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The Mixed Glass Former Effect- Modeling of the Structure and Ionic Hopping TransportSchuch, Michael 11 October 2013 (has links)
The origin of the Mixed Glass Former Effect (MGFE) is studied, which manifests itself in a non-monotonic behavior of the activation energy for long-range ion transport as a function of the mixing ratio of two glass formers. Two theoretical models are developed, the mixed barrier model and the network unit trap model, which consider different possible mechanisms for the occurrence of the MGFE. The mixed barrier
model is based on the assumption that energy barriers are reduced for ionic jumps in regions of mixed composition. By employing percolation theory it is shown that this mechanism can successfully account for the behavior of the activation energy in various ion conducting mixed glass former glasses. The network unit trap model is based on the fact that a variety of network forming units, the so-called Q(n) species, can be associated with one glass former. Using a thermodynamic approach, the change of the concentration of these units in dependence of ionic concentration and the glass former mixing ratio is successfully predicted for alkali borate, phosphate and borophosphate glasses. In a second step, the charge distribution of the various units is considered and related to it, the binding energies to alkali ions. This gives rise to a modeling of the ionic transport in an energy landscape that changes in a defined manner with the glass former mixing ratio. Kinetic Monte Carlo simulations for alkali borophosphate glasses, which serve as a representative system for the MGFE in the literature, demonstrate that this approach succeeds to predict the behavior of the activation energy.
In a further part of the thesis, Reverse Monte Carlo (RMC) simulations for the atomic structure of sodium borophosphate glasses are carried out with X-ray and neutron diffraction data as further input from
experiments. Three-dimensional structures could be successfully generated that are in agreement with all experimental and theoretical constraints. Volume fractions of the ionic conduction pathways determined from these structures, however, do not show a substantial relationship to the activation energy, as earlier proposed in the iterature for alkali borate and alkali phosphate glasses.
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General Projective Approach to Transport Coefficients of Condensed Matter Systems and Application to an Atomic WireBartsch, Christian 16 March 2010 (has links)
We present a novel approach to the investigation of transport coefficients in condensed matter systems, which is based on a pertinent time-convolutionless (TCL) projection operator technique. In this context we analyze in advance the convergence of the corresponding perturbation expansion and the influence of the occurring inhomogeneity.
The TCL method is used to establish a formalism for a consistent derivation of a Boltzmann equation from the underlying quantum dynamics, which is meant to apply to non-ideal quantum gases. We obtain a linear(ized) collision term that results as a finite non-singular rate matrix and is thus adequate for further considerations, e.g., the calculation of transport coefficients. In the work at hand we apply the provided scheme to numerically compute the diffusion coefficient of an atomic wire and especially analyze its dependence on certain model properties, in particular on the width of the wire.
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Line defects in conformal field theory / From weak to strong couplingBarrat, Julien 14 March 2024 (has links)
Die konforme Feldtheorie findet in verschiedenen Bereichen Anwendungen, von statistischen Systemen in der Nähe kritischer Punkte bis hin zur Quantengravitation durch die AdS/CFT-Korrespondenz. Diese Theorien unterliegen starken Einschränkungen, die eine systematische nicht-perturbative Analyse ermöglichen. Konforme Defekte bieten eine kontrollierte Möglichkeit, die Symmetrie zu brechen und neue physikalische Phänomene einzuführen,
während wichtige Vorteile der zugrunde liegenden konformen Symmetrie erhalten bleiben. Diese Dissertation untersucht konforme Liniendefekte sowohl im schwachen als auch im starken Kopplungsregimes. Es werden zwei verschiedene Klassen von Modellen untersucht. Wir konzentrieren uns zuerst auf die supersymmetrische Wilson-Linie in N = 4 Super Yang-Mills, die als ideales Testfeld für die Entwicklung innovativer Techniken wie dem analytischen
konformen Bootstrap dient. Die zweite Klasse besteht aus magnetische Linien in Yukawa-Modellen, die faszinierende Anwendungen in 3d kondensierten Materiesystemen haben. Diese Systeme haben das Potenzial, Phänomene des Standardmodells in einem Niedrigenergieszenario nachzubilden. / Conformal field theory finds applications across diverse fields, from statistical systems at criticality to quantum gravity through the AdS/CFT correspondence. These theories are subject to strong constraints, enabling a systematic non-perturbative analysis. Conformal defects provide a controlled means of breaking the symmetry, introducing new physical phenomena while preserving crucial benefits of the underlying conformal symmetry. This thesis investigates conformal line defects in both the weak- and strong-coupling
regimes. Two distinct classes of models are studied. First, we focus on the supersymmetric Wilson line in N = 4 Super Yang–Mills, which serves as an ideal testing ground for the development of innovative techniques such as the analytic conformal bootstrap. The second class consists of magnetic lines in Yukawa models, which have fascinating applications in 3d condensed-matter systems. These systems have the potential to emulate phenomena observed in the Standard Model in a low-energy setting.
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Strukturelle Untersuchung der amorph/kristallinen Grenzfläche mittels quantitativer hochauflösender Transmissionselektronenmikroskopie an den Systemen a-Si/c-Si und a-Ge/c-Si / Structural investigation of the amorphous/crystalline interface by means of quantitative high-resolution transmission electron microscopy on the systems a-Si/c-Si and a-Ge/c-SiThiel, Karsten 02 November 2006 (has links)
No description available.
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Elektronische Eigenschaften neuer dotierter Halbleiter / Supraleitung im Diamant und Transporteigenschaften von RuIn<sub>3</sub> / Electronic properties of newly-discovered doped semiconductors / Superconductivity in diamond and transport properties of RuIn<sub>3</sub>Bogdanov, Dmitrij 01 August 2006 (has links)
No description available.
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Investigation of the segregation behaviour in nanocrystalline materialsWille, Catharina Gabriele 30 October 2009 (has links)
No description available.
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Symmetriebrechende Gitterverzerrung in einer elektronischen nematischen Phase / Symmetry-Breaking Lattice Distortion in an Electronic Nematic PhaseStingl, Christian 31 May 2011 (has links)
No description available.
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Oxidation und epitaktische Oxidation von Nickel und Nickellegierung / Oxidation and epitaxial oxidation of Nickel and Nickel alloysBrandt, Cirsten Maja 16 August 2002 (has links)
No description available.
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Current-Induced Excitations in Ferromagnetic Single Layer and Trilayer Nanodevices / Spinstrominduzierte Anregungen in nanostrukturierten ferromagnetischen Einfach- und DreifachlagenParge, Anne 23 March 2007 (has links)
No description available.
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InN and In-rich InGaN Nanocolumns by Molecular Beam Epitaxy / InN und In-reiche InGaN Nanodrähte mittels MolekularstrahlepitaxyDenker, Christian 08 November 2011 (has links)
No description available.
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