ELECTRONIC STATES IN THE SOLID

Author: OGANDO ARREGUI EDUARDO.
Year: 2004.
University: PAÍS VASCO [www.ehu.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: The study of the mechanisms that control the stability of matter at the nano-scale proves to be crucial to manufacture atomic scale organized structures for applications in nanodispositivos. At this level, comportament quantum undoubtedly plays a role, so that the properties of these systems are not scalable respect to macroscopic behavior. In this dissertation we have focused on the stability of nanohilos and nanoislas metal, calculating their energy through the theory of functional density (DFT). We used simple models, such as "jellium" significantly simplify the problem, as they believe ions as a homogeneous continuous positive charge, but on the other hand can obtain important conclusions about trends in the performance of these systems. The study nanohilos metal is motivated by experiments with the technique MCBJ (Mechanically controllable break junction), which can study the geometries of manohilos formed along with other mechanical properties and transport. We have placed special emphasis on durable solutions or magic rays. Part of the nanoislas or wafers ultrafine is motivated by experiments on STS (Scanning tunneling spectroscopy) on islands of flooding on Pb Cu (111), which has proven the existence of certain thickness of islands that are particularly stable. We have explained the existence of these magical islands and on the other hand we have analyzed the problem of determining the containment barrier.

Author: FERNANDEZ RODRIGUEZ JAVIER.
Year: 2005.
University: OVIEDO [www.uniovi.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: In this paper, has conducted an analysis of diffraction data resonant x-ray utiliando a model for atomic detection systems and multipole magnetic moments. The materials studied are: a) the compound GdB4 b) the system metal-aislante V2 O3. In the case of material GdB4, the intensities of resonant x-ray diffraction are analyzed in terms of potential magnetic configurations, taking into basin possible structural phase transitions to different groups of space group space high temperature. The order parameter of the transition cuadrupolar is already identified adjustments from the intensities calculated for the data available is derived parameter that relates the time cuadrupolar with the magnetic moment. It also concludes that the symmetry of the material allows the effect magnetoeléctrico. Moreover, it was predicting the outcome of a possible diffraction experiment magnetic resonant not in a sample of powder compound GdB4. The system metal-aislante V2O3 intensities measures are adjusted to the combination of the intensities E2 and E1-E2. The parameters give information about atomic moments octupolar and anapolar of atoms vanadio.También there has been a search for the most appropriate reflections to conduct a new experiment that would provide a better understanding of the contributions of type E1-E2 to intensity, and better estimation of the parameters related to the atomic time anapolar

Author: VARSANO DANIELE.
Year: 2005.
University: PAÍS VASCO [www.ehu.es].
Place of defense: FACULTAD DE QUÍMICA.
Place of preparation: FACULTAD DE QUÍMICA.

Summary: This thesis presents theoretical studies of the optical properties of systems of low dimensionality. The work deals with both theoretical developments formalism response to external fields as applications to polymers, biomolecules and surfaces. The thesis has been divided into three parts. In a first described the two theoretical frameworks used: 1-functional theory of the time-dependent density (TDDFT). 2 - The theory of disturbance of many bodies (MBPT). And we develop in detail the possibilities of connecting the two theories. The second part describes the numerical algorithms and implementations used in the calculations and contributions of our original work on the development of computational techniques. The last part presents the results for different systems. By the theory of functional density dependent on the time has been studying the optical response of biomolecules with potential technological application. The results explain the experiments with great precision. With the same technique, we analyzed the response of nearly one-dimensional systems (polymer). For this type of system performance with standard functional results are very bad and we have developed a new theory based on the functional disturbance of many bodies. In the final chapters setting out a new method for treating problems fotoemisión under the TDDFT allowing describe non-linear effects: this technique has been applied to the process of fotoemisión two photons on the surface of copper.