Propriedades eletrônicas e estruturais de clusters metálicos via métodos ab initio
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Data
2015-09-25
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Universidade Federal de Goiás
Resumo
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.
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Citação
HIGINO DAMASCENO, J. Propriedades eletrônicas e estruturais de clusters metálicos via métodos ab initio. 2015. 178 f. Tese (Doutorado em Física) - Universidade Federal de Goiás, Goiânia, 2015.