Stabilized N5 and N6 rings in the Ag–N system under modest pressure

High pressure enables the creation of novel functional materials by modifying chemical bonding and crystal structure, opening avenues for the development of high-energy-density polynitrogen materials. We present the high-pressure synthesis of three polynitrides P1 AgN7, P21/c AgN5, and P-1 AgN4, achieved through direct reactions between silver and nitrogen. Notably, the synthesis pressures required for the formation of N5 and N6 rings from metal–nitrogen reactions in this work represent the lowest values reported to date in high-pressure studies. At 15 GPa, isolated N5 rings are stabilized in P1 AgN7 and P21/c AgN5. At 26.3 GPa, P-1 AgN4 is synthesized, featuring infinite one-dimensional nitrogen chains composed of alternating N2 and N6 rings, a unique catenation not observed in other polynitrides. In addition, AgN7, AgN5, and AgN4 possess significantly higher volumetric energy densities Ev than the conventional explosive TNT, making them promising high-energy-density materials.