On predicting self-diffusion coefficients from viscosity in gases and liquids

The relations between self-diffusion and viscosity for compressed liquids and gases have been reviewed, and a new equation for correlating viscosities over wide ranges of temperature and pressure is proposed. This formula is inspired by the Lennard–Jones Chain model of Yu and Gao for self-diffusion, and represents the viscosities of 15 compounds (1046 data points) with an average absolute deviation of 6.95%. Moreover, as the presented equation and the Yu–Gao model require the same fitting parameters, the ability to calculate self-diffusion coefficients from the viscosity parameter is studied. Some of the classic reviewed relations, such as the Stokes–Einstein formula, are also contrasted with the available experimental data of both transport properties.