Disappearance of the Hexatic Phase in a Binary Mixture of Hard Disks

John Russo and Nigel B. Wilding
Phys. Rev. Lett. 119, 115702 – Published 14 September 2017
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Abstract

Recent studies of melting in hard disks have confirmed the existence of a hexatic phase occurring in a narrow window of density which is separated from the isotropic liquid phase by a first-order transition, and from the solid phase by a continuous transition. However, little is known concerning the melting scenario in mixtures of hard disks. Here we employ tailored Monte Carlo simulations to elucidate the phase behavior of a system of large (l) and small (s) disks with diameter ratio σl/σs=1.4. We find that as small disks are introduced to a system of large ones, the stability window of the hexatic phase shrinks progressively until the line of continuous transitions terminates at an end point beyond which melting becomes a first-order liquid-solid transition. This occurs at surprisingly low concentrations of the small disks, c1%, emphasizing the fragility of the hexatic phase. We speculate that the change to the melting scenario is a consequence of strong fractionation effects, the nature of which we elucidate.

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  • Received 15 June 2017

DOI:https://doi.org/10.1103/PhysRevLett.119.115702

© 2017 American Physical Society

Physics Subject Headings (PhySH)

Statistical Physics & Thermodynamics

Authors & Affiliations

John Russo*

  • School of Mathematics, University of Bristol, Bristol BS8 1TW, United Kingdom

Nigel B. Wilding

  • Department of Physics, University of Bath, Bath BA2 7AY, United Kingdom

  • *john.russo@bristol.ac.uk
  • n.b.wilding@bath.ac.uk

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Issue

Vol. 119, Iss. 11 — 15 September 2017

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