Thermodynamic characterization and statistical thermodynamics of the TiCrMn-H-2(D-2) system

Pressure-composition (p-c) isotherms of the TiCrMn-H-2(D-2) system were mea sured over a wide temperature and pressure range (up to 1000 arm H-2/D-2) w hich included the super-critical range (above T-C). The macroscopic thermod ynamic parameters of the system and their isotope effects were evaluated. A lso, hysteresis phenomenon between absorption and desorption isotherms were obtained as a function of temperature for the two hydrogen isotopes. The e xperimental p-c isotherms were compared to model calculated ones derived by simplified statistical thermodynamic treatments. From this comparison micr oscopic energy-related parameters were evaluated. These parameters included the average hydrogen-lattice interaction, the pairwise nearest-neighbor hy drogen-hydrogen interaction and the average vibrational frequency of H(D) a t the interstitial sites. (C) 2000 Elsevier Science S.A. All rights reserve d.