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Molecular dynamics of ionic liquids: studies of time-domain ultra-fast spectroscopies

Grant number: 08/01035-4
Support type:Scholarships in Brazil - Post-Doctorate
Effective date (Start): September 01, 2008
Effective date (End): June 30, 2010
Field of knowledge:Physical Sciences and Mathematics - Chemistry
Principal Investigator:Munir Salomao Skaf
Grantee:Ary de Oliveira Cavalcante
Home Institution: Instituto de Química (IQ). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

Molecular dynamics simulations will be used to investigate dynamical processes in room temperature ionic liquids (IL). The fastest dynamical processes will be examined by means of appropriate response functions associated to ultra-fast time-domain spectroscopies such as time-dependent Stokes shift (solvation dynamics) and optical Kerr effect. The slow and highly correlated dynamics of IL, which resembles in many ways that of supercooled and glass forming liquids, will be investigated by looking at the underlying molecular mechanism responsible for the behavior of the characteristic transport coefficients.In addition to simulations using conventional nonpolarizable force fields, we seek to implement a polarizable model to describe more realistically the dynamics of IL up to tens of picoseconds of real dynamics. Among the phenomena of interest, are the ultra-fast relaxation of the collective polarizability time-correlations, which define the band contours in Kerr induced Raman spectra, and solvation dynamics responses. LIs are liquid environments that exhibit unusual solvation dynamics behavior which departs markedly from that of common organic solvents. We will investigate the role played by the micro-environment of the ionic species to the solvation dynamics around coumarin C153. The specific goals are:1. To perform MD simulations using nonpolarizable and polarizable force fields of C153 in IL.2. To improve available simulation models by (i) adopting an explicit all-atom description for the anionic species and (ii) implementation of a polarizable model for cationic and anionic species.3. To perform detailed analyses of the structural and dynamical properties of the solvent around C153 and to contribute to further understand the role of the cations and anions to the relaxationof the solvation response functions at short times.4. To identify changes in the simulated properties that characterize solvation dynamics of C153 in IL ambients.