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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 18:24 |
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Conference: Bucharest University Faculty of Physics 2009 Meeting
Section: Polymer Physics
Title:
Electrohydrodynamic Instabilities in SmC* Liquid Crystal Films
Authors:
Lucian Georgescu, Cristina Miron, Narcisa Bândă
Affiliation:
University of Bucharest, Faculty of Physics, POB MG – 11, Romania
E-mail
cmiron_2001@yahoo.com
Keywords:
electrohydrodynamic instabilities, SmC* films, Freedericksz transition, convective phenomena.
Abstract:
Describing the SmC* film by a two – dimensional theory we find for low and high frequencies of the applied electric AC field, respectively, a conductive and a dielectric instability regime, similar to the case of electroconvective in a nematic liquid crystals. Compared to nematic liquid crystals the SmC* phase shows in addition a macroscopic electric polarization within the smectic phases. Because of the polarization in the SmC* phase an additional, new subharmonic regime appears at intermediate frequencies, where all the hydrodynamic and electric variables are moving with half the frequency of the applied AC voltage at the onset of convection. For DC voltage the generalized Freedericksz transition is presented and discussed as for as it restricts the observation of pattern forming convective instabilities. Both types of instabilities are investigated for DC voltages to get a fundamental insight into the mechanism involved as well as for AC voltages.
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