Propriedades eletrônicas e estruturais de clusters metálicos via métodos ab initio

• Autor(a) principal: Damasceno Junior, Jose Higino
• Data de Publicação: 2015
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• dARK ID: ark:/38995/00130000091zz
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/4846
• topic: Monte Carlo quântico de difusão; Cluster metálicos; Aromáticos; Energia de correlação eletrônica; Potencial de ionização; Afinidade eletrônica; Diffusion quantum Monte Carlo; Metal cluster; Aromatics; Electron correlation energy; Ionization potential; Electron affinity; FISICA::FISICA GERAL

Clusters systems are very different from molecules or their bulk materials, since they exhibit many specific properties. As example, the bond in metallic clusters of metallic atoms is intermediate between metallic and covalent bonding. In general, the structural and electronic properties of these systems are very difficult to measure experimentally, and therefore theoretical modeling is very important in characterizing them. In this thesis, we employed ab initio methods to study metallic clusters such as the aluminum hydride clusters as well as a few aromatic metal clusters. The optimized geometries of the studied clusters have been determined using DFT. The electronic structures of these systems were investigated using the QMC methods. The calculations were carried out within the Variational (VMC) and fixed-node diffusion (DMC) quantum Monte Carlo methods. The calculations are also performed in the Hartree-Fock (HF) approximation in order to analyze the impact of electron correlation. With regards the aluminum hydride clusters, the total atomic binding energy impact varies from ~20% up to about ~50%, whereas for the electron binding energy it ranges from ~1% up to ~73%. The decomposition of the electron binding energies clearly shows that both charge redistribution and electron correlation are important in determining the detachment energies, whereas electrostatic and exchange interactions are responsible for the ionization potential. For the aromatic metal clusters, the presence of a dopant plays important role in their electronic properties enhancing their binding energy, electron affinity, hardness and resonance energy.