Molecular dynamics simulations ionic fluids

S. Feng, G.A. Voth, Molecular dynamics simulations of imidaz-oHum-based ionic liqmdAvater mixtures Alkyl side chain length and anion effects. Fluid Phase Equilib. 294 (2010) 148-156. 

Liu, X., Zhou, G., Zhang, S. and Yao, X., Molecular dynamics simulation of dual amino-functionalized imidazolium-based ionic liquids. Fluid Phase Equilib. 284,44-49 (2009). 

Once the potential is chosen, Monte Carlo (MC) and molecular dynamics (MD) simulations form important tools for calculating phase equilibria [176]. With one notable exception [51], only MC techniques were employed. Methodological developments in MC techniques were addressed in a previous volume of this series [177], so that we summarize here only some aspects important for the treatment of ionic fluids. 

The study of fluid behavior in nano-conflnement is a relatively new research arena. The ratio of surface area to volume becomes extremely large at such small scales in which the non-dimensional Reynolds number Re is also typically low (< 1) and the flow remains laminar. Diaguji et al. [4] mention that, except for steric interactions, inter-molecular interactions like van der Waals force and electrostatic force can be modeled as continua. Specifically, the continuum dynamics is an adequate description of liquid transport for length scales higher than 5nm. In that context we aim to employ a hydrodynamic model to simulate ionic species transport through a 30 nm high nanofluidic channel with a reservoir upstream and a sink downstream. 

The theoretical framework in which it is possible to provide high quality studies of the microscopic structure of the ionic liquid is mainly represented by classical molecular mechanics and, only very recently, by ab-initio molecular dynamics. While the employed theoretical techniques are not very different from those used for conventional fluids, many difficulties arise because of the microscopic nature of ionic liquids. In particular these substances are extremely viscous and simulation times become quickly prohibitive if one wants to describe dynamical properties, even as simple as diffusion coefficients. Recent technological advances such as the introduction of GPU clusters might allow unprecedented possibilities in the simulation of these material opening the route to the simulation of rare events and long time scale phenomena. 

The several theoretical and/or simulation methods developed for modelling the solvation phenomena can be applied to the treatment of solvent effects on chemical reactivity. A variety of systems - ranging from small molecules to very large ones, such as biomolecules [236-238], biological membranes [239] and polymers [240] -and problems - mechanism of organic reactions [25, 79, 223, 241-247], chemical reactions in supercritical fluids [216, 248-250], ultrafast spectroscopy [251-255], electrochemical processes [256, 257], proton transfer [74, 75, 231], electron transfer [76, 77, 104, 258-261], charge transfer reactions and complexes [262-264], molecular and ionic spectra and excited states [24, 265-268], solvent-induced polarizability [221, 269], reaction dynamics [28, 78, 270-276], isomerization [110, 277-279], tautomeric equilibrium [280-282], conformational changes [283], dissociation reactions [199, 200, 227], stability [284] - have been treated by these techniques. Some of these... 

---