A semi-phenomenological model was developed for large-angle random grain boundaries. The model was based upon the assumption that the boundaries had an island structure. The free volume of the boundary was taken to be a fundamental parameter that controlled the enthalpy and entropy of the boundary. Expressions were derived which gave the boundary free energy as a function of the boundary free volume, and of the crystallographic and thermodynamic parameters of the material.

V.N.Chuvildeev: Physics of Metals and Metallography, 1996, 81[2], 117-23