Volume viscosity and ultrasonic relaxation of ethanol-water mixtures studied by molecular dynamics simulations

The volume viscosity of ethanol-water mixtures at various compositions was calculated by means of equilibrium molecular dynamics simulations, and the results were compared with acoustic experiments. The volume viscosity exhibited a strong maximum around the ethanol mole fraction of 0.27, which is in agreement with experiments. The relaxation in the 100 ps regime, which had been revealed by ultrasonic spectroscopy, was also reproduced. Analysis of the two-body density and the adiabatic pressure fluctuation demonstrated that the large volume viscosity of the mixture originates from the long-range concentration fluctuation.

Automated summary

The volume viscosity of ethanol-water mixtures was calculated and compared with acoustic experiments. The study found that the volume viscosity exhibited a strong maximum at an ethanol mole fraction of 0.27, which agrees with experimental results. The simulations also reproduced the relaxation observed in ultrasonic spectroscopy within the 100 ps regime.