A two dimensional glass: microstructure and dynamics of a 2D binary mixture

A 2D equimolar binary mixture of r(-12) soft disks with a diameter ratio of 1.4 is shown, via constant pressure-temperature molecular dynamics simulations, to exhibit, on cooling, a wide range of properties of glass-forming liquids. At all temperatures studied, the liquid is found to be kinetically stable with respect to crystallisation over time scales many times that of the structural relaxation. The temperature at which the 'step' in the incoherent scattering function first appears is identified as an important crossover in relaxation mechanisms. Cooling below this temperature results in the development of kinetic heterogeneity and the breakdown in scaling between the structural relaxation time and the diffusion constant. Direct visualisation provides a measure of increasing cooperativity and insight into the nature of the collective motions. (C) 1998 Elsevier Science B.V. All rights reserved.