Dinâmica coletiva de líquidos iônicos

Abstract

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 Frenkel's 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.