Theoretical study of hydrogen absorption and desorption in Ti1-xZrx Mn1.4 using statistical physics treatment: Microscopic investigation and thermodynamic potential interpretation

Experimental absorption and desorption isotherms of hydrogen in Ti1-xZrx Mn1.4 (x = 0, 0.1, 0.2, 0.3, 0.4) alloys at T = 293 K have been fitted using some theoretical model expressions treated by statistical physics through the grand canonical ensemble. The monolayer model with two types of sites is used to fit and interpret the experimental data. The physicochemical parameters governing the absorption-desorption processes and included into the model expressions could be numerically deduced from the relevant experimental isotherms. Six parameters of the model are fitted, namely the numbers of hydrogen atoms per site n1 and n2, the receptor site densities N1m and N2m, and the energetic parameters P1 and P2. The evolution of these parameters as function of composition x is plotted and explained in correlation with absorption-desorption processes. Finally, the thermo-dynamic potential functions which govern the sorption mechanisms such as internal energy Eint, free enthalpy of Gibbs Ga and entropy Sa were derived from statistical physics calculations based on the model adopted.