Travelling Waves in Electroconvection of the Nematic Phase 5: A Test of the Weak Electrolyte ModelReport as inadecuate




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Abstract : We investigated travelling waves appearing as the primary pattern–forming instability in the nematic Phase 5 Merck in the planar geometry in order to test the recently developed weak electrolyte model of ac–driven electroconvection 1. Travelling waves are observed over the full conductive range of applied frequencies for three cells of different layer thickness d. We also measured the elastic constants, the electric conductivity, and the dielectric constant. The other parameters of Phase 5 are known, apart from the relatively unimportant viscosity α1 and the two parameters of the weak electrolyte model that are proportional to the geometric mean of the mobilities, and the recombination rate, respectively. Assuming a sufficiently small recombination rate, the predicted dependence of the frequency of the travelling waves at onset Hopf frequency on d and on the applied frequency agreed quantitatively with the experiments, essentially without fit parameters. The absolute value of the Hopf frequency implies that the geometric mean of the mobilities amounts to $1.1 \times 10^{-10}~{ m m}^2$-Vs.





Author: Martin Treiber Nándor Éber Ágnes Buka Lorenz Kramer

Source: https://hal.archives-ouvertes.fr/



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