Theoretical investigation of the thermodynamic stability of nano-scale systems-II: Relaxation of a junction profile

Nonlinear relaxation of a sharp density profile typical of layered semiconductor junctions is studied using an irreversible statistical mechanical technique, the Path Probability Method, taking into account nearest neighbor correlations. The vacancy mechanism and the pair approximation are used. It is found that atoms near a sharp density profile diffuse up against the density gradient. Our numerical examples demonstrate that in this range there is a possibility that the atom flux can go either down along or up against the local chemical potential (μ) gradient. However, the calculations do not deny the possibility of modifying the definition of μ in such a way that the atoms always flow toward the direction of decreasing μ.