Hydrogen-sorption properties of magnesium and its intermetallics with Ca7Ge-Type structure

The statistical theory of the hydrogenation of magnesium and its alloys Mg₆M'M″(with M' = Mg, Ti, V, Nb, Zr; M″ = Mg, Al, Zn) has been developed. The energies of crystals have been calculated, and equations for their thermodynamic equilibrium state have been found. Equations for determining the P-T-c diagram have been obtained. Curves that determine the temperature dependences of the concentration of hydrogen desorbed from crystals were studied. The maximum hydrogen-desorption temperature and its dependence on interatomic-interaction energy parameters and the activity of hydrogen atoms were estimated. Isopleths of hydrogen solubility were calculated for different concentrations of hydrogen. The level of the curves for different coefficients of activity and slope for different hydrogen contents were found. Isotherms of hydrogen solubility in crystals were studied. The possibility of achieving the sorption hysteresis effect was clarified, and the length and width of the hysteresis loop at different temperatures were estimated. The aforementioned functional dependences were plotted. The calculated data were compared with experimental results available in the literature. The theoretical and experimental data agree qualitatively.