Elongated Fermi surfaces in perovskites like SrTiO3 explain the T2 resistivity, previously thought to be from electron-electron interactions/scattering.
Why is chemical diffusivity similar to defect diffusivity, not self-diffusivity? How's tracer diffusivity related? Here's a guide to diffusion coefficients.
Using the generalized thermodynamic driving force, we find where the definition of diffusivity comes from.