Molecular crystals as precursors for poly-nitrogen

The application of pressure to matter results in dramatic modifications of its properties. The compression of molecular crystals first eliminates ``empty'' space between the molecules. It then alters the electron density distribution, favoring the increase of atomic coordination and the formation of polymers. The polymerization of low-Z compounds into covalently-bonded networks in three dimensions tend to generate materials characterized by superconductivity, super-hardness, and high-energy density.$^{\mathrm{1}}$ Poly-nitrogen (analogous to diamond) has been synthesized under extreme conditions above 100 GPa and 2000 K in diamond anvil cells, but could not be recovered to ambient conditions.$^{\mathrm{2}}$ A useful form of poly-nitrogen would have to be synthesized at low-pressure with enhanced stability at ambient conditions. The changes in the intermolecular and intramolecular interactions with pressure play a crucial role in the synthesizing and stabilizing of the structure as well as in tuning its properties. In this talk, we provide Raman and x-ray diffraction data on nitrogen-containing compound biuret and compare it to work on other possible poly-nitrogen precursors. References [1] W. Grochala \textit{et al.,} \textit{Angew. Chem. Int. Ed.} \textbf{46, }3620 (2007). [2] M. I. Eremets \textit{et al.}, \textit{Nat. Mater. }\textbf{3,} 558 (2004).