Dynamic Monte Carlo simulations of anisotropic colloids

It is well known that understanding the transport properties of liquid crystals (LCs) is crucial to optimise their performance in a number of technological applications. In this work, we analyse the effect of shape anisotropy on the diffusion of rod-like and disk-like particles by Brownian dynamics simulations. To this end, we compare the dynamics of prolate and oblate nematic LCs incorporating particles with the same infinite-dilution translational or rotational diffusion coefficients. Under these conditions, which are benchmarked against the standard case of identical aspect ratios, we observe that prolate particles display faster dynamics than oblate particles at short and long timescales. Nevertheless, when compared at identical infinite-dilution translational diffusion coefficients, oblate particles are faster than their prolate counterparts at short-to-intermediate timescales, which extend over almost three time decades. Both oblate and prolate particles exhibit an anisotropic diffusion with respect to the orientation of the nematic director. More specifically, prolate particles show a fast diffusion in the direction parallel to the nematic director, while their diffusion in the direction perpendicular to it is slower. By contrast, the diffusion of oblate particles is faster in the plane perpendicular to the nematic director. Finally, in the light of our recent study on the longtime Gaussian and Fickian diffusion in nematic LCs, we map the decay of the autocorrelation functions and their fluctuations over the timescales of our simulations to ponder the existence of mobile clusters of particles and the occurrence of collective motion.

Section: Resultssupporting

confidence: 87%

Section: Discussionsupporting

confidence: 83%

See 1 more Smart Citation

Brownian dynamics simulations of oblate and prolate colloidal particles in nematic liquid crystals

Morillo

Patti

Cuetos

2019

“…We further investigated the dynamics of the orientationally disordered structures with vanishing S = 0 by means of dynamic Monte-Carlo (DMC) that we have developed for anisotropic colloids [35]. In this case, very small values of displacements were used and we performed 0.1 − 2 × 10 7 MC cycles to obtain the dynamical quantities.…”

Section: Simulation Methods and Detailsmentioning

confidence: 99%

Interplay of anisotropy in shape and interactions in charged platelet suspensions

Jabbari-Farouji

Weis

Levitz

et al. 2014

Self Cite

Motivated by the intriguing phase behavior of charged colloidal platelets, we investigate the structure and dynamics of charged repulsive disks by means of Monte-Carlo simulations. The electrostatic interactions are taken into account through an effective two-body potential, obtained within the nonlinear Poisson-Boltzmann formalism, which has the form of anisotropic screened Coulomb potential. Recently, we showed that the original intrinsic anisotropy of the electrostatic potential in competition with excluded volume effects leads to a rich phase behavior that not only includes various liquid-crsytalline phases but also predicts the existence of novel structures composed of alternating nematic-antinematic sheets. Here, we examine the structural and dynamical signatures of each of the observed structures for both translational and rotational degrees of freedom. Finally, we discuss the influence of effective charge value and our results in relation to experimental findings on charged platelet suspensions.

“…It was found that Monte Carlo simulations in which physically relevant moves (small particle displacements) are used, are a correct and efficient way to investigate the dynamics in colloidal systems. [43][44][45] Molecular dynamics simulations are less appropriate to describe the dynamics in suspensions of colloidal particles, as they employ Newtonian dynamics rather than the Brownian dynamics which is operative in colloidal systems. We expect only limited fractionation, to the extent introduced by the selected initial configuration and allowed for by the diffusion of the particles on simulation timescales.…”

Section: Introductionmentioning

confidence: 99%

Effect of size polydispersity on the crystal-fluid and crystal-glass transition in hard-core repulsive Yukawa systems

Linden¹,

Blaaderen²,

Dijkstra³

2013

We investigated the effect of size polydispersity on the crystal-fluid transition in hard-core repulsive Yukawa systems by means of Monte Carlo simulations for several state points in the Yukawa parameter space. Size polydispersity was introduced in the system only with respect to the hard particle cores; particles with different diameters had the same surface potential ψ 0 , but the charge per particle was not varied with packing fraction or distance. We observed a shift to higher packing fraction of the crystal-fluid transition of bulk crystals with a fixed log-normal size distribution upon increasing the polydispersity, which was more pronounced for weakly charged particles (ψ 0 ≈ 23 mV) compared to more highly charged particles (ψ 0 ≈ 46 mV), and also more pronounced for larger Debye screening length. At high polydispersities (≥0.13) parts of the more highly charged systems that were initially crystalline became amorphous. The amorphous parts had a higher polydispersity than the crystalline parts, indicating the presence of a terminal polydispersity beyond which the homogeneous crystal phase was no longer stable.