Bipentazole (N 10 ): A Low-Energy MolecularNitrogen Allotrope with High Intrinsic Stability

In this letter, we report a crystal structure prediction and characterization of a molecular nitrogen allotrope N10 (bipentazole) using state-of-the-art computational methods. To date, in the form of a P21 space group crystal, this allotrope is the most stable predicted form of nitrogen, other than N2, in the pressure range 0-42 GPa. Its metastability at ambient conditions was justified using phonon dispersion and mechanical properties calculations as well as ab initio molecular dynamics simulations. Due to a high intrinsic stability caused by aromaticity, bipentazole may appear to be the first nitrogen allotrope being stable enough for a large-scale synthesis at ambient conditions. The calculations of propulsive characteristics revealed that bipentazole is an excellent "green" energetic material. A potential strategy for the synthesis of this compound is offered and rationalized. The unique electronic structure of bipentazole makes it a strongly electrophilic all-nitrogen reagent, which can exhibit unusual chemistry.