Physics:Self-diffusion

According to IUPAC definition, self-diffusion coefficient is the diffusion coefficient $D_i^{*}$ of species $i$ when the chemical potential gradient equals zero. It is linked to the diffusion coefficient $D_i$ by the equation: $D_i^{*}=D_i\frac{\partial \ln c_i}{\partial \ln a_i}.$

Here, $a_i$ is the activity of the species $i$ in the solution and $c_i$ is the concentration of $i$. 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