Mechanism of the influence of hydrogen on the self-diffusion of nickel

The mechanism of influence of hydrogen on the self-diffusion of nickel is theoretically investigated in the quasifermionic approximation. We establish dependences of structural and energy parameters which characterize the processes of formation and migration of monovacancies on the hydrogen content of the metal. We also analyze the relative roles of the indirect electronic effect and hydrogen dilatation as factors promoting changes in the parameters of self-diffusion. It is shown that, in the presence of hydrogen, the energies of formation and migration of vacancies and the energy of activation of self-diffusion become lower. This explains the experimentally observed phenomenon of acceleration of the diffusion processes in nickel, other transient metals, and their alloys.