The Thermodynamics And The Firsts Principle Calculations For The Process Of LaNi₅'s Storage Hydrogen

Intermetallic compounds are widely applied to the storage and transportation of hydrogen for their superior qualities. LaNi₅ alloy is one of excellent hydrogen- storage materials for its high-density of hydrogen-storage, moderate equilibrium pressure, activability, rapidness and reversibility for the absorption and desorption of hydrogen. At present, many experimental and theoretical studies on LaNi₅ and its derivatives have been done, but it is still important and difficult to explain the process of hydrogen storage process quantificationally. In this paper the thermodynamics equilibrium for the process of LaNi₅'s hydrogen storage is derived theoretically. The thermodynamics functions of LaNi₅ and its hydrides are calculated based on the first-principle method. The results are as follows:(1) The thermodynamic equilibrium for the process of LaNi₅ alloy's hydrogen storage is analyzed; An equilibrium formula describing the relationship of the equilibrium pressure-content-temperature (p-c-T) for covering all the available experimental data has been derived from the thermodynamics functions.(2) The experimental data of the process of LaNis'₅ hydrogen storage are fitted with the equilibrium formula. The experimental p-c-T relationship is are represented. The thermodynamic functions such asâ–³H₁,â–³S₁, andâ–³G₁ for the process of the hydrogen storage are derived and discussed. The results indicate the thermodynamics functions for the equilibrium are dependent upon the temperature and essentially independent upon the equilibrium pressure.(3) The energies, volume moduli and thermodynamics functions of LaNi₅ and its hydrides LaNi₅H_n (n = 1, 2, 3, 4, 5) based on the first principle method are optimized and calculated. The parameters of p-c-T relationship are calculated and compared with those fitted from the experimental data.