An electrochemomechanical theory of defects in ionic solids. I. Theory

Abstract

Charged defects diffuse through an ionic solid under electrochemical driving forces. Such a diffusion process can be affected by mechanical stresses in the solid. A deviation of defect concentration from its stoichiometric value during diffusion can cause volumetric strains in the solid. Such strains will result in mechanical stresses if the ionic solid is under mechanical constraint, or if the defect distribution is non-uniform. We develop a framework to account for the coupling between mechanical stresses and diffusion of charged defects in ionic solids. The framework consists of a system of nonlinear differential/algebraic equations governing the defect concentrations, electrostatic potential and the mechanical stresses. It is believed that this framework is the first fully coupled theory for the interaction between mechanical stresses and electrochemical forces in ionic solids.

Acknowledgements

The authors would like to express their gratitude to Professor Meilin Liu of Georgia Tech as an invaluable source of knowledge on electrochemistry. His help is greatly appreciated. The work was partially supported by the US Department of Energy under contract No. DE-AC26-02NT41571. JQ was also supported in part by NSFC through Grant 10228204. YS was supported in part by NSFC through Grant 10472028 and the Fund of Excellent Youth of Heilongjiang Province.