Vacancy concentrations in metals in equilibrium with H2-gas at high pressures

The effect of equilibrium vacancy formation on the solubility of hydrogen in metals has been derived. The treatment is based on a Fermi–Dirac distribution function so that problems which arise at low temperatures in Maxwell–Boltzmann formulations are obviated. Using input data for Ni, the effect of vacancy formation on the validity of Sievertsʹ law is calculated and the (pT)-region in which the thermodynamic functions of the solute (H) atoms can be easily extracted from measured solubility has been mapped.