ENTHALPY AND ENTROPY CHANGES FOR NONSTOICHIOMETRIC HYDRIDE FORMATION

The general problem of the interpretation of thermodynamic data derived from plots of In p 1 2H (two phase) versus T-1 is considered in detail for solid-H systems. The often observed linearity of such plots over wide temperature ranges is examined using a series of approximations. It is shown that linear plots must result for solid-H systems where the dissolved H can be described by a mean field-lattice gas model (regular interstitial solution model). Model solid-H systems are considered where linearity in the In p 1 2H (two phase) versus T-1 plots is not expected. The approximations developed for the two-phase thermodynamic parameters are applied to the real systems PdH and NbH. © 1979.