THERMODYNAMIC EQUILIBRIA IN 2-PHASE, ELASTICALLY STRESSED IONIC-CRYSTALS

The conditions for thermodynamic equilibrium in two-phase, multicomponent, elastically stressed ionic crystals are derived within the realm of phenomenological thermodynamics using a Gibbsian variational approach. Equilibria between a stressed ionic crystal and a fluid and between two elastically stressed crystals possessing a coherent interface are examined, and an expression for the dependence of the electrochemical potential on stress is derived. The equilibrium conditions are used to calculate composition changes in a ternary (Mg,Ni)O film and the corresponding change in the thermodynamic stability of the film owing to substrate-induced stress. In this example, a substrate-induced strain of 1% yields an absolute shift in composition of 1.1 at.% at 1000 K. Significantly smaller or larger shifts are possible depending upon material parameters.