Parameters of the vacancy formation and self-diffusion in the iron

Abstract

The parameters of the electroneutral vacancy formation and self-diffusion of atoms in iron have been calculated by the analytical method based on the paired four-parameter Mie–Lennard-Jones interatomic interaction potential. For the first time, all activation process parameters were calculated within the framework of a single method: Gibbs energy, enthalpy, entropy and volume for both the vacancy formation process and the self-diffusion process. The isobaric temperature dependences of the indicated activation parameters for bcc and fcc iron structures from T = 10 K–1810 K along two isobars: P = 0 and 10 GPa were calculated. It is shown that, at low temperatures, due to quantum regularities, activation parameters strongly depend on temperature, and the entropy of activation processes in this region is negative. In the high temperature region, a good agreement has been obtained with the experimental estimates of activation parameters for different iron structures known from the literature. It is shown that at the α-γ transition temperature (1184 K), the activation parameters decrease during the isobaric transition from the bcc to the fcc structure. At the γ-δ transition temperature (1667 K), the activation parameters increase during the isobaric transition from the fcc to the bcc structure. With increasing pressure, the jumps magnitude for the Gibbs energy and the enthalpy of the activation process increases, and for the entropy and volume of the activation process decreases.