Friday, June 14, 2013

1306.3188 (Tim Still et al.)

Phonon Dispersion and Elastic Moduli of Two-Dimensional Disordered
Colloidal Packings of Soft-Particles with Frictional Interactions

Tim Still, Carl P. Goodrich, Ke Chen, Peter J. Yunker, Samuel Schoenholz, Andrea J. Liu, A. G. Yodh
Particle tracking and displacement covariance matrix techniques are employed to investigate the phonon dispersion relations of two-dimensional colloidal glasses composed of soft, thermoresponsive microgel particles whose temperature-sensitive size permits in situ variation of particle packing fraction. Bulk modulus, B, and shear modulus, G, of the colloidal glasses are extracted from the dispersion relations as a function of packing fraction. The ratio G/B is found to agree quantitatively with predictions for jammed packings of frictional soft particles with only one parameter required for the fit - the packing fraction for the onset of jamming in the limit of infinite friction. In addition, G and B individually agree with numerical predictions for frictional particles. This remarkable level of agreement enabled us to extract the inter-particle friction coefficient and an energy scale for the inter-particle interaction from the individual elastic constants.
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