The Molecular Diffusion options are organized under the tabs Constituent Materials, Solver Options, and Equations & References.

Constituent Materials

As described for the Bulk (Laplace) Diffusion, the user sets which material ID corresponds to pore space and which material IDs denote solids under the Constituent Materials tab.

Be aware that the choice of fluid does not influence the results. The relevant parameters describing the fluid are the Mean Free Path Length and the Mean Thermal Velocity.

Solver Options

The solver options are identical to those of the Knudsen Diffusion command solver options.

Equations & References

The Equations tab shows the relevant equations for illustration and explains the used variables and constants.