Theoretical Methods of Hydrogen Diffusion Calculation in Metals Review

Abstract

In the review discuss some theoretical methods of hydrogen diffusion calculation in metals. True values of the energy barrier for hydrogen diffusion can be calculated from first principles. The transition from the theoretical values of the energy barrier to the model values of the activation energy is associated with considering additional influencing factors, primarily physical parameters – zero-point energy, decay of local deformation near the hydrogen atom, temperature-dependent potentials, etc. The presentation of the results is greatly influenced by the parameters of the diffusion models used for calculations - the Arrhenius equation, the Einstein formula of molecular dynamics, the Kerr diffusion equation, the operator expression of quantum statistical mechanics, and diffusion equation of statistical thermodynamics. The statistical model of H diffusion in FCC metals at a high temperature makes it possible to explain the high values of the pre-exponential factor of H diffusion coefficients. The results of many works show that quantum effects play a decisive role in the H diffusion in metals at low temperatures. Further development of quantum- mechanical theories of diffusion will allow for consideration of the influence of these factors.