A thermodynamic approach to modeling multicomponent FeTi-based alloys for hydrogen storage

Abstract

Modeling the impact of alloying on the hydrogenation properties of intermetallic compounds is a vital yet challenging task for hydrogen storage materials design: not only do these processes occur under thermodynamic para-equilibrium conditions, but for bcc-derived compounds, the task is further complicated through varying composition-dependent ordering transitions. Here, we tackle these challenges by providing a multicomponent thermodynamic modeling framework for FeTi, a representative bcc-derived material class, which is one of the most relevant room-temperature interstitial metal hydrides. We aim specifically to describe para-equilibrium in FeTi-based multicomponent hydrides while ensuring compatibility with previously evaluated metallic systems. DFT point-defect calculations provide a physics-informed foundation to identify substitutional site preferences. Not only does our approach give detailed guidance for the selection of model parameters to evaluate phase equilibria for a broad range of FeTi-based multicomponent systems with high fidelity, but it also can be easily adopted to other interstitial hydrogen storage compounds.