Papers by Keyword: Activation Entropy

Abstract: Solute drag theory is critically revisited and an alternative approach is presented to account for the effect of solute elements on grain boundary migration during annealing. A fundamental new concept is introduced in the model that, in the linear range of irreversible thermodynamics, solute atoms segregated in a grain boundary will not lag behind when the boundary migrates. While lagging behind is the very essential assumption for the solute drag theory. Instead of blaming the lagging behind, the mobility drop due to solute addition is attributed to the decrease in boundary energy as a result of boundary segregation. According to this model, grain boundary mobility is dependent on solute concentration rather than migration rate. The predictions of the model are compared with experimental results, with a good agreement.

Abstract: The first part of this paper presents a brief historical account of the Arrhenius law, starting from the seminal paper by Arrhenius (1889) up to theoretical developments mainly based on the rate theory. The second part describes the so called compensation rule (Meyer-Neldel rule), a correlation between activation enthalpy and entropy (or between pre-exponential factor and activation energy) , and discusses whether this correlation is trivial or bears some physical meaning.