Diffusion can take place through the interstitialcy mechanism, also known as the indirect interstitial mechanism, when an interstitial atom has approximately the same size as the lattice atoms or the lattice atoms within a specific sublattice of a compound. In this mechanism, a (self) interstitial atom replaces an atom located at a substitutional site, which in turn displaces a neighboring lattice atom, as illustrated in Figure . It is worth noting that non-collinear variations of the interstitialcy mechanism, where atoms move at an angle to each other, can also occur. These mechanisms are considered collective mechanisms because they involve the simultaneous movement of at least two atoms.