Thermal healing of defects in crystals Thermal treatment can heal point defects due to the diffusion of atoms towards empty points.
In a solid crystal structure, atoms do not diffuse at room temperature (correct?)
Energy of thermal treatment facilitate the solid-state diffusion. How the minimum energy for solid-state diffusion can be calculated?
 A: For calculations, one might use something like Density Functional Theory (DFT) to analyze the energetics of the stable defect states and the saddle points in between one site and another.  This can often be very complicated, particularly in semiconductors where the charge state of a defect impacts the energy and configuration. As an extreme case, you might look up the Borgoin-Corbett mechanism, where capture (or emission) of an electron leads to the defect shifting to a new stable configuration which turns out to be the saddle point for motion of the other charge state.  Then, emitting (or capturing) of an electrons can result in the defect dropping into an adjacent site.  This is a athermal diffusion event, having no activation barrier.
In general, though, you need to rethink your concept that atoms do not diffuse at room temperature.  While it may be true that atoms on lattice sites do not diffuse (much) at room temperature (unless near the melting point), that does not imply that defects (vacancies, interstitials, etc.) do not.  For example, in Si it is known that interstitials are mobile down to at least liquid He temperatures. Even the Si vacancy is fairly mobile at room temperature, as is well known in the radiation effects literature.
