Q-tensor Model Research Articles

Electric field-induced fast nematic order dynamics

A strong electric field is able to induce transient and/or local biaxial states within a nematic calamitic phase, and the resultant nematic texture can be identified by the Landau–de Gennes Q-tensor theory. In this study we present a numerical Q-tensor model implemented with an adaptive moving-mesh finite element method, and this is able to describe the nematic order dynamics within a one-dimensional π-cell under the action of rapid electric pulses of different amplitudes. The proposed technique concentrates the grid points within regions of large ∇ Q , keeping the total number of nodes in the domain constant in order to avoid waste of computational effort in areas where spatial order variability is low. Both the nematic order and the electric current flowing across the cell are strongly dependent on the amplitude of the applied electric field. The evolution of biaxiality allows not only monostable elastic distortions to be described, but also textural transitions between nematic states with different topologies.

Implementation of Q-Tensor Model in Three-Dimensional Finite Element Method Simulator

In this paper, we report the first successful implementation, to the best of our knowledge of a Q-tensor model in a full three-dimensional (3-D) finite element method (FEM) simulator. Our FEM simulation code is based on the Landau–de Gennes Q-tensor model as well as the models of Dickmann and Nakagawa. The Oseen–Frank free-energy representation was formulated into a 3-D FEM code wherein tensor-order parameters as well as scalar-order parameters were employed for handling the defects and topological transitions such as splay-to-bend transition for the optically compensated bend (OCB) mode. The accuracy of our FEM simulator was verified using our simulation results with Mori's simulation data for the OCB mode. Splay-to-bend transition voltage was calculated to be 4 V according to the Q-tensor-model-based simulation while the conventional vector-model-based FEM solver showed 8 V. Our comparative study revealed that the vector model overestimates splay-to-bend voltage for the OCB mode.