Substrate induced freezing, melting and depinning transitions in two-dimensional liquid crystalline systems

We use molecular dynamics simulations to investigate the ordering phenomena in two-dimensional (2D) liquid crystals over the one-dimensional periodic substrate (1DPS). We have used Gay-Berne (GB) potential to model the interaction between a pair of liquid crystalline (LC) particles. The underlying substrate potential with which the GB particles interact varies sinusoidally in one direction only. At a given temperature and density of the GB system, we varied the substrate's periodicity (a(s)) but fixed the substrate strength. We observed that with a small value of a(s), an underlying substrate helps to stabilize a disordered LC nematic phase to a 2D solid phase. However, for an intermediate range of a(s), the system melts and transitions to a modulate-smectic. Finally, with a further increase in a(s), the system undergoes a structural depinning transition and returns to an LC nematic phase like a free system with no substrate. We argue that a three-way interplay of the energies arising from orientation-dependent particle-particle and particle-substrate interaction makes it possible for the system to undergo substrate-periodicity-dependent multiple phase transitions in the GB LC system.

Automated summary

We investigated the ordering phenomena in two-dimensional liquid crystals over a one-dimensional periodic substrate using molecular dynamics simulations. The periodicity of the substrate plays a crucial role in the phase transitions of the liquid crystal system, with small periodicity stabilizing a disordered phase, intermediate periodicity leading to a modulated smectic phase, and larger periodicity causing the system to return to a nematic phase similar to a free system without substrate.