Structural and Electronic Competing Mechanisms in the Formation of Amorphous Carbon Nitride by Compressing s-Triazine

The pressure-induced transformation of molecular crystals can give rise to new materials characterized by intriguing hardness or energetic properties. Mechanisms regulating these reactions at the molecular level result from a complex interplay among crystal structure, lattice dynamics, and electronic properties. Here, we show that the formation of a three-dimensional amorphous carbon nitride by compressing phase II s-triazine is controlled by the competition between two different mechanisms, one entirely structural and the other electronic, representing the first example where such occurrence is demonstrated. Temperature drives the reactivity below 8 GPa by ruling the lattice dynamics, whereas above 8 GPa the electronic modifications, uniquely governed by pressure, trigger the chemical transformation. The amorphous material synthesized has a bonding structure characterized by a bulk typical of a strongly conjugated three-dimensional carbon nitride with hydrogen atoms migrated to saturate C and N terminations.