High-pressure stable phases in mercury azide.

• Both zigzag nitrogen chain and connected N 6 ring have been found in HgN 3. • The two structures can be synthesized at a modest pressure. • Coulomb attraction and covalent interaction are found to stabilize the compounds. 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 HgN 3 up to 200 GPa. Three new phases with P- 1, P 2 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. [ABSTRACT FROM AUTHOR]