Synergistic DFT and HEAPS modelling of hydrogen adsorption energetics in high-entropy alloys: Ti0.25V0.25Cr0.25Mn0.187Al0.063

Abstract This study investigates the hydrogen adsorption energetics of the high-entropy alloy (HEA) Ti₀.₂₅V₀.₂₅Cr₀.₂₅Mn₀.₁₈₇Al₀.₀₆₃ using a synergistic computational approach combining density functional theory (DFT), High-Entropy Alloy Prediction Software (HEAPS), and pressure–composition–temperature (PCT) modeling. Thermodynamic descriptors obtained from HEAPS simulations predicted the formation of a stable body-centered cubic (BCC) structure, which was confirmed by Thermo-Calc equilibrium calculations as an ordered BCC_B2 phase. The thermodynamic stability of this phase arises primarily from favorable chemical ordering interactions (ΔH_mix = -6.45 kJ·mol⁻¹), supported by moderate configurational entropy (ΔS_mix = 12.7 J·mol⁻¹·K⁻¹) and a favorable valence electron concentration (VEC = 5.25). PCT simulations revealed a hydrogen storage capacity of approximately 3.99 wt% H, with characteristic solid-solution and hydride formation behaviors observed across different temperature ranges. Thermo-Calc analysis demonstrated a transition from low-temperature multiphase structures to a high-temperature stable BCC_B2 phase, confirming the thermal robustness of the alloy. DFT calculations revealed lattice expansion with increasing hydrogen content and negative heats of formation (-1.19 to -2.19 eV/atom), indicating energetically favorable and stable hydride formation. Electronic structure analysis showed strong hybridization between H-1s and Al-p orbitals, supporting the thermodynamic stability. These results demonstrate the strong potential of TiVCrMnAl-based HEAs as efficient hydrogen storage materials, with favorable structural stability, thermodynamic feasibility, and high hydrogen absorption capacity.