Abstract
We employ nonequilibrium molecular dynamics simulations to investigate the structure and dynamics of a cholesteric liquid crystal confined between atomically corrugated solid walls. By choosing walls normal to the helical axis, we can study systems with an arbitrary cholesteric pitch without exposing the cholesteric helix to a spurious stress. We investigate the effects of local heating and flow and their joint effects. A steady-state laminar Poiseuille flow is initiated by means of an external body force. Flow alone (i.e., without local heating) in a direction normal to the helical axis does not affect the cholesteric pitch. If the liquid crystal is heated in a small region, the cholesteric helix becomes unstable and melts locally. However, if local heating and flow are combined, a nontrivial synergistic effect is observed in that the helical structure recuperates the better, the higher the speed of the flow is.
Highlights
Cholesteric or chiral nematic liquid crystals are fluid systems exhibiting considerable order [1, 2], because of their directional molecular forces [3]
Because we are interested in simulating systems in stationary nonequilibrium states we need to drive these systems by applying an external body force
The present study focuses on the combined impact of steady-state flow and local heating on the helical structure of a cholesteric phase
Summary
Cholesteric or chiral nematic liquid crystals are fluid systems exhibiting considerable order [1, 2], because of their directional molecular forces [3]. In cholesterics, these molecular forces induce a twist of the molecular symmetry axes of neighboring molecules. Cholesteric liquid crystals have been the first mesophase discovered [11], and continue to produce important results in optics [12] and physical chemistry due to the possibility of obtaining a highly refined control of light-matter interactions [10, 13] Owing to their structure, cholesterics’ dynamics can be very complex and deserve further investigation. The factor of 4 is included for reasons that will become clear shortly
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