Study On The Chiral-broken Of Nematic Liquid Crystals By Landau-de Gennes Theory

The twisted and escaped radial?TER?configuration can exhibit in cylindrical capillaries with nematic liquid crystals.Because of the independence of the handedness and escape directions,two degenerate escape directions and two degenerate senses of handness?right/left?in the TER configuration lead to a rich phenomenology of defects.Based on the Landau-de Gennes theory,we have investigated the defect which is found to arise when the two opposite escape directions of the heterochiral TER configuration diverge?converge?,using finite-difference iterative method.The variation of the structure with elastic anisotropy is also studied.The mainly studies are listed as follows:Firstly,we studied the defect which is found to arise when the two opposite escape directions of the heterochiral TER configuration diverge.A hyperbolic defect which contains a planar radial structure appears in this configuration.Then,with the changing of the elastic anisotropy,the system structure changes.A?-1/2?defect ring formed when the system is elastic isotropic?L₂ L₁=0?.Meanwhile,a hyperbolic defect which contains a planar radial structure formed when the system is elastic anisotropic?L₂ L₁>0?.The thickness of planar radial structure increased and the defect developed as the elastic anisotropy of system increasing.Secondly,we studied the defect which is found to arise when two opposite escape directions of the heterochiral TER configuration converge.A?+1/2?radial defect ring appears in this configuration.Then we investigated the change of structure with elastic anisotropy?L₂ L₁?changing.The structure and the shape of defects have no significant change in the process?L₂ L₁=0²8?,while the radial of the defect ring increases.At last,a new defect structure which is based on the structure that two opposite escape directions of the heterochiral TER configuration converge is studied.We found that a new structure generated when the elastic anisotropy was large enough.The new defect is presents when L₂ L₁?7,and disappears when L₂ L₁<7.In the new structure,a new defect is formed when two homochiral and escape converging TER configurations coupled,and the new defects on both sides of the nucleus have different chirality.Any single side of the new defect is unstable in the experiment.Spontaneous distortion is a prerequisite for the stability of new defects,and free boundary has no effect on it.