Дисертації з теми "Periodic density functional theory"
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Todorova, Tanya Kumanova. "Periodic density functional study on supported vanadium oxides." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2007. http://dx.doi.org/10.18452/15680.
Повний текст джерелаSupported vanadium oxide catalysts are of high interest because of their potential in a wide variety of oxidation reactions. A key step to fully understand the catalytic mechanism is a profound knowledge of the microscopic structure of the active vanadia species under various conditions and the way they are anchored to the support material. In the present work, density functional theory in combination with statistical thermodynamics is employed to investigate two vanadia-based systems, i.e., vanadia/alumina and vanadia/silica. The alumina support is modeled using the stable alpha-Al2O3 and the metastable kappa-Al2O3 phases, whereas ultrathin SiO2 film epitaxially grown on Mo(112) is employed as a silica support. The unique atomic structure of the latter as well as that of the one-dimensional silica stripes, found to coexist with the film in a perfect registry, are precisely determined based on combined theoretical and experimental studies. Moreover, the formation of a new, "O-rich" phase of the SiO2/Mo(112) film is predicted, whose existence is subsequently experimentally confirmed. The aim of the thesis is to provide an understanding on how vanadia aggregates anchor to the surface and to examine the role of the oxide support on the molecular and electronic structure of the stable VOx species. The efforts have focused on finding correlations between structural properties and catalytic activity in reactions proceeding via the Mars-van Krevelen mechanism. In accord therewith, the formation energy of a lattice oxygen defect is used as an indicator of catalytic performance. The influence of the support structure on the interface vibrational modes is analyzed in an attempt to shed light on the origin of the characteristic bands observed in the experimental spectra of vanadia/alumina and vanadia/silica model catalysts.
Lourenço, Mirtha Alejandra de Oliveira. "Tuning functionalized periodic mesoporous organosilicas for CO2/CH." Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/21817.
Повний текст джерелаEsta tese de doutoramento teve como principal objetivo a conceção de novas organossílicas mesoporosas periódicas (PMOs) para aplicação na separação de misturas gasosas de dióxido de carbono e metano. Materiais PMOs, com grupos fenileno e bifenileno bissililados, foram modificados por introdução de grupos funcionais amina, utilizando uma das seguintes metodologias: i) reação de co-condensação; ii) pós-modificação da ponte orgânica; iii) "grafting". O tamanho dos poros das PMOs funcionalizadas e não funcionalizadas foi definido pelo tamanho da cadeia alquilada da molécula molde (surfactante) utilizada na síntese do material poroso. Estudou-se o efeito do diâmetro dos poros na separação de CO2/CH4. Investigou-se também estratégias alternativas para modificar as propriedades físico-químicas dos materiais através de reações de superfície utilizando irradiação de micro-ondas; deposição de camada atómica (ALD) de óxido de alumínio; e carbonização dos materiais em atmosfera inerte. A investigação experimental foi efectuada em paralelo com estudos computacionais. Realizou-se um estudo de simulação molecular recorrendo ao método de DFT, e usando um arranjo regular de grupos fenileno-sílica, para determinar as características ideais dos materiais para promover a separação de metano do dióxido de carbono em misturas destes gases. Foi utilizado um modelo simples, obtido pela repetição de uma célula unitária com 3 anéis fenileno, para simular a parede dos materiais PMOs e desta forma selecionar e avaliar as interações entre os gases e os grupos funcionais presentes na superfície dos materiais. A tendência do rácio entre energias de interação entre a estrutura da parede do fenileno - PMO e as moléculas de CO2 e de CH4 foi concordante com os rácios das constantes de Henry obtidos pela técnica de adsorção. Demonstrou-se uma boa sinergia entre tarefas experimentais e computacionais, o que permite a otimização de recursos, evitando a síntese desnecessária de materiais que se antecipem serem pouco eficazes para o processo de separação de misturas gasosas CO2 e CH4. Assim, a abordagem seguida nesta tese para alcançar adsorventes eficazes foi baseada numa conjugação interdisciplinar envolvendo troca de informação entre as tarefas de síntese, modelação computacional e adsorção.
