Computer simulation study of a mesogenic lattice model based on long-range dispersion interactions

TL;DR

This study uses Monte Carlo simulations to explore a lattice model with long-range dispersion interactions, revealing the emergence of cubatic order without nematic phases, contrasting with models with short-range interactions.

Contribution

It introduces a new lattice model with long-range dispersion interactions that exhibits cubatic order, providing insights into orientational phases beyond traditional nematic states.

Findings

Long-range dispersion interactions induce cubatic order.

Nearest-neighbor models produce nematic order, unlike the long-range model.

The model does not exhibit nematic phases, only cubatic order.

Abstract

In contrast to thermotropic biaxial nematic phases, for which some long sought for experimental realizations have been obtained, no experimental realizations are yet known for their tetrahedratic and cubatic counterparts,involving orientational orders of ranks 3 and 4, respectively, also studied theoretically over the last few decades. In previous studies, cubatic order has been found for hard-core or continuous models consisting of particles possessing cubic or nearly-cubic tetragonal or orthorhombic symmetries; in a few cases, hard-core models involving uniaxial ($D_{\infty h}-$symmetric) particles have been claimed to produce cubatic order as well. Here we address by Monte Carlo simulation a lattice model consisting of uniaxial particles coupled by long-range dispersion interactions of the London-De Boer-Heller type; the model was found to produce no second-rank nematic but only fourth-rank cubatic order, in contrast to the nematic behavior long known for its counterpart with interactions truncated at nearest-neighbor separation.