科研之友
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摘要
A new allotrope of nitrogen in which the atoms are connected to form a novel N-6 molecule is predicted to exist at ambient conditions. The N-6 molecule is a charge-transfer complex with an open-chain structure containing both single and triple bonds. The charge transfer induces ionic characteristics in the intermolecular interactions and leads to a much higher cohesive energy for the predicted crystal compared to solid N-2. The N-6 solid is also more stable than a previously reported polymeric solid of nitrogen. Because of the kinetic stability of the molecules and strong intermolecular interactions, the N-6 crystal is shown by metadynamics simulations to be dynamically stable around room temperature and to only dissociate to N-2 molecules above 700 K. The N-6 crystal can likely be synthesized under high-pressure high-temperature conditions, and the considerable metastability may allow for an ambient pressure recovery of the crystal. Because of the large energy difference between the single and triple bonds, the dissociation of the N-6 crystal is expected to release a large amount of energy, placing it among the most efficient energy materials known today.