The main objective of this PhD Thesis was the design of periodic mesoporous organosilicas (PMOs) for applications in carbon dioxide and methane separation. Novel PMOs were prepared by the modification of phenylene and biphenylene PMO materials with different amine functionalities through one of the three following synthetic strategies: i) co-condensation reaction; ii) organic bridge post-modification; or/and iii) grafting. The pore size of both functionalized and non-functionalized phenylene PMOs was regulated by the size of the alkyl-chain in the surfactant template. Materials with different pore sizes were used to understand the influence of the pore diameter on the CO2/CH4 separation. Additionally, it was aimed to explore alternative strategies to modify the physical-chemical properties of the materials such as microwave-assisted functionalization; atomic layer deposition (ALD) of aluminum oxide at the PMO surfaces; and carbonization of the PMO materials. The experimental research was performed in parallel with computational studies. A molecular simulation study, using the DFT method and a regular arrangement of phenylene-silica groups, of the ideal characteristics of the adsorbent materials, for CO2/CH4 separation was performed. It was used a simple model of the wall of the PMO materials obtained by the repetition of a unit cell with 3 phenylene rings, to select and evaluate interactions between gases and functional groups in the surface of the materials. The tendency between the ratio of the interaction energies between the wall structure of the phenylene-PMO and the CO2 and CH4 molecules was in good agreement with the ratio of the Henry constants achieved by the adsorption technique. Therefore, a good synergy between experimental and computational tasks was implemented to optimize the resources, avoiding the synthesis of ineffective materials. Thus, the strategy of this PhD Thesis to achieve effective adsorbents was based on an interdisciplinary approach and on the ability to link and interchange information between synthetic, computer modeling and adsorption experiments
Laino, Teodoro. "Multigrid QM/MM approaches in ab initio molecular dynamics." Doctoral thesis, Scuola Normale Superiore, 2006. http://hdl.handle.net/11384/85799.
Повний текст джерелаBurow, Asbjörn Manfred. "Methoden zur Beschreibung von chemischen Strukturen beliebiger Dimensionalität mit der Dichtefunktionaltheorie unter periodischen Randbedingungen." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16415.
Повний текст джерелаThis work contributes to the field of theoretical chemistry and is aimed at the development of efficient methods for computation of the electron density and the energy belonging to the ground state of molecular and periodic systems. It is based on the use of Kohn Sham density functional theory (Kohn Sham DFT) and local basis functions. In this scope, the molecular and the periodic systems of any dimensionality (e.g., bulk crystals, thin films, and polymers) are treated on an equal footing using methods which are easy to implement, numerically accurate, and highly efficient. For this, the author has augmented established methods of molecular simulations for their use with periodic boundary conditions applying novel techniques. These methods have been combined to a complete DFT method. Among these methods, the innovative approach for the RI (resolution of identity) method applied to the Coulomb term represents the key technology of this work. As a striking feature, this approach operates exclusively in real space. Although the RI method is the chief ingredient, the development of further methods is required to achieve overall efficiency for the consumption of storage and time. One of these methods is used to compress the density and Kohn Sham matrices. Moreover, numerical integration of the exchange-correlation term has been improved applying an adaptive numerical integration scheme. The methods presented in this thesis are combined to the prototype of an RI-DFT program. Using this program single point energies on the gamma point can be calculated for systems with closed shells. Calculations have been performed and the results are used to assess the accuracy and efficiency achieved. This program forms the foundation of an efficient and competitive DFT code. It works numerically accurate and treats molecules and periodic systems on an equal footing.
Schweigert, Igor Vitalyevich. "Ab initio Density Functional Theory." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011614.
Повний текст джерелаLaming, Gregory John. "Density functional theory for molecules." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336907.
Повний текст джерелаChan, G. K. L. "Aspects of density functional theory." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597413.
