ExploringNH𝑥−Xecompounds with high hydrogen storage capacity and stability at high pressure

Recent studies have demonstrated that the chemical reactivity of noble gas elements, such as Xe and He, increases significantly under high pressure, leading to the discovery of many unconventional compounds that are unstable under ambient conditions. In this paper, we propose three different and energetically stable compounds—NH5⁢Xe, NH11⁢Xe, and NH13⁢Xe—through a combination of structural prediction methods and first-principles calculations. Our findings reveal that these compounds are dynamically stable and possess wide band gaps exceeding 4 eV, classifying them as insulators. Notably, the incorporation of xenon enhances the hydrogen content within the compounds, with NH11⁢Xe and NH13⁢Xe exhibiting the highest hydrogen storage capacities among the proposed compounds, reaching up to 44% and 48%, respectively. This positions them as promising candidates for advanced hydrogen storage materials. Furthermore, ab initio molecular dynamics simulations reveal that these compounds undergo phase transitions from solid to superionic and eventually to liquid as temperature increases. The stable pressure-temperature regions of the superionic and liquid phases align with the extreme conditions found in the interiors of Earth and icy planets (Uranus and Neptune), suggesting that these NH𝑥−Xe compounds could be potential constituents of their mantles. These results not only provide the potential of NH𝑥−Xe compounds in hydrogen storage but also offer distinct insights into the composition and behavior of materials under extreme conditions in planetary interiors.