TY - JOUR

T1 - Director dynamics near the nematic-smectic-A phase transition

AU - Ul'yanov, S. V.

N1 - Copyright: Copyright 2018 Elsevier B.V., All rights reserved.

PY - 1998/12

Y1 - 1998/12

N2 - The Landau-de Gennes model for the free energy of a nematic liquid crystal near the phase transition to the smectic A-phase is used to determine the frequency dependence of the fluctuation corrections to the Frank elastic constants. It is shown that the interaction of the fluctuations of the smectic order parameter and the director results in corrections to all the Frank elastic constants. In the low-frequency limit (ω→0), the corrections to the Frank elastic constants K22 and K33 are the largest, and decrease to zero in the infinite-frequency limit. The correction to K11 is negative, and vanishes in both limits. The absolute value of the correction to K11 is the largest at frequencies in the megahertz range. It is shown that in oriented ncmatics the interaction of the smectic fluctuations and the director limits deviations of the director from the direction of preferred orientation, as a result of which relaxation of both inhomogeneous and homogeneous distortions of the director field can be observed. It is also shown that this gives rise to a frequency interval in the megahertz range in which shear waves begin to propagate in the nematic. The propagation speed of these waves is roughly a hundred times smaller than that of sound and strongly depends on the direction of propagation.

AB - The Landau-de Gennes model for the free energy of a nematic liquid crystal near the phase transition to the smectic A-phase is used to determine the frequency dependence of the fluctuation corrections to the Frank elastic constants. It is shown that the interaction of the fluctuations of the smectic order parameter and the director results in corrections to all the Frank elastic constants. In the low-frequency limit (ω→0), the corrections to the Frank elastic constants K22 and K33 are the largest, and decrease to zero in the infinite-frequency limit. The correction to K11 is negative, and vanishes in both limits. The absolute value of the correction to K11 is the largest at frequencies in the megahertz range. It is shown that in oriented ncmatics the interaction of the smectic fluctuations and the director limits deviations of the director from the direction of preferred orientation, as a result of which relaxation of both inhomogeneous and homogeneous distortions of the director field can be observed. It is also shown that this gives rise to a frequency interval in the megahertz range in which shear waves begin to propagate in the nematic. The propagation speed of these waves is roughly a hundred times smaller than that of sound and strongly depends on the direction of propagation.

UR - http://www.scopus.com/inward/record.url?scp=33750100217&partnerID=8YFLogxK

U2 - 10.1134/1.558599

DO - 10.1134/1.558599

M3 - Article

AN - SCOPUS:33750100217

VL - 87

SP - 1098

EP - 1104

JO - Journal of Experimental and Theoretical Physics

JF - Journal of Experimental and Theoretical Physics

SN - 1063-7761

IS - 6

ER -