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 108 for “"First-principles calculations"”.
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First principles calculations on ZnO non-equilibrium phase
… the BN phase and the equilibrium WZ phase, first principles approaches such as DFT, hybrid functional and the GW approximation have been studied and applied. The lattice constant has been obtained by performing full relaxation within the DFT approximation. With the DFT optimized structure, …
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First principles calculations of transition metal complexes for artificial photosynthesis
… has been developed using a combination of first principles techniques and analysis code. In the development of the workflow, this study focused on a vanadium(V) oxo compound VOLF which has been experimentally synthesized by collaborators. To fully understand the properties of this light …
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Examining Topological Insulators and Topological Semimetals Using First Principles Calculations
The importance and promise that topological materials hold has been recently underscored by the award of the Nobel Prize in Physics in 2016 ``for theoretical discoveries of topological phase transitions and topological phases of matter." This dissertation explores the novel qualities and useful …
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AN INVESTIGATION OF LITHIUM SOLID ELECTROLYTE MATERIALS WITH FIRST PRINCIPLES CALCULATIONS
Inorganic solid electrolyte materials have recently become the focus of considerable
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Optical and electronic properties of defective semiconductors from first principles calculations
… In this dissertation, we apply state-of-the-art first-principles approaches based on density functional theory (DFT) and many-body perturbation theory (MBPT) to quantitatively describe trap state energies and optical excitation spectra of defective bulk gallium nitride (GaN) and monolayer …
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Hyperelastic continuum modeling of cubic crystals based on first-principles calculations
… of the equilibrium crystal phase. For the first time, we combine the formalism of continuum mechanics invariant theory with the predictive capability of quantum mechanics to model the hyperelastic response of cubic crystals. We use a complete and irreducible basis of strain invariants to …
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Thermodynamics of metal hydrides for hydrogen storage applications using first principles calculations
… for improving metal hydride thermodynamics. First, our calculations for examining the relation between the particle size of simple metal hydrides and thermodynamics of their decomposition reactions provide that the relation would depend on the total surface energy difference between a metal …
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Dielectric response and interactions in low-dimensional carbon materials from first principles calculations
Includes bibliographical references (p. 155-162).
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Combining Experiments and First-Principles Calculations to Understand and Engineer Metal Exsolution in Perovskites
… through a combination of experimental work and first-principles atomistic modelling with the long-term goal of accelerating the commercialization of exsolution materials. We first investigate the impact of perovskite composition on the properties of Ni nanoparticles exsolved from bulk …
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Hydrogen migration in monoclinic ZrO₂ and the effects of defects and dopants assessed by first-principles calculations
… oxide layer contacting the cooling water. First principles calculations are casted to study hydrogen migration at atom-istic scale. All possible stable sites for hydrogen to take in the structure are determined based on energy minimization. Barriers and saddle point configurations of …
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Insights into formation of semiconductor nanocrystals : from first principles calculations to kinetic models of nucleation and growth
… aims to address this challenge by utilizing first principles calculations and mathematical modeling to study the formation of cadmium selenide nanocrystals, the most frequently studied and best characterized nanocrystal system. In the first part of this thesis we investigate the elementary …
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Electronic structure and quantum conductance of nanostructures
… and application of a novel large-scale first-principles approach to study the electronic structure and quantum conductance of realistic nanoscale materials. Electron transport at the nanometer scale involves phenomena which are beyond the realm of classical transport theory: the wave …
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Magnetic ordering in systems of reduced dimensionality
… These models were conditioned on a mapping from first principles calculations to the Ising model. The effect of the suggested octopolar reconstruction for the polar (111) surfaces of FCC was also examined.
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Nanopartículas magnéticas adsorvidas em superfícies metálicas
… this kind of system is studied theoretically by first principles calculations, based on the density functional theory (DFT), as well as by tight binding models. We study different Fe-based structures adsorbed on the Cu(001) surface. The systems studied here include Fe adatoms, dimers and wires …
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Transport of phonons and electrons in thermoelectric materials and graphene
… thermoelectric materials and graphene using both first principles calculations and experimental characterizations. We start by studying phonon transport in Bi and Bi-Sb alloys using first principles calculations. A notable observation from this calculation is that a strong long-range interaction …
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STM Study of Interfaces and Defects in 2D Materials
… 2D transition metal dichalcogenides (TMDCs). The first part of the thesis focuses on the synthesis of 2D TiSe2 with chemical vapor transport (CVT). By properly choosing the growth condition, Sub-10 nm TiSe2 flakes were successfully obtained. A 2 × 2 charge density wave (CDW) was clearly observed …
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Lead-related quantum emitters in diamond
… and high temperature vacuum annealing. First-principles calculations predict a negatively-charged Pb-vacancy center in a split-vacancy configuration, with a zero-phonon transition around 2.3 eV. Cryogenic photoluminescence measurements performed on emitters in nanofabricated pillars …
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Effect of interface structure on film polarization and surface chemistry in ultra-thin TiO2/BaTiO3 Heterostructures
… of the material system. In this work, using first-principles total-energy electronic structure methods based on density functional theory, we investigate how the photocatalytic activity of anatase titanium dioxide ultra-thin films can be tuned via heteroepitaxial integration with a …
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Angle-resolved photoemission studies of thin-film topological materials
… photoemission spectroscopy (ARPES) and first-principles calculations. We have studied the electronic structure of Bi2Te3 films using ARPES with circularly-polarized lights. Our ARPES results show a thickness-dependent electronic structure of Bi2Te3 films. In addition, we have studied the …
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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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