Crystallization of a Quasi-Two-Dimensional Granular Fluid

Abstract

We experimentally investigate the crystallization of a uniformly heated quasi-2D granular fluid as a function of the filling fraction. Our experimental results for the Lindemann melting criterion, the radial distribution function, the bond order parameter, and the statistics of topological changes at the particle level are the same as those found in simulations of equilibrium hard disks. This direct mapping suggests that the study of equilibrium systems can be effectively applied to study nonequilibrium steady states such as those found in our driven and dissipative granular system.

Two features at the two-dimensional freezing transitions

“…Criterion (3) has a 5% ambiguity around the freezing points for hard disks, 8 Lennard-Jones systems 7 and colloidal microgel spheres with short-range repulsions. 12 Criterion (4) consistently underestimates the freezing points for hard disks 9,13 and microgels by 6% volume fractions. 12 Criterion (5) has been tested in hard disks, 14 2D and 3D Lennard-Jones systems 14,15 and even rods at nematic-smectic transitions in 3D, 16 but was found to be more ambiguous in systems with short-range repulsions, 17 and attractions 15 at high densities.…”

“…12 2D freezing has been experimentally studied in colloids, 23,24 dusty plasmas, 25,26 and driven granular systems. 13 These experiments focused on local structures, dynamics, and the initial nucleation processes rather than the freezing criteria. Recently, some of us experimentally tested the freezing criteria (1)-(4) in a thermal system for the first time.…”

Crystallisation in a granular material

“…The growing crystalline structure is shaped by the competition between the input of external energy Àuxes and the dissipation at the grain contacts. Numerous experiments have reported analogies between this out of equilibrium crystallisation and a thermodynamic transition [3,4]. An entropic mechanism driving this ordering despite the highly dissipative context is still unknown [3].…”

Viscoelasticity of 2D Liquids Quantified in a Dusty Plasma Experiment

“…Two-dimensional (2D) physical systems include electrons on a liquid helium surface [1], colloids [2], granular fluids [3], and dusty plasmas [4]. In experiments and simulations, elastic properties, such as transverse waves [5,6], and transport properties, such as viscosity η [7][8][9], have been studied.…”

“…As in colloids [2] and granular fluids [3], they allow video microscopy to track the x i and v i of individual particles. They also provide both elastic and viscous effects.…”