(178ad) All-Atom and United-Atom Simulations of Guanidinium-Based Ionic Liquids

All-atom
and United-atom Simulations of Guanidinium-based Ionic Liquids

Xiaomin Liu ^*,
Xiaochun Zhang, Xiaoqian Yao & Suojiang Zhang

State
Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering,
Chinese Academy of Sciences, 100190 Beijing, China

*Corresponding author (email: xmliu@home.ipe.ac.cn)

Ionic liquids (ILs) have been widely
used in separation, catalysis, electrochemistry and etc., and one of the most
outstanding characters is that ILs can be tailored and tuned for specific
tasks. In order to design and make better use of ionic liquids, the structures
and properties relationship is indispensable. Both molecular dynamics and Monte
Carlo simulations have been proved to be useful tools to understand the
behavior of molecules at the microscale and the thermodynamics properties of
the system. However, the quality of such simulations depends on the force field
parameters describing the interactions between atoms. All-atom (AA) or
united-atom (UA) force fields will be used due to the demand for more exact
results or the lower computational cost. In order to make an systematic
comparison between the two force fields, molecular simulations for four kinds
of acyclic guanidinium-based ionic liquids (cations: (R₂N)₂C=N+<,
anion: nitric or perchloric acid ) were performed based on the AA and the UA
force fields in this work. AA force field parameters were derived from our
previous work ^[1], and the UA parameters were proposed in this work.
Molecular dynamics simulation results using the AA and UA force fields were
compared. The simulated densities are very similar to each other. Center of
mass radial distribution functions (RDFs), site to site RDFs and spatial
distribution functions (SDFs) were also investigated to depict the microscopic
structures of the ILs.

Reference:

[1] X. Liu, G. Zhou, S. Zhang. Molecular dynamics
simulation of acyclic guanidinium-based ionic liquids. Fluid Phase Equilib.,
2008, 272: 1-7.

Acknowledgments

This work was supported by General Program Youth of
National Natural Science Foundation of China (20903098, 21106146) and State Key
Laboratory of Multiphase Complex Systems (MPCS-2011-D-05)