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Autori principali: Franosch, Thomas, De Michele, Cristiano, Schilling, Rolf
Natura: Preprint
Pubblicazione: 2025
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Accesso online:https://arxiv.org/abs/2505.14145
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author Franosch, Thomas
De Michele, Cristiano
Schilling, Rolf
author_facet Franosch, Thomas
De Michele, Cristiano
Schilling, Rolf
contents For a fluid of convex hard particles, characterized by a length scale $σ_\text{min}$ and an anisotropy parameter $ε$, we develop a formalism allowing one to relate thermodynamic quantities to the body's shape. In a first step its thermodynamics is reduced to that of spherical particles. The latter have a hard core of diameter $σ_\text{min }$ and a soft shell with a thickness $εσ_\text{min}/2$. Besides their hard core repulsion at $σ_\text{min }$ they interact by effective entropic forces which will be calculated. Based on this mapping, a second step provides a perturbative method for the systematic calculation of thermodynamic quantities with the shape anisotropy $ε$ as smallness parameter. In leading order in $ε$, the equation of state is derived as a functional of the particle's shape. To illustrate these findings, they are applied to a one- and two-dimensional fluid of ellipses and compared with results from different analytical approaches, and our computer simulations. The mapping to spherical particles also implies that any phase transition of spherical particles, e.g., the liquid-hexatic transition, also exists for the nonspherical ones, and shifts linearly with $ε$ for weak shape anisotropy. This is supported by our Monte-Carlo simulation.
format Preprint
id arxiv_https___arxiv_org_abs_2505_14145
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Relating thermodynamic quantities of convex-hard-body fluids to the body's shape
Franosch, Thomas
De Michele, Cristiano
Schilling, Rolf
Statistical Mechanics
For a fluid of convex hard particles, characterized by a length scale $σ_\text{min}$ and an anisotropy parameter $ε$, we develop a formalism allowing one to relate thermodynamic quantities to the body's shape. In a first step its thermodynamics is reduced to that of spherical particles. The latter have a hard core of diameter $σ_\text{min }$ and a soft shell with a thickness $εσ_\text{min}/2$. Besides their hard core repulsion at $σ_\text{min }$ they interact by effective entropic forces which will be calculated. Based on this mapping, a second step provides a perturbative method for the systematic calculation of thermodynamic quantities with the shape anisotropy $ε$ as smallness parameter. In leading order in $ε$, the equation of state is derived as a functional of the particle's shape. To illustrate these findings, they are applied to a one- and two-dimensional fluid of ellipses and compared with results from different analytical approaches, and our computer simulations. The mapping to spherical particles also implies that any phase transition of spherical particles, e.g., the liquid-hexatic transition, also exists for the nonspherical ones, and shifts linearly with $ε$ for weak shape anisotropy. This is supported by our Monte-Carlo simulation.
title Relating thermodynamic quantities of convex-hard-body fluids to the body's shape
topic Statistical Mechanics
url https://arxiv.org/abs/2505.14145