ABSTRACT Interactions between simple diatomic molecules such as N 2 and O 2 under high pressure can produce complex solid solutions, novel alloys, and modified chemical reactivity. Despite its importance, the structural evolution and lattice dynamics of the oxygen‐rich N 2 /O 2 system at pressures above 12 GPa remain poorly understood. Here, we investigate compositions with 78, 88, and 95 mol% O 2 using in situ Raman spectroscopy in diamond anvil cells over a pressure range of 0–49 GPa, with comparison with pure N 2 and O 2 . In the 6–20‐GPa range, increasing oxygen content shifts the nitrogen Raman mode to higher wavenumbers, reflecting enhanced compression and bond stiffening of N≡N, likely due to oxygen‐induced modified local intermolecular interactions and lattice compression. Above approximately 20 GPa, oxygen extensively substitutes into the nitrogen lattice, and the system stabilizes in a C 2 /m structure analogous to high‐pressure pure oxygen (up to 49 GPa), indicating oxygen‐dominated lattice control. For the supersaturated system (O 2 above 95 mol%), coexisting alloy (95 mol% O 2 ) and mixture (96 mol% O 2 ) domains emerge, in which oxygen polymerization is influenced by weak van der Waals interactions with N 2 (~1.79 kJ/mol near 10 GPa). These findings provide a unified framework for understanding the structural and vibrational behavior of oxygen‐rich binaries under extreme pressure, with implications for planetary interiors and the synthesis of novel materials.
Zhao et al. (Fri,) studied this question.