Viscosity of a room temperature ionic liquid: predictions from nonequilibrium and equilibrium molecular dynamics
Oleg Borodin1, Grant D Smith, Hojin Kim
1Department of Materials Science & Engineering, 122 South Central Campus Drive, Room 304, University of Utah, Salt Lake City, Utah 84112-0560, USA. Oleg.Borodin@utah.edu
Abstract:
Nonequilibrium molecular dynamics (NEMD) simulations have been performed on 1-methyl-3-ethyl-imidazolium bis(trifluoromethane)sulfonimide [emim][Ntf(2)] using Lees-Edwards boundary conditions. A range of inverse shear rates corresponding to a fraction of the rotational relaxation time for the slowest relaxing molecular axis of anion and cation to 20 rotational relaxation times (1/20 tau(rot) < gamma < 5/tau(rot)) has been investigated. An extrapolation of the shear-rate-dependent viscosity obtained from these simulations to zero shear rate using the empirical three-parameter Carreau equation yielded excellent agreement with the viscosity obtained from equilibrium MD simulations. Based upon the Carreau equation fit to the simulation data, shear-thinning behavior was observed in [emim][Ntf(2)] for all shear rates investigated, implying that Newtonian behavior is observed in [emim][Ntf(2)] only for shear rates significantly lower than the inverse rotational relaxation time. A close resemblance between the apparent time-dependent viscosity extracted from equilibrium MD simulations and the shear-rate-dependent viscosity extracted from NEMD simulations has been found and discussed. MD simulations accurately predicted [emim][Ntf(2)] density, self-diffusion coefficients, heat of vaporization, and lattice parameters for the crystalline phase.
More Related Videos
Related Concept Videos
Surface Tension, Capillary Action, and Viscosity
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
Viscosity of Fluid
Viscosity
Viscosity
The SI unit of viscosity is...
Distillation: Vapor–Liquid Equilibria
Distribution of Molecular Speeds


