Hydrogen solution in nonequimolar CrMoNbV high-entropy alloys

With the growing importance of hydrogen (H) as a future clean energy source, high-entropy alloy (HEA) materials have attracted increasing attention in the areas of H storage, transport, and embrittlement resistance. The great tailorability of elemental composition in HEAs holds the promise of an unprecedented potential for tuning H solubility, diffusivity, and trapping with a target property. In this study, we formulate CrMoNbV HEAs by mixing elements with a high and low H affinity and calculate the H solution energy at all the 768 distinct tetrahedral interstitial sites that are available in a 128-atom unit cell via density functional theory, thereby obtaining the full energy landscapes of H interstitials for 12 different elemental compositions. The results are systematically analyzed from the perspective of the relationship between global and local composition with respect to the H solution energy. A significant influence of the composition on the H solution energy landscape is observed, predicting that the mean H solution energy is tunable by ``global'' composition while the energy variance is affected by the residual strain of the HEAs caused by different atomic sizes. Large fluctuations in the H solution energy over the same ``local'' composition are observed, which suggests that the prediction of H solution energy solely in terms of local atomic descriptors requires a cautious approach. We also show that among all the constituent elements, the Mo content has a notable impact on tuning the distribution of H solution energy with a wide range of the mean and variance.