopaticles by Solid-State Method and Purification." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/10915919587874373200.
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碩士明志科技大學
化學工程系碩士班
102
Abstract This researches are primarily exploring preparation of Lithium Aluminosilicate nanoparticles and purification through the Size Exclusion Chromatography of HPLC (HPLC-SEC). The study is constitutes with two main parts. (1) Generally accessible SiO2 will be used to examine whether or not the application of HPLC-SEC by inorganic nanoparticles grading. While exploring appropriateness of detectors, the result of the experiment demonstrates that intensity of UV detector will vary directly proportional to SiO2, which reveals that there is a relationship between SiO2 and HPLC of detectors; extract in red polarity effect, the methanol content of 0% would be the best condition; from the HPLC-SEC application to SiO2 particle size classification, the fact that inorganic nanoparticles can be used to perform HPLC-SEC is proved. (2) Using the solid state reaction method to preparation LAS powder will result in problems such as agglomeration and particle coarsening. To cope with the phenomenon, particle coarsening, the use of nano-bead mill may be required to make appropriate reduction in the diameter of particle. In terms of the impurities, pollution, HPLC-SEC should be the solution to it. The outcome of the experiment shows that speed of 2500 rpm and a bead mill bead mill time 4h are the best conditions. The addition of CTAB dispersant LAS can better stabilize nano particles; using 0.3mm zirconia ball, bead mill reduce the diameter to approximately 70nm can meet the appropriate size of condition to perform HPLC-SEC Finally, The bead mill was contaminated LAS powder were isolated and purified through HPLC-SEC HPLC-SEC analysis appears in Figure elution peak elution time 8.2min and 14.3min, with a resolution of 2.03. To EDS composition analysis, proving HPLC-SEC can LAS roughly separation and purification of nanoparticles.