Meyer-Neldel rule for the kinetic properties of grain and interphase boundaries

The Meyer-Neldel rule (MNR) or compensation effect is observed in wide range of phenomena. MNR appears to be a fundamental property of many families of activated processes following an Arrhenius dependence on temperature. The kinetic properties of grain boundaries (GBs) and interphase boundaries (IBs) in solids depend strongly on their crystallographic parameters and obey the Arrhenius law. Therefore, the GBs form the families of objects where the Meyer-Neldel behaviour of thermally activated processes can be easily observed. The data on MNR for GBs in At, Zn and Sn, GB triple joints in At and Zn, and Sn-Ge IBs are presented. The data on "pressure NMR" for Sn tilt GBs and Ge-Sn twist IBs are presented as well. The thermodynamic model describing the activated state for GB diffusion and migration as a heterophase fluctuation is discussed. The values of compensation temperature for GB and IB diffusion and migration and GB triple joint migration are discussed using the idea of heterophase fluctuations.