Submitted by Maike Costa (maiksebas@gmail.com) on 2016-03-15T13:17:25Z No. of bitstreams: 1 arquivototal.pdf: 5498676 bytes, checksum: 4a307b30b2c4f45e565cf9923519ec7f (MD5) / Made available in DSpace on 2016-03-15T13:17:25Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 5498676 bytes, checksum: 4a307b30b2c4f45e565cf9923519ec7f (MD5) Previous issue date: 2015-02-20 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Investigating the stability and electronic structure of nanomaterials is essential for their application in electronic devices. In this thesis were analysed two types of nanostructures, a derivative of h-BN and the other of graphene. This analysis was performed using first-principles calculations by Density Functional Theory (DFT), implemented by the SIESTA code. First we investigated two kinds of stacks of h-BN bilayer with impurities and by means of the calculation of interaction and formation energies was identified the most stable bilayers, both due to the nature of the stack and to the type impurity introduced. We also note that the combination of these two effects cause considerable variations in the gaps of energy and impurity. We also use an electric field perpendicular to the plane of the bilayer and observe different changes in the electronic structure related to the permanent electric dipole moment of each nanostructure. The second nanomaterial investigated in this work, the Carbon bicones have been proposed based on the experimental observation of nanocones. The possibility of bicones are experimentally obtained was analyzed by comparing the stability of these nanostructures with existing cones. It was found that some of them are as stable as the cones, which, at least theoretically, enables the synthesis of these nanomaterials. The effect of the electric field and impurities on the electronic structure of bicones were also analyzed, resulting in significant changes in the state density, evidenced by the emergence of new states near the Fermi level / Investigar a estabilidade e a estrutura eletrônica dos nanomateriais é imprescindível para a aplicação dos mesmos em dispositivos eletrônicos. Nesta tese foram analisados dois tipos de nanoestruturas, uma derivada do h-BN e a outra do grafeno. Tal análise foi realizada utilizando cálculos de primeiros princípios, através da Teoria do Funcional da Densidade (DFT), implementados pelo código SIESTA. Primeiramente investigamos dois tipos de empilhamentos de bicamadas de h-BN com impurezas e por meio das energias de interação e formação calculadas, identificamos as bicamadas mais estáveis, tanto em função da natureza do empilhamento, quanto em relação ao tipo de impureza introduzida. Constatamos também que a combinação destes dois efeitos, causa consideráveis variações nos gaps de energia e de impureza. Aplicamos ainda um campo elétrico perpendicular ao plano das bicamadas e observamos diferentes modificações na estrutura eletrônica, relacionadas ao momento de dipolo elétrico permanente de cada nanoestrutura. O segundo nanomaterial investigado neste trabalho, os bicones de Carbono, foram propostos tomando por base a constatação experimental dos nanocones. A possibilidade dos bicones serem obtidos experimentalmente foi analisada comparando a estabilidade destas nanoestruturas com a dos cones já existentes. Foi possível constatar que alguns deles são tão estáveis quanto os cones, o que, ao menos teoricamente, viabiliza a sintetização destes nanomateriais. O efeito do campo elétrico e das impurezas sobre a estrutura eletrônica dos bicones também foram analisados, resultando em mudanças relevantes na densidade de estado, evidenciadas através do surgimento de novos estados próximos ao nível de Fermi.

We present a study of high-resolution long-slit spectra of the Narrow-Line Regions (NLRs) of NGC 4151 (a Seyfert 1 galaxy) and NGC 1068 (a Seyfert 2 galaxy) obtained with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope (HST). The spectra were retrieved from the Multimission Archive at Space Telescope (MAST) and were obtained from five and seven orbits of HST time resulting in five and seven parallel slit configurations at position angles of 52 degrees and 38 degrees for NGC 4151 and NGC 1068 respectively. The spectra have a spatial resolution of 0.2 arcsecond across and 0.1 arcsecond along each slit. Observations of [O III] emission from the NLRs were made using the medium resolution G430M grating aboard HST. The spectral resolving power of the grating, R~9000, resulted in the detection of multiple kinematic components of the [O III] emission line gas along each slit. Radial velocities of the components were measured using a Gaussian fitting procedure. Biconical outflow models were generated to match the data and for comparison to previous models done with lower dispersion observations. The general trend is an increase in radial velocity roughly proportional to distance from the nucleus, followed by a linear decrease after roughly 100 pc. This is similar to that seen in other Seyfert galaxies, indicating common acceleration and deceleration mechanisms. The full-width at half-maximum (FWHM) of the emission lines reaches a maximum of 1000 km/s near the nucleus, and generally decreases with increasing distance to about 100 km/s in the extended narrow-line region (ENLR), starting at about 400 pc from the nucleus. In addition to the bright emission knots, which generally fit our model, there are faint high velocity clouds that do not fit the biconical outflow pattern of our kinematic model. A comparison of our observations with high-resolution radio maps shows that the kinematics of the faint NLR clouds may be affected by the radio lobes that comprise the inner jet. However, the bright NLR clouds show a smooth transition across the radio knots in radial velocity and velocity dispersion plots and remain essentially undisturbed in their vicinity, indicating that the radio jet is not the principal driving force on the outflowing NLR clouds. A dynamical model was developed for NGC 1068; it includes forces of radiation pressure, gravity, and drag due an ambient medium, simultaneously acting on the NLR clouds. The velocity profile from this model was too steep to fit the data, which show a more slowly increasing velocity profile. Gravity alone was not able to slow down the clouds but with the drag forces included, the clouds could slow down, reaching systemic velocities at distances that depend on the column densities of the NLR gas and density of the intercloud medium. A biconical model using the geometric parameters from our kinematic fit, and the velocity law from the dynamic fit, was used to match the data. The resulting dynamic model represented a poor fit to the data, indicating the need for additional dynamical considerations.