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.
Results
Showing 1 to 20 of 51 for “"electron correlation"”.
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Electron Correlation Studies of Weakly Bonded Systems
… is found to be chemically bonded due to the correlation effects of the d orbitals.
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New ab initio formulation of electron correlation and spin resonance
… of single-particle operators. Representing correlations by a single tensor product leads to the recently proposed "natural orbital functional." We show that this theory is no more accurate than Hartree-Fock in describing the homogeneous electron gas for the range of densities typically found …
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A photoemission study of quasiparticle excitations, electron-correlation effects and magnetization dynamics in thin magnetic systems
This thesis is focused on the electronic, spin-dependent and dynamical properties of thin magnetic systems. Photoemission-related techniques are combined with synchrotron radiation to study the spin-dependent properties of these systems in the energy and time domains. In the first part of this …
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Rigorous Studies of the Electronic Structures of Molecules and Molecular Complexes. Electron Correlation Effects in the Hydrogen Bonding of Small Dimeric Systems (Hydrogen Fluoride, Carbon Monoxide, Nitrogen, Hydrogen Cyanide)
The effects of electron correlation in the weakly interacting dimers of hydrogen fluoride with the nitrogen molecule, carbon monoxide and hydrogen cyanide are presented. While linear equilibrium structures are found for these complexes, an attempt is made to elucidate their vibrationally averaged …
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Correlated electron transport across atomic and molecular tunnel junctions
… to miniaturise the importance of describing electronics on an atomic scale increases. A molecular junction consists of a molecule connected to to metal electrodes via linker molecules and may be thought of as the prototype system for electronics on a few nanometre length scale. For charge …
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Advances in Multiconfiguration Pair Density Functional Theory and Applications to Excited State, Singlet-Triplet Gaps and Magnetism
… atoms and molecules such as excitation energies, electronic spectra, magnetism, characterization of chemical bonds, catalysis etc. It is therefore important to be able to correctly describe the interactions between electrons, also known as electron correlation, whose description is a major …
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Development and Efficient Implementation of Electron-Hole Interaction Kernel for Investigation of Electronic Excitations in Semiconductor and Metallic Nanoparticles
… on efficient theories that allow for capturing electron-correlation in semiconductor or metallic nanoparticles. These systems are computationally challenging due to the size of the systems, the number of electrons per atom, and the degeneracy of the particle-hole states. Three methods presented …
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Electronic and Spin Correlations in Asymmetric Quantum Point Contacts
… point contact (QPC) is a quasi-one dimensional electron system, for which the conductance is quantized in unit of $2e^2/h$. This conductance quantization can be explained in a simple single particle picture, where the electron density of states cancels the electron velocity to a constant. …
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On Symmetry of Multiple Self-Consistent-Field Hartree–Fock Solutions
… especially true for systems containing unpaired electrons, or electrons with high angular momenta, or both, in which many low-lying HF solutions can be located. However, there has not been much concerted effort to analyse these solutions systematically to understand their behaviours and harness …
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Simulations of laser-induced correlated many-electron dynamics in molecular systems
In this thesis, simulations of laser-driven many-electron dynamics in molecules are presented, i.e., the interaction between molecules and an electromagnetic field is demonstrated. When a laser field is applied to a molecular system, a population of higher electronic states takes place as well as …
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The Unreasonable Usefulness of Approximation by Linear Combination
… to reduce the computational cost of accurate electronic structure calculations to linear. Meaning, that the total time to solution for the calculation grows at the same rate as the number of particles that are correlated. Multiple techniques for exploiting data-sparsity are discussed, with a …
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Muonium in C₆₀ fullerites : studies of structural and electronic properties
… model of doped fullerites indicating that electron-electron correlation effects may be important in determining the electronic structure of these solids.
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Photophysics of carbon nanotubes
… of single-wall carbon nanotubes. Studying the electronic and vibrational properties of carbon nanotubes, we find that carbon nanotubes less than 1 nm in diameter exhibit dramatic changes in their electron and phonon dispersion relations due to the curvature of the nanotube sidewall and the …
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A polarized helium ion beam for surface electronic structure studies
… ion beam suitable for use as a- probe of surface electronic structure of metals. The method would represent an extension of ion neutralization spectroscopy (INS), and should provide new information on surface magnetism, electron correlation effects, and the dynamics of the ion neutralization …
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Electronic properties of diamond and silicon
Hartree-Fock electron energy bands for Silicon have been obtained, and the energy dependent imaginary part of the dielectric constant has been obtained from the theoretical Hartree-Fock results. These theoretical results are compared with experimental data and other theory. It is found that this is …
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Models for transition metal oxides and for protein design
… when using these methods for predicting the electronic structure and total energy of transition metal oxides. We demonstrate that the LDA+U method, in which localized d electrons are treated with a Hubbard-like model, gives considerably better predictions in band gap, magnetization, lattice …
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Challenging systems for quantum chemistry : inorganic excited states and intermolecular aggregates
… of quantum chemistry, mostly due to strong correlation, degeneracy and near-degeneracy problems, in addition to a large density of states. A calibration study of the electronic excited states of a range of complexes has been carried out in a number of chapters using a wide range of methods. …
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Quantum Monte Carlo study of correlated electronic systems
Describing correlated electron systems has been a major challenge in computational condensed-matter physics. Quantum Monte Carlo, a powerful computational tool for the study of correlated systems, solves electron correlation problems explicitly. It has been taken as a benchmark method for …
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Accelerating and Converging Stochastic Quantum Chemistry
… levels up to CCSDTQ5 was tested on the uniform electron gas, a model solid system, for various degrees of electron correlation. This gave information on what coupled cluster level is needed to reach sufficient accuracy when modelling a solid system. Before large solid systems can be modelled, …
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