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An atomistic description of the nematic and smectic phases of 4-n-octyl-4′ cyanobiphenyl (8CB)
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10.1063/1.4804270
/content/aip/journal/jcp/138/20/10.1063/1.4804270
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/20/10.1063/1.4804270

Figures

Image of FIG. 1.
FIG. 1.

Comparison between experimental and simulated density as a function of temperature. is the percent deviation of the simulated density from the experimental value. Vertical dashed lines represent the experimental transition temperatures and .

Image of FIG. 2.
FIG. 2.

Orientational order parameters ⟨ ⟩ and ⟨ ⟩ of the simulated sample compared to different sets of experimental data as a function of temperature. Data from refractive index measurements in Refs. (a)–(c) and from polarized Raman spectroscopy measurements in Refs. (d)–(f).

Image of FIG. 3.
FIG. 3.

Histograms of the instantaneous values of nematic order parameter () for all the configurations obtained in each temperature production run.

Image of FIG. 4.
FIG. 4.

Variation of the 8CB dipole orientational correlation functions (), () and of the radial distribution of centers of charge, () for samples at 304, 311, and 316 K (representing the smectic, nematic, and isotropic phases, respectively).

Image of FIG. 5.
FIG. 5.

The typical positional and orientational arrangement of neighbouring molecules belonging to two different sublayers in the SmA phase. is the layer spacing and = − 2λ is the interdigitation. The center of charge, which turns out to be pretty conformation independent, is located on the red colored carbon atom.

Image of FIG. 6.
FIG. 6.

The density autocorrelation ( ) for systems , , , and .

Image of FIG. 7.
FIG. 7.

Density correlation ( ) along the z axis for samples at 304, 311, and 316 K (representing the smectic, nematic, and isotropic phases, respectively).

Image of FIG. 8.
FIG. 8.

Comparison of and two particle autocorrelation function ( ) with the one of the whole sample ( ) for system . Here ( ) is a best fit function to the actual one which has been shifted of λ so that it yields the total ( ) when combined with ( ) (see Eq. (15) ).

Image of FIG. 9.
FIG. 9.

Layer interdigitation in system (replicated twice along x, y, and z axes). Red and blue colors represent parallel (“up”) and antiparallel (“down”) molecules.

Image of FIG. 10.
FIG. 10.

Arrhenius plot of simulation-rescaled and experimental diffusion coefficients. Green filled symbols represent experimental values, blue empty symbols represent rescaled values from simulations, orange empty symbols represent values calculated with CM model. Dashed lines correspond to experimental transition temperatures.

Image of FIG. 11.
FIG. 11.

τ(′) as a function of the trial layer spacing ′ for simulated system (color filled regions) and for method I with τ = 0.11, = 31.6 Å, = 110 Å, and = 14 Å, with (blue lines, Eq. (A10) ) and without (green lines, Eq. (A1) ) removal of the spurious factor.

Tables

Generic image for table
Table I.

Simulated values with respect to the temperature of: positional order parameter and layer spacing from method I: (τ), ; positional order parameters and layer spacing from method II: (τ), and ; shift between and sublayers λ; sublayer interdigitation ɛ; experimental layer spacing .

Generic image for table
Table II.

Comparison of the positional order parameter τ, the layer spacing and second rank orientational order parameter ⟨ ⟩ from the most recent computational and experimental work available in literature. All atom, core, and atoms refer to computations run on all atoms, on the phenyl core, and on the nitrogen atom only, respectively.

Generic image for table
Table III.

Mixed order parameters compared to the products of the average order parameters ⟨ ⟩τ. The positional term τ and the layer spacing were computed according to procedure described in Appendix A (method I).

Generic image for table
Table IV.

Simulated values with respect to the temperature of: mass density ρ – nematic order parameter ⟨ ⟩ – average value of the length to breadth molecular aspect ratio /, calculated from the dimensions of the minimal rectangular box containing the molecule rotated in its inertial frame – diffusion coefficients in 10 m/s: isotropic coefficient , rescaled isotropic coefficient , parallel coefficient from rescaled isotropic through CM model , perpendicular coefficient from rescaled isotropic through CM model .

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/content/aip/journal/jcp/138/20/10.1063/1.4804270
2013-05-22
2014-04-16
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: An atomistic description of the nematic and smectic phases of 4-n-octyl-4′ cyanobiphenyl (8CB)
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/20/10.1063/1.4804270
10.1063/1.4804270
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