C. Chiccoli

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(3) ENEA} Viale Ercolani 8} 40138 Bologna} Italy •. 1. Introduction. Liquid crystals (LC) form a state of matter intermediate between solids and liquids [1] as indicated by their contradictory name. The main characteristic of liquid crystals at molecular level is that they possess orientational order, together with a traslational mobility similar to that of(More)
We have determined the phase diagram for a lattice system of biaxial particles interacting with a second rank anisotropic potential using Monte Carlo simulations for a number of values of the molecular biaxiality. We find increasing differences from mean field theory as the biaxiality increases. We have also calculated for the first time the full set of(More)
Monte Carlo and theoretical studies of thin 3D films of biaxial and uniaxial nematics with tangential boundary conditions show distinct differences in structure and evolution of topological defects. In the uniaxial films, defects of strength k=+/-1 are point defects that bear no bulk singularity and disappear by annihilation with each other. In the biaxial(More)
It is now generally accepted that even low amounts of quenched disorder disrupt long-range order in anisotropic systems with continuous symmetry. However, very little is known on the key item of the nature of the residual order, if any, and particularly if this has quasi-long-range or truly-short-range character. Here we address this problem both(More)
Monte Carlo (MC) simulations based exclusively on nearest-neighbor intermolecular interactions reveal the existence of stable long-range deformations and topological defects in a thin nematic film confined between two surfaces with antagonistic (normal and tangential) molecular orientations. Thus the MC technique allows one to describe a delicate balance of(More)
We confirm by Monte Carlo simulations of a Lebwohl-Lasher lattice spin model the existence of a biaxially ordered nonbent structure in a liquid-crystalline cell subject to opposing boundary conditions. We report on the observation of the bending transition from the biaxial to the bent-director structure when the temperature of the system is lowered. The(More)
We present a combined experimental and Monte Carlo study of a nematic phase in the presence of quenched disorder. The turbidity of a nematic liquid crystal embedded in a porous polymer membrane is measured under different applied field conditions for field-cooled and zero-field-cooled samples. We find that a significant permanent alignment of the nematic(More)
We study a lattice system of biaxial particles interacting with a second rank anisotropic potential by means of Monte Carlo simulations over a wide distributed network. We use the Condor processing system installed on the Italian Nuclear Physics Institute computer network. We have done calculations for a large number of different values of molecular(More)
We analyze the dynamical aspects of molecular ordering in nematic droplets with radial and bipolar boundary conditions—as encountered in polymer-dispersed liquid crystals—by calculating and interpreting the corresponding 2 H NMR spectra. In particular, we focus on effects of molecular motion such as fluctuations of molecular long axes and translational(More)