title: Glass formation in a mixture of hard disks and hard ellipses.
abstract: We present an event-driven molecular dynamics study of glass formation in two-dimensional binary mixtures composed of hard disks and hard ellipses, where both types of particles have the same area. We demonstrate that characteristic glass-formation behavior appears upon compression under appropriate conditions in such systems. In particular, while a rotational glass transition occurs only for the ellipses, both types of particles undergo a kinetic arrest in the translational degrees of freedom at a single density. The translational dynamics for the ellipses is found to be faster than that for the disks within the same system, indicating that shape anisotropy promotes the translational motion of particles. We further examine the influence of mixture's composition and aspect ratio on the glass formation. For the mixtures with an ellipse aspect ratio of k = 2, both translational and rotational glass transition densities decrease with increasing the disk concentration at a similar rate, and hence, the two glass transitions remain close to each other at all concentrations investigated. By elevating k, however, the rotational glass transition density diminishes at a faster rate than the translational one, leading to the formation of an orientational glass for the ellipses between the two transitions. Our simulations imply that mixtures of particles with different shapes emerge as a promising model for probing the role of particle shape in determining the properties of glass-forming liquids. Furthermore, our work illustrates the potential of using knowledge concerning the dependence of glass-formation properties on mixture's composition and particle shape to assist in the rational design of amorphous materials.
authors.affiliation: James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Wen-Sheng
authors.initials: WS
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China.
authors.forename: Xiaozheng
authors.initials: X
authors.lastname: Duan
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China.
authors.forename: Zhao-Yan
authors.initials: ZY
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China.
authors.forename: Li-Jia
authors.initials: LJ
authors.lastname: An