Helicoidal dynamics of biaxial curved rods in twist-bend nematic phases unveiled by unsupervised machine learning techniques

Chiappini, Massimiliano; Patti, Alessandro; Dijkstra, Marjolein

doi:10.1103/physreve.102.040601

Cited by 22 publications

(18 citation statements)

References 53 publications

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“…In DMC simulations, to realistically mimic the Brownian motion of colloidal particles, unphysical moves, such as swaps or cluster moves, are not performed. An insightful description of the DMC method applied in this work is available elsewhere [24][25][26][27][28][29]. Here we only provide a brief overview of the main features of the method and refer the interested reader to these works for details.…”

Section: Model and Simulationsmentioning

confidence: 99%

“…These limitations can be bypassed by the Dynamic Monte Carlo (DMC) method, which is able to capture the Brownian dynamics of colloids without employing stochastic or deterministic equations of motion. Based on the standard Metropolis algorithm [21], DMC can quantitatively and qualitatively reproduce BD simulation results in the limit of small displacements [22][23][24][25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

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Long-time relaxation dynamics in nematic and smectic liquid crystals of soft-repulsive colloidal rods

Cywiak,

Gil-Villegas,

Patti

2021

Preprint

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Understanding the relaxation dynamics of colloidal suspensions is crucial to identify the elements that influence the mobility of their constituents, assess their macroscopic response across the relevant time and length scales, and thus disclose the fundamentals underpinning their exploitation in formulation engineering. In this work, we specifically assess the impact of long-ranged ordering on the relaxation dynamics of suspensions of soft-repulsive rod-like particles, which are able to selforganise into nematic and smectic liquid-crystalline phases. By performing Dynamic Monte Carlo simulations, we analyse the effect of translational and orientational order on the diffusion of the rods along the relevant directions imposed by the morphology of the background phases. To provide a clear picture of the resulting dynamics, we assess their dependence on temperature, which can dramatically determine the response time of the system relaxation and the self-diffusion coefficients of the rods. The computation of the van Hove correlation functions allows us to identify the existence of rods that diffuse significantly faster than the average and whose concentration can be accurately adjusted by a suitable choice of temperature.

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Section: Model and Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Long-time relaxation dynamics in nematic and smectic liquid crystals of soft-repulsive colloidal rods

Cywiak,

Gil-Villegas,

Patti

2021

Preprint

Self Cite

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“…To study the dynamics, we performed DMC simulations in the canonical ensemble. The DMC method has been discussed elsewhere [55][56][57][58][59] . Here we only present its essential features and refer the interested reader to these works for details.…”

Section: Productionmentioning

confidence: 99%

“…Regardless the DMC time step employed in Eqs. ( 2) and (3), the actual time scale of Brownian dynamics, t BD , must be recovered [55][56][57][58][59] . The rescaling to the BD timescale is crucial to ensure a consistent comparison between the dynamics of different families of particles (e.g.…”

Section: Productionmentioning

confidence: 99%

Dynamics of Colloidal Cubes and Cuboids in Cylindrical Nanopores

Patti,

Cuetos

2021

Preprint

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Understanding how colloidal suspensions behave in confined environments has a striking relevance in practical applications. Despite the fact that the behaviour of colloids in the bulk is key to identify the main elements affecting their equilibrium and dynamics, it is only by studying their response under confinement that one can ponder the use of colloids in formulation technology. In particular, confining fluids of anisotropic particles in nanopores provides the opportunity to control their phase behaviour and stabilise a spectrum of morphologies that cannot form in the bulk. By properly selecting pore geometry, particle architecture and system packing, it is possible to tune thermodynamic, structural and dynamical properties for ad hoc applications. In the present contribution, we report Grand Canonical and Dynamic Monte Carlo simulations of suspensions of colloidal cubes and cuboids constrained into cylindrical nanopores of different size. We first study their phase behaviour, calculate the chemical potential vs density equation of state and characterise the effect of the pore walls on particle anchoring and layering. In particular, at large enough concentrations, we observe the formation of concentric nematic-like coronas of oblate or prolate particles surrounding an isotropic core, whose features resemble those typically detected in the bulk. We then analyse the main characteristics of their dynamics and discover that these are dramatically determined by the ability of particles to diffuse in the longitudinal and radial direction of the nanopore.

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“…With this in mind, over the last years, our group has developed a stochastic method that can qualitatively and quantitatively mimic the Brownian motion of colloids as obtained by BD simulations [33][34][35][36] . This method, re-ferred to as Dynamic Monte Carlo (DMC), has become an established simulation technique not only for the study of the dynamics of biaxial particles, such as cuboids and curved rods 37,38 , but also for the dynamics of uniaxial particles, like rods, for which soft potentials are indeed available 39,40 .…”

Section: Introductionmentioning

confidence: 99%

Dynamics of Uniaxial-to-Biaxial Nematics Switching in Suspensions of Hard Cuboids

Rafael,

Tonti,

Corbett

et al. 2021

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Field-induced reorientation of colloidal particles is especially relevant to manipulate the optical properties of a nanomaterial for target applications. We have recently shown that surprisingly feeble external stimuli are able to transform uniaxial nematic liquid crystals (LCs) of cuboidal particles into biaxial nematic LCs. In the light of these results, here we apply an external field that forces the reorientation of colloidal cuboids in nematic LCs and sparks a uniaxial-to-biaxial texture switching. By Dynamic Monte Carlo simulation, we investigate the unsteady-state reorientation dynamics at the particle scale when the field is applied (uniaxial-to-biaxial switching) and then removed (biaxial-to-uniaxial switching). We detect a strong correlation between the response time, being the time taken for the system to reorient, and particle anisotropy, which spans from rod-like to plate-like geometries. Interestingly, self-dual shaped cuboids, theoretically considered as the most suitable to promote phase biaxiality for being exactly in between prolate and oblate particles, exhibit surprisingly slow response times, especially if compared to prolate cuboids.

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Helicoidal dynamics of biaxial curved rods in twist-bend nematic phases unveiled by unsupervised machine learning techniques

Abstract: Helicoidal dynamics of biaxial curved rods in twist-bend nematic phases unveiled by unsupervised machine learning techniques. Physical Review E, 102(4).

Cited by 22 publications

References 53 publications

Long-time relaxation dynamics in nematic and smectic liquid crystals of soft-repulsive colloidal rods

Long-time relaxation dynamics in nematic and smectic liquid crystals of soft-repulsive colloidal rods

Dynamics of Colloidal Cubes and Cuboids in Cylindrical Nanopores

Dynamics of Uniaxial-to-Biaxial Nematics Switching in Suspensions of Hard Cuboids

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