Повний текст джерелаEsplugas, Ricardo Oliveira. "Density functional theory and time-dependent density functional theory studies of copper and silver cation complexes." Thesis, University of Sussex, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496931.
Повний текст джерелаTaga, Adrian. "Materials Engineering Using Density Functional Theory." Doctoral thesis, KTH, Materials Science and Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3809.
Повний текст джерелаThis doctoral thesis presents density functionalcalculations applied in several domains of interest in solidstate physics and materials science. Non-collinear magnetismhas been studied both in an artificial multi-layer structure,which could have technological relevance as a magnetic sensordevice, and as excitations in 3d ferromagnets. The intricatebulk crystal structure of γ-alumina has been investigated.An improved embedded cluster method is developed and applied tostudy the geometric and electronic structures and opticalabsorption energies of neutral and positively charged oxygenvacancies in α-quartz. Ab initio total energycalculations, based on the EMTO theory, have been used todetermine the elastic properties of Al1-xLixrandom alloys in the face-centered cubiccrystallographic phase. The obtained overall good agreementwith experiment demonstrates the applicability of the quantummechanics formulated within the framework of the DensityFunctional Theory for mapping the structural and mechanicalproperties of random alloys against chemical composition.
Kaduk, Benjamin James. "Constrained Density-Functional Theory--Configuration Interaction." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/73175.
Повний текст джерелаThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 117-136).
In this thesis, I implemented a method for performing electronic structure calculations, "Constrained Density Functional Theory-- Configuration Interaction" (CDFT-CI), which builds upon the computational strengths of Density Functional Theory and improves upon it by including higher level treatments of electronic correlation which are not readily available in Density-Functional Theory but are a keystone of wavefunction-based electronic structure methods. The method involves using CDFT to construct a small basis of hand-picked states which suffice to reasonably describe the static correlation present in a particular system, and efficiently computing electronic coupling elements between them. Analytical gradients were also implemented, involving computational effort roughly equivalent to the evaluation of an analytical Hessian for an ordinary DFT calculation. The routines were implemented within Q-Chem in a fashion accessible to end users; calculations were performed to assess how CDFT-CI improves reaction transition state energies, and to assess its ability to produce conical intersections, as compared to ordinary DFT. The analytical gradients enabled optimization of reaction transition-state structures, as well as geometry optimization on electronic excited states, with good results.
by Benjamin James Kaduk.
Ph.D.
Watson, Mark Adrian. "Density-functional theory and molecular properties." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615929.
Повний текст джерелаSchenk, Stefan. "Density functional theory on a lattice." kostenfrei, 2009. http://d-nb.info/998385956/34.
Повний текст джерелаYasuda, Koji. "Correlation energy functional in the density-matrix functional theory." American Physical Society, 2001. http://hdl.handle.net/2237/8742.
Повний текст джерелаHelbig, Nicole. "Orbital functionals in density-matrix- and current-density-functional theory." [S.l.] : [s.n.], 2006. http://www.diss.fu-berlin.de/2006/442/index.html.
Повний текст джерелаWlodarczyk, Radoslaw Stanislaw. "Surface structure predictions and development of global exploration tools." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17207.
Повний текст джерелаThis work is a contribution in the field of theoretical chemistry and surface science. The joint computational and experimental studies investigated the atomic structure of ultrathin silica and iron-doped silica films formed on the Ru(0001) surface and water films formed on the MgO(001) surface. The atomic structure models were obtained using either the educated guess approach or the genetic algorithm that was designed and implemented within the DoDo package. The properties simulated for the resulting models are in a very good agreement with the experimental data (scanning tunnelling microscopy, infrared spectroscopy). The successful structure determination using the DoDo program shows that the genetic algorithm technique is capable of systematic and extensive exploration of the energy landscapes for 2D-periodic systems.
Osorio, Guillén Jorge Mario. "Density Functional Theory in Computational Materials Science." Doctoral thesis, Uppsala University, Department of Physics, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4496.
Повний текст джерелаThe present thesis is concerned to the application of first-principles self-consistent total-energy calculations within the density functional theory on different topics in materials science.
