Abstract
The pressure-induced transformation of diatomic nitrogen into nonmolecular polymeric phases may produce potentially useful high-energy-density materials. We combine first-principles calculations with structure searching to predict a new class of nitrogen-rich boron nitrides with a stoichiometry of that are stable or metastable relative to solid and -BN at ambient pressure. The most stable phase at ambient pressure has a layered structure () containing hexagonal layers sandwiched with intercalated freely rotating molecules. At 15 GPa, a three-dimensional structure with single N-N bonds becomes the most stable. This pressure is much lower than that required for triple-to-single bond transformation in pure solid nitrogen (110 GPa). More importantly, is metastable, and can be recovered under ambient conditions. Its energy density of makes it a potential high-energy-density material. In addition, stress-strain calculations estimate a Vicker’s hardness of . Structure searching reveals a new clathrate sodalitelike BN structure that is metastable under ambient conditions.
- Received 3 June 2015
DOI:https://doi.org/10.1103/PhysRevLett.115.105502
© 2015 American Physical Society