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Bend-shear-mode instabilities of nematic liquid crystals in ac fields

1974; American Institute of Physics; Volume: 9; Issue: 6 Linguagem: Inglês

10.1103/physreva.9.2698

0556-2791

Papiya Sengupta, A. Saupe,

Surfactants and Colloidal Systems

Hydrodynamic instabilities of nematic liquid crystals with a negative dielectric anisotropy in ac electric fields are theoretically studied. The instabilities considered are due to the development of bend modes coupled with flow fields of equal periodicity (Carr, Helfrich). A simple numerical procedure is developed which allows a convenient and exact calculation of threshold curves and instability regions which depend essentially only on two parameters, the reduced cutoff frequency and the reduced decay time of the bend-shear mode. Results of numerical calculations are presented in stability charts using reduced field and frequency coordinates. Characteristic features of threshold curves are discussed and a general survey is given on the position and the extent of instability regions.