Crystallographic phase-transitions under high-pressure has been study for TiO2, FeI2, Fe3O4, Ti, the heavy alkali metals Cs and Rb, and C3N4. A new high-pressure polymorph of TiO2 has been discovered, this new polymorph has an orthorhombic OI (Pbca) crystal structure, which is predicted theoretically for the pressure range 50 to 100 GPa. Also, the crystal structures of Cs and Rb metals have been studied under high compressions. Our results confirm the recent high-pressure experimental observations of new complex crystal structures for the Cs-III and Rb-III phases. Thus, it is now certain that the famous isostructural phase transition in Cs is rather a new crystallographic phase transition.
The elastic properties of the new superconductor MgB2 and Al-doped MgB2 have been investigated. Values of all independent elastic constants (c11, c12, c13, c33, and c55) as well as bulk moduli in the a and c directions (Ba and Bc respectively) are predicted. Our analysis suggests that the high anisotropy of the calculated elastic moduli is a strong indication that MgB2 should be rather brittle. Al doping decreases the elastic anisotropy of MgB2 in the a and c directions, but, it will not change the brittle behaviour of the material considerably.
The three most relevant battery properties, namely average voltage, energy density and specific energy, as well as the electronic structure of the Li/LixMPO4 systems, where M is either Fe, Mn, or Co have been calculated. The mixing between Fe and Mn in these materials is also examined. Our calculated values for these properties are in good agreement with recent experimental values. Further insight is gained from the electronic density of states of these materials, through which conclusions about the physical properties of the various phases are made.
The electronic and magnetic properties of the dilute magnetic semiconductor Mn-doped ZnO has been calculated. We have found that for an Mn concentration of 5.6%, the ferromagnetic configuration is energetically stable in comparison to the antiferromgnetic one. A half-metallic electronic structure is calculated by the GGA approximation, where Mn ions are in a divalent state leading to a total magnetic moment of 5 μB per Mn atom.
Sargolzaei, Mahdi. "Orbital Polarization in Relativistic Density Functional Theory." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1167841057730-69007.
Повний текст джерелаAkyar, Ozge. "Density Functional Theory For Trapped Ultracold Fermions." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610948/index.pdf.
Повний текст джерелаrescaled interaction strength, dipole-dipole energy and the trap parameter which determine the trap geometry based on this theory. The thesis starts with a brief outline of the density functional theory and theory of our system, continues with calculations based on this theory, which are free of any variational assumptions for the density profile. Moreover, results of density graphics for harmonic trap will be followed by discussion of comparison and contrast with Thomas-Fermi method based on the paper of Goral et al.. These discussions are mainly about the shape of the density distribution, variation of the cloud parameters and energy behaviours according to the rescaled interaction strength. The thesis concludes with an analysis of contribution of density functional theory to this fermionic system.
Pawluk, Tiffany. "Iridium nanoparticles : a density functional theory study /." Available to subscribers only, 2005. http://proquest.umi.com/pqdweb?did=1075692711&sid=20&Fmt=2&clientId=1509&RQT=309&VName=PQD.
Повний текст джерелаOsorio, Guillén Jorge Mario. "Density functional theory in computational materials science /." Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4496.
Повний текст джерелаChoudhury, Rathin. "Application and development of density functional theory." Thesis, University College London (University of London), 2006. http://discovery.ucl.ac.uk/1444572/.
Повний текст джерелаYam, Chi-yung, and 任志勇. "Linear-scaling time-dependent density functional theory." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31246199.
Повний текст джерелаStauffert, Oliver [Verfasser], and Michael [Akademischer Betreuer] Walter. "Electron-phonon coupling with density functional theory." Freiburg : Universität, 2019. http://d-nb.info/1191689328/34.
Повний текст джерелаConroy, Michael W. "Density Functional Theory Studies of Energetic Materials." Scholar Commons, 2009. http://scholarcommons.usf.edu/etd/3691.
Повний текст джерелаNair, Nikhil. "New directions in hybrid density functional theory." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620224.
