A microscopic study of absorption and desorption of hydrogen in LaNi4.85Al0.15 using the grand canonical ensemble of statistical physics

Abstract

Modeling of absorption and desorption isotherms of hydrogen on LaNi4.85Al0.15 alloy at 298 K, 303 K and 313 K has been achieved through the use of grand canonical ensemble in statistical physics. In fact, a monolayer model with two levels of energy has been adopted to better fit the experimental data. Besides, six physicochemical parameters have been used to better describe the absorption and desorption processes from the point of view of α and β phases. These parameters are divided into two types. The first type of parameters contains four main parameters, namely the number of atoms per site, nα and nβ, and the densities of hydrogen receptor sites Nmα as well as Nmβ. The second type of parameters are mainly the two energetic parameters Pα and Pβ which respectively refer to the pressures at half saturations for the α phase and the β phase. Thanks to these steric and energetic parameters, we could compare the absorption and desorption processes to highlight the evolution of these parameters during hysteresis encountered in the desorption isotherms.