Isotope Effects in the Diffusion and Solubility of Hydrogen in Nickel

Abstract

The solubility and diffusivity of hydrogen and deuterium in a single crystal of nickel have been measured in the range 490°—690°K. The theory of isotope effects has been developed in the harmonic approximation. It is shown that the experimental results can be quantitatively accounted for in terms of the derived expressions. The theory is tested by calculation of the pre‐exponential factor for diffusion (D₀) using only the data for the relative diffusivities of hydrogen and deuterium. The calculated value is in excellent agreement with experiment if it is assumed that direct jumps of hydrogen from one octahedral site to another are involved.