Complete integrability and equilibrium thermodynamics of biaxial nematic systems with discrete orientational degrees of freedom

Fuente: arXiv
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Main Authors: De Matteis, Giovanni, Giglio, Francesco, Moro, Antonio
Format: Preprint
Published: 2023
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author De Matteis, Giovanni
Giglio, Francesco
Moro, Antonio
author_facet De Matteis, Giovanni
Giglio, Francesco
Moro, Antonio
contents We study a discrete version of a biaxial nematic liquid crystal model with external fields via an approach based on the solution of differential identities for the partition function. In the thermodynamic limit, we derive the free energy of the model and the associated closed set of equations of state involving four order parameters, proving the integrability and exact solvability of the model. The equations of state are specified via a suitable representation of the orientational order parameters, which imply two-order parameter reductions in the absence of external fields. A detailed exact analysis of the equations of state reveal a rich phase diagram where isotropic versus uniaxial versus biaxial phase transitions are explicitly described, including the existence of triple and tricritical points. Results on the discrete models are qualitatively consistent with their continuum analog. This observation suggests that, in more general settings, discrete models may be used to capture and describe phenomena that also occur in the continuum for which exact equations of state in closed form are not available.
format Preprint
id arxiv_https___arxiv_org_abs_2309_13293
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Complete integrability and equilibrium thermodynamics of biaxial nematic systems with discrete orientational degrees of freedom
De Matteis, Giovanni
Giglio, Francesco
Moro, Antonio
Exactly Solvable and Integrable Systems
Soft Condensed Matter
We study a discrete version of a biaxial nematic liquid crystal model with external fields via an approach based on the solution of differential identities for the partition function. In the thermodynamic limit, we derive the free energy of the model and the associated closed set of equations of state involving four order parameters, proving the integrability and exact solvability of the model. The equations of state are specified via a suitable representation of the orientational order parameters, which imply two-order parameter reductions in the absence of external fields. A detailed exact analysis of the equations of state reveal a rich phase diagram where isotropic versus uniaxial versus biaxial phase transitions are explicitly described, including the existence of triple and tricritical points. Results on the discrete models are qualitatively consistent with their continuum analog. This observation suggests that, in more general settings, discrete models may be used to capture and describe phenomena that also occur in the continuum for which exact equations of state in closed form are not available.
title Complete integrability and equilibrium thermodynamics of biaxial nematic systems with discrete orientational degrees of freedom
topic Exactly Solvable and Integrable Systems
Soft Condensed Matter
url https://arxiv.org/abs/2309.13293