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Doctoral Thesis
DOI
Document
Author
Full name
Vitor Hugo Paschoal
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2019
Supervisor
Committee
Ribeiro, Mauro Carlos Costa (President)
Autreto, Pedro Alves da Silva
Braga, Ataualpa Albert Carmo
Coutinho, Kaline Rabelo
Title in Portuguese
Dinâmica coletiva de líquidos iônicos
Keywords in Portuguese
Espectroscopia molecular
Espectroscopia Raman
Simulação de dinâmica molecular
Abstract in Portuguese
Neste trabalho foram exploradas a estrutura e a dinâmica coletiva de líquidos iônicos nas suas fases líquidas e nas fases vítreas combinando-se técnicas experimentais e computacionais. A partir de cálculos de química quântica para refinamento de parâmetros de campos de força, foram feitas simulações de dinâmica molecular clássica que permitiram caracterizar a estrutura de líquidos iônicos puros e soluções com Li+, obter as curvas de dispersão acústicas e ópticas além de parâmetros relaxacionais destes sistemas. Também foram utilizadas técnicas experimentais como espalhamento Brillouin de luz (na Universidade de Perugia) e de raios-X (no Advanced Photon Source, APS), difração de raios-X (no Laboratório Nacional de Luz Síncrotron, LNLS) e espectroscopia Raman (no Laboratório de Espectroscopia Molecular, LEM) para o estudo destes sistemas. A partir destes experimentos propriedades dinâmicas e estruturais dos líquidos iônicos através do seu diagrama de fases (em baixas temperaturas e altas pressões) foram obtidas e foi possível mostrar-se relações entre sua estrutura e dinâmica. Construindo sobre a teoria de Frenkel de fônons em líquidos, foi possível justificar diferentes aspectos da dinâmica coletiva de líquidos iônicos em nível microscópico, considerando tanto dados experimentais quanto dados de simulação. Ainda, analisando-se resultados experimentais sob a ótica desta teoria, foi possível obter-se uma nova perspectiva sobre a transição vítrea destes sistemas.
Title in English
Collective dynamics of ionic liquids
Keywords in English
Molecular dynamics simulation
Molecular spectroscopy
Raman spectroscopy
Abstract in English
In this work the structure and the collective dynamics of ionic liquids in their liquid and glassy phases in different points of their phase diagram was studied combining experimental and computational techniques. Starting from quantum chemistry calculations for force field parameter refinement, classical molecular dynamics simulations were performed, which allowed characterizing the structure of pure ionic liquids, as well as, their solutions with Li+. Furthermore, these systems optical and acoustic dispersion curves were obtained, as well as, relaxational parameters. Experimentally, techniques such as light and X-ray Brillouin scattering (performed at the University of Perugia and Advanced Photon Source, APS, respectively), X-ray diffraction (performed at the National Synchrotron Light Laboratory, LNLS) and Raman spectroscopy (performed at the Molecular Spectroscopy Laboratory, LEM) were employed to study these liquids. With these experiments, it was possible to study dynamical and structural properties of ionic liquids across their phase diagram (at low temperatures or high pressures). With the aid of Frenkels phonon theory of liquids, it was possible to justify different dynamical aspects of the dynamics of liquids, ground on microscopic observations from either simulations or experiments. Furthermore, by employing this theory to the analysis of experimental data, it was possible to obtain a new perspective related to the glass transition process of the studied samples.
 
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Publishing Date
2019-11-14
 
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