Self-diffusion

According to IUPAC definition,^[1] self-diffusion coefficient is the diffusion coefficient ${\displaystyle D_{i}^{*}}$ of chemical species ${\displaystyle i}$ when the chemical potential gradient equals zero. It is linked to the diffusion coefficient ${\displaystyle D_{i}}$ by the equation:

$${\displaystyle D_{i}^{*}=D_{i}{\frac {\partial \ln c_{i}}{\partial \ln a_{i}}}}$$

Here, ${\displaystyle a_{i}}$ is the activity of the species ${\displaystyle i}$ in the solution and ${\displaystyle c_{i}}$ is the concentration of ${\displaystyle i}$. This term is commonly assumed to be equal to the tracer diffusion determined by watching the movement of an isotope in the material of interest.

See also

• Brownian motion
• Diffusion
• Molecular diffusion

References

1. S. J. Chalk (1997). A. D. McNaught, A. Wilkinson (ed.). "IUPAC Compendium of Chemical Terminology 'The Gold Book'" (2 ed.). Blackwell Scientific Publications.