Kinetic Pathways for the Isotropic-Nematic Phase Transition in a System of Colloidal Hard Rods: A Simulation Study

Abstract

We study the kinetic pathways for the isotropic-to-nematic transition in a fluid of colloidal hard rods. In order to follow the formation of the nematic phase, we develop a new cluster criterion that distinguishes nematic clusters from the isotropic phase. Applying this criterion in Monte Carlo simulations, we find spinodal decomposition as well as nucleation and growth depending on the supersaturation. We determine the height of the nucleation barrier and we study the shape and structure of the cluster. More specifically, we find ellipsoidal nematic clusters with an aspect ratio of about 1.7 and a homogeneous nematic director field. Our results are consistent with theoretical predictions on the shape and director field of nematic tactoids. Classical nucleation theory gives reasonable predictions for the height of the nucleation barrier and the critical nucleus size.

Nonmonotonic size dependence of the critical concentration in 2D percolation of straight rigid rods under equilibrium conditions

“…On the other hand, numerous experimental and numerical studies have been recently devoted to the analysis of equilibrium properties in systems of non-spherical particles [18,19,20,21,22,23,24,25,26]. Of special interest are those studies dealing with lattice versions of the present problem, where the situation is much less clear than in the continuum case.…”

Magnetic field effects on tactoids of plate-like colloids

“…8 Very recently, tactoids in systems of rods have also been investigated by means of computer simulation. [9][10][11][12] These nematic droplets have an unusual, elongated (spindle-like) shape and are characterized by a bipolar director field as is evidenced by polarization microscopy, a consequence of the a) Electronic mail: a.a.verhoeff@uu.nl. planar anchoring of the nematic director field to the isotropicnematic interface observed in this kind of system.…”

“…8,13,15,16 The latter was consistently found to be significantly larger than predicted by theory and computer simulations. 10,[17][18][19][20][21] This has been attributed to the effects of curvature, but this is by no means certain. 22 Additional information on the material properties of tactoids can be obtained by means of an externally applied electrical or magnetic field because these couple to their shape and director field.…”

Isotropic–nematic phase transition in the Lebwohl–Lasher model from density of states simulations

“…To do this, we adapt a novel approach for the identification of ordered domains originally proposed in the context of colloidal hard rods by Cuetos and Dijkstra. 5 The paper is organized as follows. In Sec.…”

“…Previous computational studies of LC models have examined both mechanisms. 1,[3][4][5][6][7][8][9][10][11][12][13][14][15] Here, we examine the nature of the IN phase transition using the Lebwohl-Lasher (LL) model, a minimal lattice LC model whose simplicity has attracted significant research. 4,7,13,14,[16][17][18][19][20][21][22] To the best of our knowledge, the transition mechanism for the LL model has not been studied previously.…”