Повний текст джерелаHollins, Thomas William. "Local exchange potentials in density functional theory." Thesis, Durham University, 2014. http://etheses.dur.ac.uk/10932/.
Повний текст джерелаZawadzki, Krissia de. "Density-functional theory for single-electron transistors." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-24102018-165237/.
Повний текст джерелаO estudo de propriedades de transporte em dispositivos nano estruturados e junções moleculares tornou-se um tópico de grande interesse com a recente demanda por novas tecnologias quânticas. Grande parte do nosso conhecimento tem sido guiado por trabalhos experimentais e teóricos de um dispositivo conhecido como transístor de um elétron (SET), o qual é constituído por um ponto quântico acoplado a dois gases de elétrons independentes. O SET é particularmente interessante devido as suas propriedades de transporte a baixas temperaturas, as quais são governadas pelo efeito Kondo. Uma dificuldade metodológica, no entanto, tem barrado novos avanços teóricos para se obter uma descrição precisa de dispositivos realistas. Por um lado, a teoria do funcional da densidade (DFT), uma das ferramentas mais convenientes para calcular a estrutura eletrônica de materiais complexos, provê uma descrição apenas qualitativa das propriedades de transporte de transístores quânticos a baixas temperaturas. Por outro lado, uma descrição quantitativa satisfatória do SET a baixas temperaturas, tal como a modelagem e solução do modelo de Anderson via métodos exatos, é incapaz de levar em conta características realistas de dispositivos complexos, tal como geometria, estrutura de bandas e interações inter eletrônicas nos gases de elétrons. Embora a DFT os descreva bem, ela é inadequada para tratar correlações introduzidas pelo ponto quântico. Na presente tese propomos uma alternativa para este dilema. Nossa contribuição é fundamentada em conceitos de grupo de renormalização (RG). Especificamente, mostramos que, em condições de interesse experimental, os regimes de altas e baixas temperaturas em um SET correspondem aos pontos fixos de acoplamento fraco e forte do Hamiltoniano de Anderson. Baseando-nos em na análise do RG, mostramos que, no ponto fixo de baixas temperaturas, o emaranhamento entre a impureza e os spins dos gases eletrônicos introduz correlações não-locais que não podem ser descritas com abordagens DFT baseadas em aproximações locais ou quase locais para o potencial de troca e correlação. Em contraste, o ponto fixo de acoplamento fraco pode ser descrito por aproximações locais. Com o objetivo de obter uma descrição realista das propriedades de transístores quânticos, propomos um procedimento auto-consistente que começa do ponto fixo de acoplamento fraco e se aproveita de um método numérico eficiente para levar o Hamiltoniano para o ponto fixo de acoplamento forte. Nossa abordagem emprega DFT para tratar o sistema no limite de acoplamento fraco e o método de Grupo de Renormalização Numérico (NRG) para obter propriedades no regime de acoplamento forte. Como ilustração, aplicamos o procedimento para um transístor de um elétron modelado através do Hamiltoniano de Hubbard generalizado. Analisamos a dependência térmica da condutância no SET discutindo seu comportamento a baixas temperatura e comparamos nossos resultados com outras abordagens auto-consistentes e resultados experimentais.
Aarons, Jolyon. "Density functional theory applied to metallic nanoparticles." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/418013/.
Повний текст джерелаSargolzaei, Mahdi. "Orbital Polarization in Relativistic Density Functional Theory." Doctoral thesis, Technische Universität Dresden, 2006. https://tud.qucosa.de/id/qucosa%3A24939.
Повний текст джерелаJohnson, Erin R. "A density-functional theory including dispersion interactions." Thesis, Kingston, Ont. : [s.n.], 2007. http://hdl.handle.net/1974/926.
Повний текст джерелаWoodward, Clifford Edwin. "A density functional theory of polar fluids." Thesis, The University of Sydney, 1985. https://hdl.handle.net/2123/26797.
