Glass Transition in a Polydispersed Colloidal System
Glasses are important in many industrial applications. They are formed if crystallization is avoided upon cooling or increasing density. However, the physical factors controlling the ease of vitrification and nature of the glass transition remain elusive. We use numerical simulations of polydisperse hard disks to tackle both of these longstanding questions. Here we systematically control the polydispersity in two-dimensional colloidal simulations, i.e., the strength of frustration effects on crystallization. We demonstrate that medium-range crystalline order grows in size and lifetime with an increase in the colloid volume fraction or a decrease in polydispersity (or, frustration). We find a direct relation between medium-range crystalline ordering and the slow dynamics that characterizes the glass transition. This suggests an intriguing scenario that the strength of frustration controls both the ease of vitrification and nature of the glass transition. Vitrification may be a process of hidden crystalline ordering under frustration. This not only provides a physical basis for glass formation, but also an answer to a longstanding question on the structure of amorphous materials: ''order in disorder'' is an intrinsic feature of a glassy state of material. Thus our scenario makes a natural connection between structure and dynamics in glass-forming materials.
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