High-pressure stable phases in mercury azide

Exploring the bonding properties and polymerization mechanism of the polymer phases of nitrogen-rich compounds is one of the goals of high-pressure research. Considering first-principles calculations, a particle swarm optimization structure search method has been used to study the structural evolution behavior of nitrogen in HgN3 up to 200 GPa. Three new phases with P-1, P2(1)/m, and P-1 structures at pressures of 38 GPa, 125 GPa, and 148 GPa are identified for the first time. The theoretical calculations show that the two P-1 structures are dynamically stable at 50 GPa and 200 GPa. In these two phases, the nitrogen atoms form an infinite one-dimensional zigzag chain and connected N-6 ring, respectively. Two stable structures have semiconductor properties throughout the stable pressure range, primarily due to sp(2) hybridization of nitrogen atoms. Our studies provide a theoretical basis for the synthesis of polymeric nitrogen in high-pressure experiments and indicate the direction for future studies of mercury azide.