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Molecular dynamics simulations of n-hexane at 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide interface
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10.1063/1.4811673
/content/aip/journal/jcp/139/1/10.1063/1.4811673
http://aip.metastore.ingenta.com/content/aip/journal/jcp/139/1/10.1063/1.4811673

Figures

Image of FIG. 1.
FIG. 1.

Chemical structures of (a) bmim, (b) TfN, and (c) n-hexane along with atom types.

Image of FIG. 2.
FIG. 2.

The surface tension, γ, for the [bmim][TfN]/n-hexane systems at a temperature of 300 K as a function of the n-hexane surface density, ρ. Open circles represent our simulation results while the filled circle corresponds the experimental result for the neat interface. The simulation result for the neat interface is taken from our previous work. Dotted lines serve as a guide to the eye.

Image of FIG. 3.
FIG. 3.

Number (left column) and charge (right column) density profiles of cations, anions, ion pairs (total) and n-hexane for the [bmim][TfN]/n-hexane systems, evaluated for the overall system and for the interfacial, sub-interfacial, and central layers at a temperature of 300 K; (a) the neat interface (taken from our previous work ), (b) the interface with the n-hexane surface density ρ = 0.743 μmol/m, and (c) the interface with ρ = 2.228 μmol/m. The scale on the axis shows distances where the total density is half the bulk density.

Image of FIG. 4.
FIG. 4.

Intrinsic number density profiles for the individual atoms that belong to the ions and n-hexane in the interfacial layer of the [bmim][TfN]/n-hexane systems at a temperature of 300 K. (a) The neat interface, (b) the interface with the n-hexane surface density ρ = 0.743 μmol/m, and (c) the interface with ρ = 2.228 μmol/m. The scale on the axis shows distances from the true positions of the interface.

Image of FIG. 5.
FIG. 5.

(a) Diagram showing the coordinate axes used for the orientation analysis of bmim. (b) Diagram displaying the three main orientations of the bmim.

Image of FIG. 6.
FIG. 6.

Orientation of bmim and TfN in the interfacial layer of the [bmim][TfN]/n-hexane systems at a temperature of 300 K (red = high probability, blue = low probability). The first column: probability distribution (cos θ, Φ) for the imidazolium ring of bmim; θ and Φ are the angles depicted in Fig. 5(a) ; the second column: two-dimensional plot (cos θ, ) for the alkyl chain of bmim; θ is the tilt angle of the vector N-C with respect to the interface normal ; the third column: probability distribution (cos θ, cos Φ) for TfN; θ is the tilt angle of the vectors S-C with respect to and Φ is the tilt angle of the vector S-S with respect to ; the fourth column: probability distribution (cos θ, cos Φ) for TfN; θ is the tilt angle of the vectors S-O with respect to and Φ is the tilt angle of the vector S-S with respect to . (a) the neat interface, (b) the interface with the n-hexane surface density ρ = 0.743 μmol/m, and (c) the interface with ρ = 2.228 μmol/m.

Image of FIG. 7.
FIG. 7.

Two-dimensional plot (cos θ, ) of n-hexane molecules in the adsorbed layer onto the [bmim][TfN] interface at a temperature of 300 K; θ is the tilt angle of the vector C-C with respect to the interface normal . (a) The interface with the n-hexane surface density ρ = 0.743 μmol/m, (b) the interface with ρ = 0.1.418 μmol/m, and (c) the interface with ρ = 2.228 μmol/m.

Image of FIG. 8.
FIG. 8.

Survival probability, (), for the cation, anion and n-hexane in the interfacial and sub-interfacial layers of the [bmim][TfN]/n-hexane systems at a temperature of 300 K; is time. (a) the neat interface (taken from our previous work ), (b) the interface with the n-hexane surface density ρ = 0.743 μmol/m, (c) the interface with ρ = 0.1.418 μmol/m, and (d) the interface with ρ = 2.228 μmol/m.

Tables

Generic image for table
Table I.

The surface density of the molecules ρ, cation, anion, and n-hexane mole fractions, , , and = 1 − , respectively, and the amplitude of the surface roughness, , and frequency-like parameters of the surface roughness, ξ and , in the interfacial and sub-interfacial layers of the [bmim][TfN]/n-hexane systems at a temperature of 300 K; ρ is the n-hexane surface density. Results for the neat [bmim][TfN] interface is taken from our previous work.

Generic image for table
Table II.

The stretched exponent β, characteristic residence time τ, and average residence time τ of the stretched exponential decay (4) for bmim, TfN, and n-hexane in the interfacial and sub-interfacial layers of the [bmim][TfN]/n-hexane systems at a temperature of 300 K; ρ is the n-hexane surface density. Results for the neat [bmim][TfN] interface is taken from our previous work.

Generic image for table
Table III.

The normal and lateral self-diffusion coefficients, and , respectively, of bmim, TfN, and n-hexane in the interfacial, sub-interfacial, and central layers of the [bmim][TfN]/n-hexane systems at a temperature of 300 K; ρ is the n-hexane surface density. Results for the neat [bmim][TfN] interface is taken from our previous work. Also listed are the values of the self-diffusion coefficients in the bulk [bmim][TfN] predicted from the MD simulations of Logotheti and obtained experimentally by Tokuda

Generic image for table
Table IV.

The stretched exponent β, characteristic re-orientation time τ, and average re-orientation time τ of the stretched exponential decay, () = exp [−(/τ)], for the vectors C-C and C-H on bmim, vectors S-S and S-C on TfN, and vector C-C on n-hexane molecule in the interfacial, sub-interfacial, and central layers of the [bmim][TfN]/n-hexane systems at a temperature of 300 K; ρ is the n-hexane surface density. Results for the neat [bmim][TfN] interface is taken from our previous work.

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/content/aip/journal/jcp/139/1/10.1063/1.4811673
2013-07-03
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Molecular dynamics simulations of n-hexane at 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide interface
http://aip.metastore.ingenta.com/content/aip/journal/jcp/139/1/10.1063/1.4811673
10.1063/1.4811673
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