Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · cond-mat/0510146

Nematic-Isotropic Interfaces Under Shear: A Molecular Dynamics Simulation

Guido Germano·Friederike Schmid
View original source ↗Read source document ↗Export metadata ↓

Abstract

We present a large-scale molecular dynamics study of nematic-paranematic interfaces under shear. We use a model of soft repulsive ellipsoidal particles with well-known equilibrium properties, and consider interfaces which are oriented normal to the direction of the shear gradient (common stress case). The director at the interface is oriented parallel to the interface (planar). A fixed average shear rate is imposed with Lees-Edwards boundary conditions, and the heat is dissipated with a profile-unbiased thermostat. First we study the properties of the interface at one particular shear rate in detail. The local interfacial profiles and the capillary wave fluctuations of the interfaces are calculated and compared with those of the corresponding equilibrium interface. Under shear, the interfacial width broadens and the capillary wave amplitudes at large wavelengths increase. The strain is distributed inhomogeneously in the system (shear banding), the local shear rate in the nematic region being distinctly higher than in the paranematic region. Surprisingly, we also observe (symmetry breaking) flow in the {\em vorticity} direction, with opposite direction in the nematic and the paranematic state. Finally, we investigate the stability of the interface for other shear rates and construct a nonequilibrium phase diagram.

Explore related subjects

cond-mat.softcond-mat.mtrl-sci

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Guido Germano, Friederike Schmid. 2005-10-06. Nematic-Isotropic Interfaces Under Shear: A Molecular Dynamics Simulation. https://doi.org/10.1063/1.2131065

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Reciprocal theorem for ion-releasing colloidal particles

We describe a generalization of the reciprocal theorem for particles suspended in electrolyte solutions and subjected to an electric field that could be either applied or emerged spontaneously. Attention is focused on catalytic colloids that release ions. The power of the generalization is to capture the effect of formation of a secondary cloud around a catalytic particle, which is equivalent to accounting for an excess charge $Q$ of a system. Our results show that the propulsion speed of catalytic particles has an extra contribution proportional to $Q$ and an external field $E_{\infty}$. The derived equation for $Q$ reveals that its sign is defined by the difference in the ion diffusivity and the magnitude is controlled by the average flux of ions from the surface. We demonstrate the application of the generalized theorem to electro- and diffusiophoresis of homogeneously releasing ions passive particles, as well as to a self-propulsion of inhomogeneous active particles (microswimmers). It is shown that whilst in some situations the extra term in the reciprocal theorem vanishes or has a little effect on the particle mobility, in many others it may dramatically change its magnitude, and even sign. In addition, the relevance of our results for microswimmer interactions is discussed briefly.

cond-mat.soft↗
arXiv2026

Multigeometric Breathing Mode Framework for viruses

The estimation of the breathing mode frequency for viral capsids remains a persistent challenge across literature which spawned various frameworks and methodologies. However, discrepancies were observed between the experimental Low Frequency Raman Scattering (LFRS) and calculated pre-existing values. To solve this discrepancy, we propose a framework which is developed to determine the breathing-mode frequency by modelling the virus as a macroscopic coupled harmonic oscillator. By integrating mass-loading directly into the classical elastodynamic equations, this model yields an analytical expression that couples the system's total inertia with its specific geometry. Moreover, the viruses are segregated according to their geometries into three coordinates to acquire their respective geometric eigen values. Here we illustrate how the proposed Multigeometric Breathing mode Framework for Virus (MBFV) outperforms prior models by yielding closer values than the pre-existing frameworks upon validating against LFRS.

cond-mat.soft↗
arXiv2026

Insight into ordering at nematic twist-bend interfaces

Twist-bend nematics formed by achiral particles support heliconical domains of opposite handedness. Using Monte Carlo and molecular dynamics simulations of repulsive bent particles, we study the interface between two such domains. Rather than a gradually untwisting texture, we find a density-modulated splay-bend-twist structure. The density modulation is along the helix axis with a period of approximately half the bulk pitch, while the twist is locally enhanced in magnitude, alternates in sign, and vanishes only on an undulating surface. An explicit director interpolation shows how gradients along the helix axis and across the interface combine to produce an undulating zero-twist surface.

cond-mat.soft↗