Disappearance of the hexatic phase in a binary mixture of hard disks

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 specialized Monte Carlo simulations to elucidate the phase behavior of a system of large ($l$) and small ($s$) disks with diameter ratio ${\sigma }_l/{\sigma }_s=1.4$. We find that as small disks are added 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, $c\lesssim 1\%$, 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.

5 pages plus 8 pages supplementary material

References in corpus (1)

• 2D Melting: From Liquid-Hexatic Coexistence to Continuous Transitions

Cited by in corpus (11)

• Colloidal Hard Spheres: Triumphs, Challenges and Mysteries
• Attraction tames two-dimensional melting: from continuous to discontinuous transitions
• Phase behaviour of Lennard-Jones particles in two dimensions
• Accurate determination of the translational correlation function of two-dimensional solids
• Connecting glass-forming ability of binary mixtures of soft particles to equilibrium melting temperatures
• Topographic control of order in quasi-2D granular phase transitions
• Two-Dimensional Melting of two- and three-component mixtures
• Demixing and tetratic ordering in some binary mixtures of hard superellipses
• Lateral depletion effect on two-dimensional ordering of bacteriorhodopsins in a lipid bilayer: A theoretical study based on a binary hard-disk model
• Scanning-probe and information-concealing machine learning intermediate hexatic phase and critical scaling of solid-hexatic phase transition in deformable particles
• Data-driven criterion for the solid-liquid transition of two-dimensional self-propelled colloidal particles far from equilibrium