“…Experimentally, it is well-known that pressure favors the formation of nitrogen-rich materials, helping to overcome the energy barrier due to lone pair repulsion, as demonstrated by the employment of high pressure techniques in the synthesis of nitrides. − Some unsuccessful attempts to reduce the extreme pressure and temperature conditions for the synthesis of cg-N have been performed by using metallic catalysts or the azide ion as starting material instead of molecular nitrogen . On the other side, many computational studies searching for a convenient approach to reduce the instability of polynitrogen materials have reported the insertion of different heteroatoms (oxygen, , phosphorus, and carbon) into the polynitrogen framework to be efficient in relieving chain or ring strain in the case of several isolated molecular systems with different linear or cage , geometries, increasing both their thermodynamic and kinetic stability. In particular it has been found that for linear N x C 2 molecules the energy release properties vary linearly with the chain length and that the chains exhibit a good resistance to dissociation when terminated on both sides by CN groups .…”