Computer simulation of nematic reentrance in a simple molecular model.

We report a computer simulation study of a system of parallel hard ellipsoids with attractive interactions represented by a spherically symmetric square well of range lamba. For suitable values of the results are consistent with the sequence of phases nematic (N), smectic-A (SmA), reentrant nematic (N(re)), and crystal (Cr) under pressure. Both the N-SmA and the SmA-N(re) transitions are found to be first order or continuous depending on temperature.

Density functional theory and simulation of the columnar phase of a system of parallel hard ellipsoids with attractive interactions.

A simple molecular model consisting of parallel hard oblate ellipsoids with superimposed square-well attractive interactions of variable range is considered for the study of the phase behavior of thermotropic discotic molecules. A density functional theory appropriate for nonuniform fluids is formulated in which the hard-core contributions to the free energy are treated within a nonlocal weighted-density approximation (WDA) while the attractive contributions are treated at a mean-field level. It is shown that the columnar phase becomes stable relative to the nematic phase at fluid densities for a range of values of the range of the attractive well.

Smectic phase in a system of hard ellipsoids with isotropic attractive interactions.

The smectic phase is studied for a thermotropic fluid model consisting of aligned hard ellipsoids with superimposed square-well attractive interactions of variable range. The system is analyzed using a density functional theory in which the hard-core contributions to the free-energy functional are treated within a nonlocal weighted density approximation and the attractive contributions are considered at a mean-field level. In the absence of attractions the model reduces, under appropriate scaling, to a fluid of hard spheres and therefore does not exhibit smectic ordering.

Stability of smectic phases in the Gay-Berne model.

We present a detailed computer simulation study of the phase behavior of the Gay-Berne liquid crystal model with molecular anisotropy parameter kappa=4.4. According to previous investigations: (i) this model exhibits isotropic (I), smectic-A (Sm-A), and smectic-B (Sm-B) phases at low pressures, with an additional nematic (N) phase between the I and Sm-A phases at sufficiently high pressures; (ii) the range of stability of the Sm-A phase turns out to be essentially constant when varying the pressure, whereas other investigations seem to suggest a pressure-dependent Sm-A range; and (iii) the range of stability of the Sm-B phase remains unknown, as its stability with respect to the crystal phase has not been previously considered.

An accurate density functional theory for the vapor-liquid interface of associating chain molecules based on the statistical associating fluid theory for potentials of variable range.

A Helmholtz free energy density functional is developed to describe the vapor-liquid interface of associating chain molecules. The functional is based on the statistical associating fluid theory with attractive potentials of variable range (SAFT-VR) for the homogenous fluid [A. Gil-Villegas, A.