# Effective diffusion coefficient of a species in a heterogeneous mixture

I want to calculate the effective diffusion coefficient of hydrogen radical in a mixed-phase consisting of metal oxide, metal hydride and metal. I consider the interfaces to be diffuse.

How can I calculate the effective diffusivity or effective diffusion coefficient of a species (ion or radical) in a heterogeneous mixture consisting of 3 different components? Can I weight average the diffusivities or is it more complicated than that?

• I’m general, with great difficulty. – Jon Custer Oct 18 '18 at 14:42

$$\frac{\mathrm dn}{\mathrm dt} = \frac{A \times \nabla C}{\sum\frac{L_i}{D_i}}$$