Method for predicting chemical compositions with desired hydrogen sorption pressures for multi-component compounds

A simple and powerful method for estimating compositions likely to meet a target hydrogen sorption pressure is introduced. This semi-empirical method is based on the ordinary least-squares method and is illustrated with AB 2 Laves phases. Based on this and on experimental P-c isotherms, an equation that links logarithm of the absorption fugacity to the chemical composition was determined for the Ti Cr x Cr Mn x Mn Fe 2 − x Cr − x Mn compounds at 10 °C: log f abs ( 10 ° C ) = − 1.70 x Cr − 0.727 x Mn + 3.61 ( f is the fugacity given in MPa and x Cr and x Mn are the Cr and Mn contents, respectively). In addition, we have demonstrated that this method is applicable not only for absorption but also for desorption fugacity over a wide temperature range. An estimation of the enthalpy and entropy of hydrogenation and dehydrogenation for a given AB 2 Laves phase of the Ti(Cr,Mn,Fe) 2 system is thus possible. Its hysteresis for a given temperature can also be deduced as well as the temperature at which the hysteresis becomes zero (i.e. T x ). Additional compounds were synthesized, and their hydrogen sorption pressures, enthalpy and entropy of reaction and T x proved close to expectations. Finally, this method can also be efficient for the prediction of other physical properties. This last point was demonstrated with the unit cell volume for ternary, quaternary and quinary compounds of the (Ti,Zr)(Cr,Mn,Fe) 2 system.