Novel High Pressure Structures of Polymeric Nitrogen

The search for the stable monatomic forms of solid nitrogen is of great importance in view of its potential application as a high-energy-density material. Based on the results of evolutionary structure searches, we proposed two high-pressure polymeric structures to be stable beyond the stability field of the synthesized cubic gauche structure-the layered Pba2 or Iba2 (188-320 GPa) and the helical tunnel P2(1)2(1)2(1) structure (> 320 GPa). We rule out the low-temperature stability of the earlier proposed black phosphorus structure. Stability fields of the newly predicted polymorphs are within the reach of current experimental techniques.