F. Semeria

A computer simulation of nematic droplets with radial boundary conditions

Abstract We present Monte Carlo simulations of nematic droplets with radial boundary conditions and we investigate the orientational order and the molecular organizations in these systems that mimic polymer dispersed liquid crystals (PDLC).

A DETAILED MONTE CARLO INVESTIGATION OF THE TRICRITICAL REGION OF A BIAXIAL LIQUID CRYSTAL SYSTEM

We study a lattice system of biaxial particles interacting with a second-rank anisotropic potential. We have performed detailed Monte Carlo calculations in the vicinity of the prolate–oblate dual value of molecular biaxiality. Our results confirm the second-order character of the transition in this limiting case.

Computer Simulations of Nematic Droplets with Toroidal Boundary Conditions

Abstract We present Monte Carlo simulations of nematic droplets with toroidal boundary conditions (TBC) and various anchoring strengths and we investigate the orientational order and the molecular organizations in these systems that mimic polymer dispersed liquid crystals (PDLC). PACS: 02.50 Monte Carlo studies PACS: 61.30.Jf Defects in liquid crystals PACS: 61.30.Gd Orientational order of liquid crystals PACS: 64.70.M Liquid Crystals phase transitions.

Monte Carlo simulations of model nematic droplets

Abstract We present Monte Carlo computer simulations of model nematic droplets with radial boundary conditions and various anchoring strengths and we investigate the orientational order and the molecular organizations in these systems that mimic polymer dispersed liquid crystals (PDLC). We find a hedgehog organization at high anchoring strengths and that an ordered domain is created in the droplet center at lower strengths.

Computer Simulations of Cylindrically Confined Nematics

Abstract A Monte Carlo simulation of a nematic Lebwohl-Lasher liquid crystal confined to a cylindrical pore is presented. We have calculated the ordering and the molecular organisation inside the cavity for cylinders of different size when homeotropic radial boundary conditions and different anchoring strengths are employed. We have not observed escaped radial configurations in the organisations obtained.

Monte Carlo study of the molecular organization in model nematic droplets. Field effects

Abstract The Monte Carlo technique is used to investigate the orientational order and the molecular organization of model nematic droplets with radial boundary conditions subject to an external field. The effect of varying field strength on these model systems of polymer dispersed liquid crystals (PDLC) is also investigated.

Can Spin Models Reproduce or Predict Experimental Results in PDLC

Abstract Lattice spin models are employed to study polymer dispersed liquid crystals (PDLC). We calculate polarized light textures and Deuterium NMR lineshapes from Monte Carlo computer simulations of model nematic droplets that mimic PDLC systems with radial, toroidal and bipolar boundary conditions. We also present microscopic properties such as order parameters across the sample obtained from the simulations. Our investigations of the PDLC systems include various temperatures and external applied fields both with positive and negative susceptivity anisotropy.

A MONTE CARLO SIMULATION OF A TWISTED NEMATIC LIQUID CRYSTAL DISPLAY

We present a Monte Carlo simulation of a model of a twisted nematic display on a lattice starting from purely microscopic interactions. We visualize the simulated display calculating optical textures under crossed polarizers corresponding to the Monte Carlo microscopic configurations. We also investigate the orientational order and the molecular organizations in the different regions of the lattice, introducing and calculating suitable order parameters.

Are Monte Carlo simulation results affected by sample shape? An investigation based on the Lebwohl-Lasher model

Abstract We investigate the sample shape dependence of periodic boundary conditions and cluster Monte Carlo simulation results for a Lebwohl-Lasher model with 1000 particles. We find marked differences between the two simulations, with pronounced shape effects when using periodic boundary conditions and we discuss their significance.

THREE-DIMENSIONAL VISUALIZATION OF MOLECULAR ORGANIZATION AND PHASE TRANSITIONS IN LIQUID CRYSTAL LATTICE MODELS*

An example of three-dimensional animation of Monte Carlo simulation results of liquid crystal lattice models is presented. Molecular configurations are obtained from Monte Carlo simulations on a VAX cluster and downloaded to a 486 personal computer. Visualization of molecular organizations and of their change at a phase transition is obtained by suitable colour coding of orientations and of other relevant physical information on the personal computer, and recorded on a VHS system using a genlock card. The animation sequences generated have a twofold interest: they are useful for educational purposes and, from a scientific point of view, they provide a tool for exploring a large amount of data and investigating the phenomena under study in a non-numerical way.