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Sound-Propagation Gap In Fluid Mixtures, Supurna Sinha, M. Cristina Marchetti

Physics - All Scholarship

We discuss the behavior of the extended sound modes of a dense binary hard-sphere mixture. In a dense simple hard-sphere fluid the Enskog theory predicts a gap in the sound propagation at large wave vectors. In a binary mixture the gap is only present for low concentrations of one of the two species. At intermediate concentrations sound modes are always propagating. This behavior is not affected by the mass difference of the two species, but it only depends on the packing fractions. The gap is absent when the packing fractions are comparable and the mixture structurally resembles a metallic glass.

Mode-Coupling Theory Of The Stress-Tensor Autocorrelation Function Of A Dense Binary Fluid Mixture, Supurna Sinha, M. Cristina Marchetti

Physics - All Scholarship

We present a generalized mode-coupling theory for a dense binary fluid mixture. The theory is used to calculate molecular-scale renormalizations to the stress-tensor autocorrelation function (STAF) and to the long-wavelength zero-frequency shear viscosity. As in the case of a dense simple fluid, we find that the STAF appears to decay as t−3/2 over an intermediate range of time. The coefficient of this long-time tail

is more than two orders of magnitude larger than that obtained from conventional mode-coupling theory. Our study focuses on the effect of compositional disorder on the decay of the STAF in a dense mixture.