Modelling of phase equilibria in metal-hydrogen systems

The paper presents a model quantitatively describing phase equilibria in metal-hydrogen systems. It is based on a formal consideration of interstitial hydrogen dissolved in the metal matrix as a van der Waals lattice gas. The model describes the asymmetry of the experimental 'pressure-composition' isotherms. It postulates an existence of local fluctuations in the stoichiometric composition of the alloys, causing an appearance of statistical deviations of the correlated values of entropy and enthalpy from their corresponding mean values. The model describes temperature-dependent plateau slopes and smooth transitions between alpha-, (alpha+beta)- and beta-regions. It was applied in the approximations of both single (LaNi4.8Sn0.2-H-2) and double plateau (TiCr1.9-H-2) experimental PCT-diagrams. (C) 2003 Elsevier B.V. All rights reserved.