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Isotropic-nematic spinodals of rigid long thin rodlike colloids by event-driven Brownian dynamics simulations
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10.1063/1.2180251
/content/aip/journal/jcp/124/13/10.1063/1.2180251
http://aip.metastore.ingenta.com/content/aip/journal/jcp/124/13/10.1063/1.2180251
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

A cartoon of the trajectories of three interacting rods during one time step . On the left-hand side, , , and mark the start positions of the rods. On the right-hand side, , , and denote the prospective positions of the rods at the end of the step for the given initial set of random forces and torques. At the collision moments and new random forces and torques are drawn for the two colliding particles. The resulting modified final positions are indicated by (double) primed indices. The solid lines denote the traversed trajectories; dotted lines are extrapolations.

Image of FIG. 2.
FIG. 2.

The rotational self-diffusion coefficients of rigid rods with aspect ratios of and 68 as functions of the scaled volume fraction . The open symbols denote results calculated with the new event-driven algorithm for hard rods, while the solid symbols are obtained by our previous algorithm in which the interaction potential between rods was proportional to their overlap volume.

Image of FIG. 3.
FIG. 3.

The rotational self-diffusion coefficients of rigid rods with various aspect ratios as functions of the scaled volume fraction.

Image of FIG. 4.
FIG. 4.

The rotational self-diffusion coefficients of rigid rods with various aspect ratios as functions of the scaled volume fraction on log-log scale. Here is the number density. The solid line is a linear fit based on the results for .

Image of FIG. 5.
FIG. 5.

The simulated self (circles) and collective (squares) rotational diffusion coefficients as functions of the scaled volume fraction for solutions of rods with .

Image of FIG. 6.
FIG. 6.

The scalar order parameter vs the scaled volume fraction for solutions of rods with an aspect ratio of . The closed circles and open squares denote stationary order parameters obtained when starting the simulations with perfectly aligned and isotropic boxes, respectively. The collective rotational diffusion coefficients are plotted as triangles. The closed triangles are calculated from the decay of an initially aligned state; the open triangles are obtained by autocorrelating thermal fluctuations, see Eq. (28). The dashed line is a fit with Eq. (29), reaching zero at the isotropic-nematic spinodal indicated by an arrow.

Image of FIG. 7.
FIG. 7.

The scalar order parameters and collective rotational diffusion coefficients as functions of the scaled volume fraction for aspect ratios of 10 (a), 15 (b), 30 (c), and 60 (d). The arrows and numbers refer to the INS spinodals obtained by using Eq. (29). The values of in (a)–(d) are multiplied by 5, 8, 10, and 20, respectively.

Image of FIG. 8.
FIG. 8.

The INS (solid squares) and NIS (solid circles) spinodals as functions of . The open squares and circles are the binodals calculated in Ref. 19. The use of , rather than the shape anisotropy , facilitates the comparison with theoretical predictions. The theoretical binodals (open triangles) and spinodals (solid triangles) at infinite aspect ratio are plotted on the axis for ; these points were not included when fitting the lines.

Image of FIG. 9.
FIG. 9.

(a) The theoretical scalar order parameter as a function of the scaled volume fraction at various shear rates for . At low shear rates, the flow induces a small paranematic alignment in the isotropic phase and increases the alignment of the nematic phase. The end points of these lines are the INS and NIS spinodals, which are plotted in (b) as a function of the Peclet number . At the critical shear rate, corresponding to , the spinodals coalesce and end; hence the two phases merge into a single phase.

Image of FIG. 10.
FIG. 10.

The simulated scalar order parameters as functions of the scaled volume fraction at various shear rates for (a) and (b) .

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/content/aip/journal/jcp/124/13/10.1063/1.2180251
2006-04-06
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Isotropic-nematic spinodals of rigid long thin rodlike colloids by event-driven Brownian dynamics simulations
http://aip.metastore.ingenta.com/content/aip/journal/jcp/124/13/10.1063/1.2180251
10.1063/1.2180251
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