Density scaling of the diffusivity in viscous liquids: Identification of the scaling exponent with the pressure derivative of the isothermal bulk modulus

TL;DR

This paper revisits the density scaling of diffusivity in viscous liquids, demonstrating that the scaling exponent equals the pressure derivative of the isothermal bulk modulus, with implications for understanding liquid dynamics.

Contribution

It establishes a direct link between the density scaling exponent and the pressure derivative of the bulk modulus without assuming their interconnection with the Gruneisen parameter.

Findings

The scaling exponent equals the pressure derivative of the bulk modulus.

The isothermal bulk modulus increases linearly with pressure.

Potential connection between the scaling exponent and the Gruneisen parameter.

Abstract

A density scaled diffusivity function for viscous liquids derived earlier [Phys. Rev. E 79, 032501 (2009)] is revisited, based on an improved equation of state assuming that the isothermal bulk modulus increases linearly with pressure. Without making any assumption on the interconnection between the scaling exponent and the Gruneisen parameter, we prove that the scaling exponent is identical with the pressure derivative of the isothermal bulk modulus. We further discuss probable interconnection between the scaling exponent and the Gruneisen parameter.meter.