TY - JOUR

T1 - Hysteresis and Freedericksz thresholds for twisted states in chiral nematic liquid crystals

T2 - Minimum-energy path approach

AU - Тенищев, Семён Станиславович

AU - Тамбовцев, Иван Михайлович

AU - Киселев, Алексей Дониславович

AU - Уздин, Валерий Моисеевич

N1 - Publisher Copyright: © 2020 Elsevier B.V.

PY - 2021/3/1

Y1 - 2021/3/1

N2 - We study minimum-energy pathways (MEPs) between the branches of metastable helical structures in chiral nematic liquid crystals (CNLCs) subjected to the electric field applied across the cell. By performing stability analysis we have found that, for the branches with non-vanishing half-turn number, the threshold (critical) voltage of the Fréedericksz transition is an increasing function of the free twisting wave number. The curves for the threshold voltage depend on the elastic anisotropy and determine the zero-field critical free twisting number where the director out-of-plane fluctuations destabilize the CNLC helix. For each MEP passing through a first order saddle point we have computed the energy barrier as the energy difference between the saddle-point and the initial structures at different values of the applied field. In our calculations, where the initial approximation for a MEP at the next step was determined by the MEP obtained at the previous step, the electric field dependence of the energy barrier is found to exhibit the hysteresis. This is the hysteresis of electrically driven transition of the saddle-point configuration between the planar and the tilted structures involving out-of-plane director deformations. It turned out that, by contrast to the second-order Fréedericksz transition, this transition is first order and we have studied how it depends on the zenithal anchoring energy strength.

AB - We study minimum-energy pathways (MEPs) between the branches of metastable helical structures in chiral nematic liquid crystals (CNLCs) subjected to the electric field applied across the cell. By performing stability analysis we have found that, for the branches with non-vanishing half-turn number, the threshold (critical) voltage of the Fréedericksz transition is an increasing function of the free twisting wave number. The curves for the threshold voltage depend on the elastic anisotropy and determine the zero-field critical free twisting number where the director out-of-plane fluctuations destabilize the CNLC helix. For each MEP passing through a first order saddle point we have computed the energy barrier as the energy difference between the saddle-point and the initial structures at different values of the applied field. In our calculations, where the initial approximation for a MEP at the next step was determined by the MEP obtained at the previous step, the electric field dependence of the energy barrier is found to exhibit the hysteresis. This is the hysteresis of electrically driven transition of the saddle-point configuration between the planar and the tilted structures involving out-of-plane director deformations. It turned out that, by contrast to the second-order Fréedericksz transition, this transition is first order and we have studied how it depends on the zenithal anchoring energy strength.

KW - Chiral nematic liquid crystal

KW - Fréedericksz transition

KW - Hysteresis

KW - Minimum-energy path

KW - Freedericksz transition

UR - http://www.scopus.com/inward/record.url?scp=85098952457&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/226e62ad-79d4-3cfd-9aa9-b3db6a841459/

U2 - 10.1016/j.molliq.2020.115242

DO - 10.1016/j.molliq.2020.115242

M3 - Article

VL - 325

JO - Journal of Molecular Liquids

JF - Journal of Molecular Liquids

SN - 0167-7322

M1 - 115242

ER -