Advancing the thermodynamic modeling of multicomponent phases in hydrogen-para-equilibrium

Abstract

We present an advanced approach for the thermodynamic modeling of metal hydrides within the Calculation of Phase Diagrams (CALPHAD) framework. As the traditional CALPHAD method requires significant and time-consuming manual input, often introducing biases into the assessment process, we present a novel solution to automate this. The core of our approach is the development of an open-source, Python-based computational tool designed to calculate para-equilibrium states in hydrogen-multicomponent phases. This tool facilitates a semi-automatic pathway to enhance the CALPHAD evaluation procedure, significantly reducing manual input. We validated our approach by rapidly assessing the (Ce,La)Ni₅–H system, a representative material system with significant implications for metal hydride-based hydrogen applications. Our method confirms existing data and reveals new insights into this system’s sorption properties and phase behavior. Using our Python-based tool to optimize parameter sets and calculate Pressure-Composition-Isotherms (PCI), we demonstrate the feasibility of predicting temperature-dependent plateau pressures and hydrogen capacities of multicomponent metal hydrides. This work holds significant potential for future applications in designing hydrogen storage materials, predicting their properties, and extending the methodology to other metal hydride systems.