Hydrogen storage of high entropy alloy NbTiVZr and its effect on mechanical properties: A first-principles study

In recent years, high entropy alloys (HEAs) have demonstrated remarkable potential for hydrogen storage applications. Although extensive experimental studies have been conducted, a detailed understanding of the hydrogenation process at the atomic level is still lacking. In this study, first-principles calculations were employed to explore the microstructural evolution during hydrogen absorption in NbTiVZr as well as the mechanical characteristics of hydrides. The results indicate that a phase transition from BCC to FCC occurs in the hydride when the hydrogen content reaches 0.05 wt%. Hydrogen tends to occupy the octahedral interstitial sites in the BCC hydrides, while the preferred hydrogen sites in FCC hydrides undergo a transition from octahedral sites → tetrahedral + octahedra sites → tetrahedral sites as the hydrogen content increases. The highest hydrogen storage capacity of NbTiVZr was predicted by the phonon spectra of hydrides to be 2.94 wt%. Vanadium (V) is discovered to play a crucial role in hydrogen absorption capacity by causing significant lattice distortion and forming stronger bonds with hydrogen. Additionally, all hydrides exhibit great mechanical properties and thermal stability. Our research reveals that NbTiVZr has an excellent capacity for storing hydrogen and has the potential for applications in hydrogen storage materials.