Повний текст джерелаSong, Yang. "Correcting density functional theory with supplemental potentials." Thesis, Boston University, 2013. https://hdl.handle.net/2144/12850.
Повний текст джерелаDensity Functional Theory (DFT) is a widely used method in quantum mechanics for modeling atoms and molecules. Commonly used DFT functionals have many shortcomings that include a poor description of dispersion, molecular geometries, exchange-repulsion, and hydrogen-bond interactions. To improve the quality of DFT, one popular idea is to apply empirical corrections to existing density functionals. Such an approach is both conceptually simple and computationally affordable. Despite many successful applications, most existing DFT empirical correction methods focus only on the dispersion corrections. In this thesis, we introduce system-specific empirical corrections to DFT. Our method not only provides corrections for dispersion, but also addresses problems such as deficiencies with molecular geometries, exchange-repulsion, and hydrogen bonding. The empirical correction, named "supplemental potential" (SP), is created by fitting the force differences between a functional and a high quality post-Hartree-Fock method. We tested the performance of SPs for three types of systems: water, methane-water, and molecular crystals. For the water system, the Becke-Lee-Yang-Parr (BLYP) functional description ofthe water potential energy surface (PES) can be improved to coupled-cluster quality with our water SP. For (H20)n (n=l-6), the relative cluster energies, cluster binding energies, and optimized energy structures are correctly predicted with the water SP correction. The developed methane-water SP is able to improve the BLYP PES to coupled-cluster quality in the study of methane water system. In the molecular crystal studies, the DFT-SP method correctly predict the most stable crystal structures among the sets of low-energy polymorphs, for four out of five studied organic molecules.
Sabatini, Riccardo. "Non-local correlation in Density Functional Theory." Doctoral thesis, SISSA, 2012. http://hdl.handle.net/20.500.11767/4710.
Повний текст джерелаKarlsson, Daniel. "Nuclear density functional theory calculations for the r-process nucleosynthesis : Nuclear density functional theory calculations for the r-process nucleosynthesis." Thesis, KTH, Fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-250775.
Повний текст джерелаDal, Corso Andrea. "Density-functional theory beyond the pseudopotential local density approach: a few cases studies." Doctoral thesis, SISSA, 1993. http://hdl.handle.net/20.500.11767/4059.
Повний текст джерелаSayin, Ceren Sibel. "Density Functional Theory Investigation Of Tio2 Anatase Nanosheets." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12611075/index.pdf.
Повний текст джерелаIusan, Diana Mihaela. "Density Functional Theory Applied to Materials for Spintronics." Doctoral thesis, Uppsala universitet, Materialteori, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-119887.
Повний текст джерелаMills, Eric A. "Protein-solvent interactions and classical density functional theory." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/55761.
Повний текст джерелаScience, Faculty of
Physics and Astronomy, Department of
Graduate
Manoli, Soheil Dimitri. "The generalized exchange local spin density-functional theory /." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75359.
Повний текст джерелаThe LSD GX exchange density is corrected for self-interaction (SI) by splitting the total Fermi hole correlation factor into pure-exchange and self-interaction holes.
These new LSD and SI corrected schemes are compared to each other. They also compare very well theoretically and numerically (total energies and eigenvalues) with other local schemes current in the literature.
New equations for the IP and electronegativities of the atoms in these local schemes are derived which give good results.
Zhou, Si. "Density functional theory study of oxidized epitaxial graphene." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52264.
Повний текст джерелаCrawford, P. "A density functional theory study of chemical reactivity." Thesis, Queen's University Belfast, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431588.
Повний текст джерелаBrincat, Nick. "Density functional theory investigation of the uranium oxides." Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.665418.
Повний текст джерелаIoannou, Andrew George. "Applications of time-dependent current density functional theory." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624734.
Повний текст джерелаDi, Sabatino Stefano. "Reduced density-matrix functional theory : correlation and spectroscopy." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30137.
