Chin. Phys. Lett.  2021, Vol. 38 Issue (1): 018101    DOI: 10.1088/0256-307X/38/1/018101
 CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY |
Prediction of Superhard BN$_{2}$ with High Energy Density
Yiming Zhang1†, Shuyi Lin1†, Min Zou1, Meixu Liu1, Meiling Xu1*, Pengfei Shen2, Jian Hao1*, and Yinwei Li1
1Laboratory of Quantum Functional Materials Design and Application, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116, China
2Academy for Advanced Interdisciplinary Studies, Southern University of Science and Technology, Shenzhen 518055, China
 Abstract 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. Received: 07 October 2020      Published: 06 January 2021 Fund: Supported by the National Natural Science Foundation of China (Grant Nos. 12074154, 11904142 and 11722433), the Science and Technology Project of Xuzhou (Grant No. KC19010), the Six Talent Peaks Project and the 333 High-Level Talents Project of Jiangsu Province, and the Natural Science Research Projects of Colleges and Universities in Jiangsu Province (Grant No. 19KJB140001).