Tracer diffusion coefficients of polar systems

A new model for tracer diffusion coefficients of real systems containing at least one polar component (solvent and/or solute) is proposed in this work. It is applicable for dense gas, liquid, and supercritical phases. It is based on the Rice and Gray approach applied to the Stockmayer potential. The new expression embodies three friction coefficients to take into account a repulsive hard sphere core, a soft Lennard–Jones contribution, and a specifically polar interaction term. The model is explicit on temperature and density, and requires only two parameters. The validation was accomplished with the largest database ever compiled – 211 binary systems and 3463 data points – giving rise to an average absolute relative deviation (AARD) of 3.65%. In the particular case of systems with polar solvents – the main objective of this essay – very accurate results were also obtained: AARD=4.27% for 141 systems and 1994 experimental points. The predictive capability of the new model was also evaluated, exhibiting good and reliable behavior. A spreadsheet for D12 calculation is provided.

► New model for tracer diffusivities of polar systems is presented.
► The largest tracer diffusion coefficients database was compiled in this work.
► Model provides very small deviations for polar systems (4.27% and 2.80%).
► The new model exhibits reliable predictive capability.