Effect of phase shift between geometrical and chemical patterning in nematic liquid crystal cells: A Monte Carlo study

• Published in: Computational materials science 2014-09, Vol.92, p.238-243
• Main Authors: Dontabhaktuni, Jayasri, Jose, Regina, Murthy, K.P.N., Sastry, V.S.S.
• Format: Article
• Language: English
• Subjects: Angles (geometry); Biaxiality; Camber; Condensed matter: structure, mechanical and thermal properties; Confined nematic liquid crystals; Entropic sampling; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Geometrically and chemically patterned substrates; Liquid crystals; Mathematical analysis; Monte Carlo methods; Nematic; Phase shift; Physics; Specific phase transitions; Tilt; Transitions in liquid crystals; Wang-Landau algorithm
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2014.05.037

[Display omitted] •Liquid crystals confined to geometrical and chemical patterns are studied employing entropic sampling methods.•Our simulations show earlier continuum predictions are asymptotic limit of the realistic nematics at very low temperatures.•Phase shift between geometrical and chemical patterns brings about interesting director symmetries.•Reasonably high phase biaxiality is seen as a result of the phase shift between the patterns. Thin films of nematic liquid crystals confined to geometrically as well as chemically patterned substrate at one end and a planar substrate with strong anchoring at the other are studied employing non-Boltzmann Monte Carlo methods. We investigate the effect of temperature on the director structures as the system goes through the isotropic-nematic phase transition. The low temperature results show significant deviations from the phase diagram predicted within the continuum approximation, depicted as a function of the tilt angle at the top substrate and the thickness of the cell. Onset of phase biaxiality is observed at very low temperatures, and it increases as the tilt angle at the top substrate is increased, moving away from the normal to the substrate. A phase shift introduced between the geometrical and chemical patterns at the other end also enhances the phase biaxiality of the system to a fairly high value. This seems to provide a convenient experimentally tunable parameter for controlling the symmetry of the director structures.