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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 46 for “"density approximation."”.
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Study of Ultracold Fermi Gases in the BCS-BEC Crossover: Quantum Monte Carlo Methods, Hydrodynamics and Local Density Approximation.
… number of particles, a fruitful combined use of Density Functional Theory (DFT) and QMC is necessary. The study of the dynamics of ultracold gases has received little attention with QMC techniques, due to the intrinsic computational difficulty of the many-body problem, so that general …
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Particle shape corrections to Twersky's formalism for multiple scattering in a random particulate medium
… applications of Twersky’s work use a far-field approximation and a point-particle assumption. At high frequencies, particle sizes may be large relative to a wavelength; therefore, the point-particle assumption is inaccurate. Under a low-density approximation, this thesis introduces a scattering …
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Electronic Structure in the Organic-based Magnet [Feᴵᴵ(TCNE)(NCMe)₂][FeᴵᴵᴵCl₄] using the Orthogonalized Linear Combination of Atomic Orbitals Method with Hubbard U
… Atomic Orbitals (OCLAO) methods. The Local Spin Density Approximation (LSDA) method plus the Hubbard U parameter is used to account for on-site atomic Coulombic repulsion and exchange correlation interactions for the d orbitals of the FeII atoms. Applying the Hubbard U parameter results in an …
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Theory of density functionals
<p>Density functional theory is an alternative quantum mechanical theory that offers simple ways of performing calculations of the electronic properties of matter. Many different methods derive from density functional theory. The most appealing for its simplicity and rigor is the theory of Kohn and …
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The development of a local orbital method and its applications to aluminum and platinum clusters
… on the ab initio Harris functional of the local density approximation of density functional theory, by adding d orbitals into the original local orbital basis set of $sp\sp3$ orbitals. This enables the treatment of most elements in the periodic table including all $sp\sp3$ bonding elements and …
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Temperature dependent structural, electronic and optical properties of the Si(100) surface from first principles
… presented here were obtained using the local density approximation (LDA) to density functional theory (DFT), within the pseudo-potentials scheme. We present the results of the numerical simulations for the Si bulk and Si(100) surface; ab-initio molecular dynamics (AIMD) using the …
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Ab initio Beschreibung der elektronischen Struktur und der Transporteigenschaften von metallischen Nanodrähten
… are presented. The calculations are based on density functional theory in local density approximation using a Screened Korringa-Kohn-Rostoker-Green's function method. The method was extended for the description of quasi-onedimensional systems. Translational invariance in direction of the wire …
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Computer Modeling of Silicon Quantum Dot Floating -Gate Flash Memory Devices
… (3-D) Poisson and Kohn-Sham equations within the density functional formalism, where the quantum many-body interactions are treated according to the local-density approximation. We investigate the quantum-dot electronic structure, device capacitance-voltage characteristics and derive the threshold …
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Computational modelling of the electronic and structural properties of chalcopyrite-type semiconductors and platinum group metal chalcogenides
… gaps. Electronic structure calculations based on Density Functional Theory (DFT) have been extensively used to study and to describe such properties of many condensed matter systems. In this work, we have utilized DFT to study the electronic properties of eight chalcopyrite-type semiconductors …
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Besetzte und unbesetzte elektronische Struktur von geordneten Dünnschichtverbindungen der Seltenen Erden Eu und Yb mit den Übergangsmetallen Pd und Ni
… is in good accordance with results of local-density-approximation band-structure calculations.
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Advances in Copula Estimation and Distribution Theory
… results related to copulas. Four distinct copula density estimation methodologies, including Bernstein’s polynomial approximation, are proposed and criteria for the selection of their tuning parameters are provided. These four approaches were found to produce similar density estimates, which …
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Simulation of Single -Electron Charging Effects in Planar Nanoscale Devices
… incorporate electron spin under the Local Spin Density Approximation, the charging properties of the double quantum dot are investigated in terms of electron spin and interdot interaction. It is shown that both electrostatic and quantum mechanical coupling between the dots affect the charging …
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Quasi-condensation in low-dimensional Bose gases
… is possible, which exhibits suppressed density fluctuations, but whose phase fluctuates strongly. It is shown that modified mean-field theories based on a symmetry-breaking approach can even characterise phase coherence properties of such a quasi-condensate properly. A correct …
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Spin waves in doped graphene
… waves are described using time-dependent spin-density-functional response theory, treating dynamical xc effects within the Slater and Singwi-Tosi-Land-Sjolander approximations. We obtain spin-wave dispersions and spin stiffnesses as a function of doping and spin polarization, and discuss …
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Tunneling spectroscopy of highly ordered organic thin films
… of the Landauer transport formalism with a density-functional-parametrized tight-binding scheme within the Local Density Approximation (LDA) as well as semiempirical quantum chemistry calculations.
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Magnetism, Structure and their Interactions
… categories of compounds are investigated by density functional calculations under local spin density approximation (LSDA). The first compound is Rh2MnGe with full Heusler structure at ambient condition. However, the structure is unstable at T=0 according to our calculations. A more stable …
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Modeling Temperature Effects on Vector-Borne Disease Dynamics
… Next, I use these traits to model mosquito density, and then I incorporate the density into our mathematical models to investigate the effect it has on the basic reproductive ratio R0, a measure of how contagious the disease is. I use R0 to determine disease risk. For dengue, my results show …
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MICROSCOPIC THEORY OF INFINITE NUCLEAR MATTER AND NON-EMPIRICAL ENERGY FUNCTIONALS
Nuclear density functional theory (DFT) and ab initio theory are complementary approaches to nuclear structure. DFT can be applied to the whole nuclear chart, but relies on empirical energy density functionals (EDFs). As a consequence, predictions in regions where experimental data are lacking, …
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Analysis of Numerical Methods for Incompressible Multiphase Flows with Thermal Convection
… the temperature equation under the Boussinesq approximation. Unlike traditional schemes that rely on using the temperature and velocity as primary variables, our schemes use the momentum and internal energy. In addition, our schemes involve a semi-implicit projection method, which effectively …
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Quantum Monte Carlo: Applications of the Twist -Averaged Boundary Conditions and the Calculation of Forces
… Lande g factor. At the experimental equilibrium density of liquid 3He, we computed the spin polarization energy and found the unpolarized state is stable, in agreement with experiments. We also studied the electronic energy in a slab geometry using both density functional theory within the local …
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