Повний текст джерелаThis thesis addresses the description of electron correlation and spectroscopy within the context of Reduced Density-Matrix Functional Theory (RDMFT). Within RDMFT the ground-state properties of a physical system are functionals of the ground-state reduced density matrix. Various approximations to electron correlation have been proposed in literature. Many of them, however, can be traced back to the work of Müller, who has proposed an approximation to the correlation which is similar to the Hartree-Fock approximation but which can produce fractional occupation numbers. This is not always sufficient. Moreover, the expression of the observables of the system in terms of the reduced density matrix is not always known. This is the case, for example, for the spectral function, which is closely related to photoemission spectra. In this case there are error cancellations between the approximation to correlation and the approximation to the observable, which weakens the theory. In this thesis we look for more accurate approximations by exploiting the link between density matrices and Green's functions. In the first part of the thesis we focus on the spectral function. Using the exactly solvable Hubbard model as illustration, we analyze the existent approximations to this observable and we point out their weak points. Then, starting from its definition in terms of the one-body Green's function, we derive an expression for the spectral function that depends on the natural occupation numbers and on an effective energy which accounts for all the charged excitations. This effective energy depends on the one-body as well as higher-order reduced density matrices. Simple approximations to this effective energy give accurate spectra in model systems in the weak as well as strong-correlation regimes. To illustrate our method on real materials we calculate the photoemission spectrum of bulk NiO: our method yields a qualitatively correct picture both in the antiferromagnetic and in the paramagnetic phases, contrary to currently used mean-field methods, which give a metal in the latter case. The second part of the thesis is more explorative and deals with time-dependent phenomena within RDMFT. In general the time evolution of the reduced density matrices is given by the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy of equations, in which the equation of motion of the n-body reduced density matrix is given in terms of the (n + 1)-body reduced density matrix. The first equation of the hierarchy relates the one-body to the two-body reduced density matrix. The difficult task is to find approximations to the two-body reduced density matrix. Commonly used approximations are adiabatic extension of ground-state approximations. We explore this issue by looking at new approximations derived from Many-Body Perturbation Theory (MBPT) based on Green's functions as well as from the exact solution of the two-level Anderson impurity model in its ground state. Our first results on the two-level Anderson model subjected to various external fields show some interesting and, at the same time, puzzling features, which suggest to explore further these approximations
Rohra, Stefan Bruno. "Exact exchange Kohn-Sham spin current density functional theory." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=98054078X.
Повний текст джерелаNigussa, Kenate Nemera. "Density Functional Theory Investigations of Surface Structure and Reactivity." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14345.
Повний текст джерелаRebolini, Elisa. "Range-separated density-functional theory for molecular excitation energies." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066214/document.
Повний текст джерелаLinear-response time-dependent density-functional theory (TDDFT) is nowadays a method of choice to compute molecular excitation energies. However, within the usual adiabatic semi-local approximations, it is not able to describe properly Rydberg, charge-transfer or multiple excitations. Range separation of the electronic interaction allows one to mix rigorously density-functional methods at short range and wave function or Green’s function methods at long range. When applied to the exchange functional, it already corrects most of these deficiencies but multiple excitations remain absent as they need a frequency-dependent kernel. In this thesis, the effects of range separation are first assessed on the excitation energies of a partially-interacting system in an analytic and numerical study in order to provide guidelines for future developments of range-separated methods for excitation energy calculations. It is then applied on the exchange and correlation TDDFT kernels in a single-determinant approximation in which the long-range part of the correlation kernel vanishes. A long-range frequency-dependent second-order correlation kernel is then derived from the Bethe-Salpeter equation and added perturbatively to the range-separated TDDFT kernel in order to take into account the effects of double excitations
Tu, Guangde. "Studies of self-interaction corrections in density functional theory /." Stockholm : Bioteknologi, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4450.
Повний текст джерелаTu, Guangde. "Studies of Self-interaction Corrections in Density Functional Theory." Doctoral thesis, Stockholm : School of Biotechnology, Royal Institute of Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4740.
Повний текст джерелаZhang, Yu. "Mathematical aspects and chemical applications of density functional theory." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/5306.
Повний текст джерела