Computational Thermodynamic Design of Nb–Mo‐Based Refractory Multi‐Principal Element Alloy for Hydrogen Energy Storage

ABSTRACT

An integrated computational framework combining thermophysical parameter analysis, CALPHAD‐based thermodynamic modeling, and DFT‐informed thermodynamic pressure–composition–temperature (PCT) modeling was employed to accelerate the design of a refractory multi‐principal element alloy (RMPEA) for hydrogen storage. The alloy Al ₃ Nb ₆₀ Mo ₂₀ V ₁₆ Cr ₁ was identified as a promising candidate. Thermophysical parameters predicted the formation of a stable body‐centered cubic (BCC) solid solution with a density of 8.33 g·cm ⁻³ and a valence electron concentration of 5.15. CALPHAD simulations performed using Thermo‐Calc with the TCHEA4 database indicated that the equilibrium microstructure at room temperature is dominated by the BCC‐B2 phase (∼92 vol.%). PCT modeling further predicted dual‐plateau hydrogen absorption behavior, corresponding to sequential α→β and β→δ transformations, with a maximum theoretical hydrogen capacity of ∼2.34 wt.% H at 25°C. These results demonstrate that Nb–Mo‐based RMPEAs offer competitive hydrogen storage capacity combined with robust phase stability. More broadly, the study highlights the effectiveness of integrated computational thermodynamics as a predictive tool for the accelerated development of advanced hydrogen storage alloys. This approach enables rapid compositional screening, prediction of phase stability, and estimation of hydrogen storage behavior, thereby reducing reliance on extensive experimental trial‐and‐error.