Self-diffusivity is the same as diffusivity of individual species.
There are two types of diffusivities:
Self-diffusivity (also called Intra-diffusivity): In this type of diffusivity there is not macroscopic mixing . It can be described as the migration of individual species within a bulk solution, without changes in the concentration of the bulk solution. This type of diffusivity is mostly used when reactions occur at an interface.
Mutual diffusivity (also called inter-diffusivity): In this type of diffusivity there is macroscopic mixing, and there is diffusion between two or more solutions. This type of diffusivity occurs in mixing situations such as crystallization process.
You can also find more information about how OLI models self-diffusivities in the AQ and MSE frameworks.
- AQ framework: A. Anderko, M. Lencka. Ind. Eng, Chem. Res. 1998, 37, 2878-2888
- MSE framework: P. Wang, A. Anderko. Ind. Eng. Chem. Res. 2003, 42, 3495-3504