High-Pressure Synthesis of K₄N₆ with All Nitrogen Atoms Forming Aromatic Hexazine [N₆]^4- Anions

Realizing compounds entirely composed of aromatic hexazine N₆ rings with high stability is a long-term challenge. Existing high-pressure synthesized compounds contain a maximum of 5.36% N atoms, forming aromatic [N₆]^4- rings. We predict that all N atoms contribute to aromatic [N₆]^4- rings in K₄N₆, which become stable at 60 GPa and can stably exist up to 600 K at 0 GPa. Furthermore, K and KN₃ are suggested as precursors for the synthesis of K₄N₆. Following this approach, based on the diamond anvil cell, K₄N₆ with 100% nitrogen atoms forming aromatic hexazine [N₆]^4- rings is synthesized at 45 GPa after laser heating and identified by synchrotron X-ray diffraction and Raman spectroscopy. Our results bring us closer to achieving aromatic N₆ rings at ambient condition.