Self-diffusion

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

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

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