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Imperfections in Focal Conic Domains: the Role of Dislocations

By Maurice Kléman, Claire Meyer and Yuri A. Nastishin

Abstract

à paraître dans Philosophical magazineIt is usual to think of Focal Conic Domains (FCD) as perfect geometric constructions in which the layers are folded into Dupin cyclides, about an ellipse and a hyperbola that are conjugate. This ideal picture is often far from reality. We have investigated in detail the FCDs in several materials that have a transition from a smectic A (SmA) to a nematic phase (N). The ellipse and the hyperbola are seldom perfect, and the FCD textures also suffer large transformations (in shape or/and in nature) when approaching the transition to the nematic phase, or appear imperfect on cooling from the nematic phase. We interpret these imperfections as due to the interaction of FCDs with dislocations. We analyze theoretically the general principles subtending the interaction mechanisms between FCDs and finite Burgers vector dislocations, namely the formation of \textit{kinks} on disclinations, to which dislocations are attached, and we present models relating to some experimental results. Whereas the principles of the interactions are very general, their realizations can differ widely in function of the boundary conditions

Topics: liquid crystals, Focal Conic Domains, screw dislocations, kinks, pacs: 61.30Jf, 61.72Lk, [PHYS.COND.CM-SCM] Physics [physics]/Condensed Matter [cond-mat]/Soft Condensed Matter [cond-mat.soft]
Publisher: HAL CCSD
Year: 2006
OAI identifier: oai:HAL:hal-00022038v1
Provided by: Hal-Diderot
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