Large Scale Lattice-Boltzmann Simulation of Liquid Crystals

I will present results from our large scale lattice-Boltzmann simulations of Blue Phases. Blue Phases (BPs) are equilibrium phases in chiral nematic liquid crystals containing a lattice of disclinations. They are found in thermotropic liquid crystals close to the cholesteric-isotropic transition. While older experiments typically observed BPs only in a very narrow temperature range of about 1 K, more recent ones have created BPs over a strikingly wide temperature range of 50 K including room temperature. This opens up a completely new field of possible future applications. We calculated the phase diagram of BPs in external electric fields and found that for increasing field strengths the phase diagram exhibits increasingly large domains of planar and three-dimensional hexagonal BPs. By simulating quenches from the cholesteric phase into the BP region we probably found the structure of BPIII (also known as blue fog), which has remained a mystery for the last 25 years. Finally I will show results for BPI and BPII domain growth in either cholesteric or isotropic environment. The seeds don't grow directly into the ordered equilibrium phases, but rather in an unexpected fashion. Our findings indicate that initially a fast proliferation of defects takes place, whereas the growth into the ordered equilibrium phases occurs on much longer time scales.