Rotational and Translational Phonon Modes in Glasses Composed of Ellipsoidal Particles

Abstract

The effects of particle shape on the vibrational properties of colloidal glasses are studied experimentally. 'Ellipsoidal glasses' are created by stretching polystyrene spheres to different aspect ratios and then suspending the resulting ellipsoidal particles in water at high packing fraction. By measuring displacement correlations between particles, we extract vibrational properties of the corresponding "shadow" ellipsoidal glass with the same geometric configuration and interactions as the 'source' suspension but without damping. Low frequency modes in glasses composed of ellipsoidal particles with major/minor axis aspect ratios $\sim$1.1 are observed to have predominantly rotational character. By contrast, low frequency modes in glasses of ellipsoidal particles with larger aspect ratios ($\sim$3.0) exhibit a mix of rotational and translational character. All glass samples were characterized by a distribution of particles with different aspect ratios. Interestingly, even within the same sample it was found that small-aspect-ratio particles participate relatively more in rotational modes, while large-aspect-ratio particles tend to participate relatively more in translational modes.

6 Pages, 6 Figures

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Cited by in corpus (8)

• Glass transitions in two-dimensional suspensions of colloidal ellipsoids
• Measurement of correlations between low-frequency vibrational modes and particle rearrangements in quasi-two-dimensional colloidal glasses
• Tetrahedral colloidal clusters from random parking of bidisperse spheres
• Tracking Rotational Diffusion of Colloidal Clusters
• Phonons in two-dimensional soft colloidal crystals
• Relaxation dynamics in a binary hard-ellipse liquid
• Vibrational properties of two-dimensional dimer packings near the jamming transition
• Theory of rigidity and numerical analysis of density of states of two-dimensional amorphous solids with dispersed frictional grains in the linear response regime