Eur. Phys. J. B 72, 225-231 (2009)
https://doi.org/10.1140/epjb/e2009-00333-x

The isotropic-to-nematic transition in a two-dimensional fluid of hard needles: a finite-size scaling study

Institute of Theoretical Physics, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

Corresponding author: ^a rlcvink@gmail.com

Received: 30 June 2009
Revised: 3 September 2009
Published online: 10 October 2009

Abstract

The isotropic-to-nematic transition in a two-dimensional fluid of hard needles is studied using grand canonical Monte Carlo simulations, multiple histogram reweighting, and finite size scaling. The transition is shown to be of the Kosterlitz-Thouless type, via a direct measurement of the critical exponents η and β, of the susceptibility and order parameter, respectively. At the transition, η = 1/4 and β = 1/8 are observed, in excellent agreement with Kosterlitz-Thouless theory. Also the shift in the chemical potential of the nematic susceptibility maximum with system size is in good agreement with theoretical expectations. Some evidence of singular behavior in the density fluctuations is observed, but no divergence, consistent with a negative specific heat critical exponent. At the transition, a scaling analysis assuming a conventional critical point also gives reasonable results. However, the apparent critical exponent β_eff obtained in this case is not consistent with theoretical predictions.