%A Yiming Zhang, Shuyi Lin, Min Zou, Meixu Liu, Meiling Xu, Pengfei Shen, Jian Hao, and Yinwei Li %T Prediction of Superhard BN$_{2}$ with High Energy Density %0 Journal Article %D 2021 %J Chin. Phys. Lett. %R 10.1088/0256-307X/38/1/018101 %P 018101%V 38 %N 1 %U {https://cpl.iphy.ac.cn/CN/abstract/article_105827.shtml} %8 2020-11-16 %X Considering that pressure-induced formation of short, strong covalent bonds in light-element compounds can produce superhard materials, we employ structure searching and first-principles calculations to predict a new class of boron nitrides with a stoichiometry of BN$_{2}$, which are stable relative to alpha-B and alpha-N$_{2}$ at ambient pressure. At ambient pressure, the most stable phase has a layered structure (h-BN$_{2}$) containing hexagonal BN layers between which there are intercalated N$_{2}$ molecules. At 25 GPa, a three-dimensional $P4_{2}/mmc$ structure with single N–N bonds becomes the most stable. Dynamical, thermal, and mechanical stability calculations reveal that this structure can be recovered under ambient conditions. Its calculated stress-strain relations demonstrate an intrinsic superhard nature with an estimated Vickers hardness of $\sim$43 GPa. This structure has a potentially high energy density of $\sim$4.19 kJ/g.