Characterization of the solvation dynamics of an ionic liquid via molecular dynamics simulation

Kobrak, Mark N.

doi:doi:10.1063/1.2227026

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Quantized time correlation function approach to nonadiabatic decay rates in condensed phase: Application to solvated electrons in water and methanol

A new, alternative form of the golden rule formula defining the nonadiabatic transition rate between two quantum states in condensed phase is presented. The formula involves the quantum time correlation function of the energy gap, of the nonadiabatic coupling, and their cross terms. Those quantities can be inferred from their classical counterparts, determined via molecular dynamics simulations. The formalism is applied to the problem of the nonadiabatic p→s relaxation of an equilibrated p-elec...

On the role of frustration on the glass transition and polyamorphism of mesoscopically heterophase liquids

The model of heterophase fluctuations is developed accounting frustration of the mesoscopic solidlike fluctuons. Within the framework of this model, the glass transition and polyamorphous transformations are considered. It is shown that the frustration increases the temperature range in which the heterophase liquid state exists. the upper and lower boundaries of this temperature range are determined. These boundaries separate different phase states—amorphous solid, heterophase liquid, and fluid...

The solvation dynamics of ionic liquids have been the subject of intense experimental study but remain poorly understood. We present the results of molecular dynamics simulations of the solvation dynamics of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate in response to photoexcitation of the fluorescent dye coumarin-153. We reproduce the time-resolved fluorescence Stokes shift using linear response theory, then use novel statistical techniques to analyze cation and anion contributions to the signal. We find that the solvation dynamics are dominated by collective ionic motion and characterize the time scale for various features of the collective response. Further, we use the Steele analysis [ Mol. Phys. 61, 1031 (1987) ] to characterize the contributions to the observed Stokes shift made by translational and rovibrational degrees of freedom. Our results indicate that in contrast to molecular liquids, the rovibrational response is trivial and the observed fluorescence response arises almost entirely from ionic translation. Our results resolve previously open questions in the literature about the nature of the rapid dynamics in room-temperature ionic liquids and offer insight into the physical principles governing ionic liquid behavior on longer time scales.

Article Outline

INTRODUCTION
METHODOLOGY
1. Molecular dynamics
ANALYSIS
1. Calculation of the absorption spectrum
2. Linear response theory and the time correlation function
3. Component time correlation function
4. Single-ion/ion-pair correlation functions for CTCFs
5. Steele analysis
CONCLUSIONS

ERRATUM

Erratum: “Characterization of the solvation dynamics of an ionic liquid via molecular dynamics simulation” [J. Chem. Phys. 125, 064502 (2006)]
Mark N. Kobrak
J. Chem. Phys. 127, 099903 (2007)JCPSA6000127000009099903000001

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KEYWORDS and PACS

Keywords

organic compounds, dyes, liquids, molecular dynamics method, solvation, photoexcitation, fluorescence

PACS

61.25.Em

Molecular liquids
61.20.Ja

Computer simulation of liquid structure

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http://link.aip.org/link/doi/10.1063/1.2227026

PUBLICATION DATA

ISSN:

0021-9606 (print)

1089-7690 (online)

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American Institute of Physics

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