Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 21 for “"first-Principles methods"”.
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The electronic and mechanical properties of the XYB14 complex borides studied by first-principles methods
… is related to its chemical composition. Based on first-principles methods, a series of calculations are performed to examine the relationship between the chemical bonding and the mechanical properties of XYB14. The impact of substituting different atomic species into both metal and boron sites is …
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Ferroelectricity Coupled To Octahedral Rotations In Perovskite Oxides From First Principles
… appear together and are strongly coupled. We use first-principles methods and simple physical models to elucidate trends across multiple materials. The first part of this thesis introduces a new model for the interplay of ferroelectricity and octahedral rotations based on ferri-electricity. The …
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Models for transition metal oxides and for protein design
… materials can now be predicted with standard first-principles methods such as the Local Density (LDA) or Generalized Gradient Approximation (GGA). However, known problems exist when using these methods for predicting the electronic structure and total energy of transition metal oxides. We …
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A first principles study of defects in titanium: interaction of twin boundaries with dislocations and oxygen interstitials
… through computer simulations. While recent first-principles methods predict dislocation core structures and boundary geometries and energies, modeling a dislocation near a boundary requires new techniques to treat the long range strain field of the dislocation near a boundary. Using flexible …
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Computational modeling of defects in nanoscale device materials
… electronic devices has been a long-term goal of first-principles methods. First principles simulations are performed in this thesis, consisting of density functional theory (DFT) supplemented with many body perturbation theory (MBPT) methods, of native defects in bulk and slab models of …
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First-principles and Many-Body Methods: Implementations and Applications to Study Spintronic Materials
… and a magnetoresistive material Ta2PdSe6 with first-principle and many-body methods. Particularly, we investigate the Mn valence in (Ga,Mn)N and derive low-energy models of (Ga,Mn)N by making use of a first-principles Wannier-function analysis. Additionally, we also study the disorder-driven …
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Ab initio computational applications to complex biomolecular systems
… molecules ― have been studied using ab initio (first-principles) methods. By investigating the properties of water as the preliminary step, the hydrogen bond (HB) interactions, which play important roles in biomolecules, were better understood from the quantum mechanical viewpoint. The …
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Degradation of Cd-yellow pigment: an ab initio study of defects and adsorption of oxygen and water on CdS
… energies are determined with the use of a first principles method. All the calculations are performed within the framework of the Density Functional Theory (DFT) in the Generalized Gradient Approximation (GGA-PBE) with the use of ultrasoft pseudopotentials. Despite the standard DFT-GGA …
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Extending first principles spectroscopy to disordered materials: a study on amorphous and crystalline aluminas
… to experiment, it is then necessary to extend first principles calculations of NMR and XAS to amorphous materials. In this thesis, I apply first principles methods for calculating NMR and XAS spectra, to both crystalline and amorphous phases of alumina (Al₂O₃). First, I analyze the Al K-edge …
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Novel methods to predict solid-state material properties
… attempted in practice. Accurate and inexpensive methods to tackle the atomic-scale problem are a prerequisite for materials discovery. We begin with a description of existing methods. This is followed by the development of a Monte Carlo method to calculate expectation values from the many-body …
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A first principles investigation of transitional metal doping in lithium battery cathode materials
… of mixed-metal intercalation oxides. Using first-principles methods, the effect of doping on the mixing, energetic, and voltage properties as well as the phase diagrams of lithium transition-metal oxides for lithium battery cathode materials was investigated. The effect of doping on the …
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Multiscale Simulations of Dynamics of Ferroelectric Domains
… of computational power and the success of first-principles methods, large-scale simulations of dynamics in oxides at finite temperature can still only be performed using classical atomistic potential. We first develop a model potential based on principles of bond-valence and bond-valence …
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First-Principles Studies of Complex Oxide Materials
This thesis uses first-principles methods to study complex oxide materials. The first part of the thesis deals with complex oxide materials that have applications as lithium-ion battery electrodes. In the second part, a new method for the calculation of vibrational properties of correlated …
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Atomic structures and properties of oxide interfaces
This thesis uses computational approaches, mainly first-principles methods, to study interfaces in oxide thin films. One of the difficulties in interface studies is the lack of definitive atomistic models, yet they are essential input for any calculations. Here, this problem is tackled by ab initio …
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Magnetostructural phase transformations in magnetic shape memory Heusler alloy Ni-Mn-In
Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2025-03-28 without embargo terms
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Interplay of Transition Metals and Noncovalent Interactions in C–H Activation Catalysis
… Studying the mechanism of metalloenzymes using first principles methods could be challenging due to the larger system sizes. Thus, we also try to understand C–H activation carried out by 3d TMCs focusing on the specific case of partial oxidation of methane to methanol. While the oxidation and …
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First-principles investigation of transport and magnetism
… novel properties. Density functional based first-principles methods provide us with the necessary tools to approximate the Schrödinger's equation for many-electron periodic solids. Starting from the atomic position of their constituent atoms, using one of the most accurate methods of …
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Unique cluster expansion for reliable first-principles prediction of alloy thermodynamics and phase diagrams
… applications. Using structural energies from first-principles electronic theory, an effective (CE) Hamiltonian that is suitable for large scale systems is constructed, enabling the calculation of thermodynamic quantities and prediction of phase diagrams. The CE Hamiltonian is expanded in terms …
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First-principles investigations of transition metal hyperdoped silicon and germanium for intermediate band engineering
… which are as follows. (i) Carrying out first-principles investigations of gold hyperdoped silicon to provide detailed insights into recent extensive experimental investigations. This analysis helps to reveal the origins of the sub band gap optical response observed in this system, as …
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Theory of magnetic transition metal nanoclusters on surfaces
… been accelerated by the many novel experimental methods and techniques developed exhibiting atomic resolution. This thesis is motivated by the quest for the understanding and the exploration of complex magnetism provided by atomic scale magnetic clusters deposited on surfaces or embedded in the …
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