Existence of solid Na–Xe compounds at the extreme conditions of Earth's interior

Previous studies have suggested that high pressure may induce chemical activity in noble gases (He and Xe), resulting in the emergence of high-pressure compounds containing these elements. By using first-principles theory and crystal structural prediction methods, we propose that six unconventional stoichiometries, namely, ${\mathrm{Na}}_{2}\mathrm{Xe}$, NaXe, ${\mathrm{Na}}_{2}{\mathrm{Xe}}_{3}, {\mathrm{NaXe}}_{2}, {\mathrm{NaXe}}_{3}$, and ${\mathrm{NaXe}}_{4}$, can be stabilized at pressures ranging from 48 to 400 GPa, which is the highest pressure considered in this study. All the predicted Xe-containing compounds exhibit metallic properties with strong ionic Na--Xe bonds. Further $ab\phantom{\rule{3.33333pt}{0ex}}initio$ molecular dynamics simulations show that NaXe, ${\mathrm{NaXe}}_{3}$, and ${\mathrm{NaXe}}_{4}$ remain in the solid state under extreme conditions, such as those present in the Earth's mantle, at pressures up to 135 GPa and temperatures up to 5000 K. This suggests that Na--Xe compounds might be possible constituents inside the Earth's mantle. These findings not only enhance our understanding of the Earth's interior, but also provide insights into Xe chemistry.