Investigation of the thermodynamic stability in phase separating thin films using the cluster variation method

The thermodynamic stability of the thin film of the fcc-based phase separating binary system is investigated using the pair approximation of the cluster variation method (CVM), which includes short-range order correlation. The concentration profiles through the lattice plane parallel to the free surface are calculated as a function of temperature and film thickness for both(100) and (111) thin films. It is observed that the thermodynamic stability of the thin film depends on the film thickness and orientation, and the critical temperature beyond which the thin film cannot phase separate decreases as the film thickness decreases. The calculated Warren-Cowley short-range order parameter shows that the (100) and (111) thin films have different segregation behavior at the surface and the interphase boundary.