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

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.