科研之友
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摘要
Three novel boron nitrides (alpha-, beta- and gamma-BN) have been proposed as the candidates of BN family. By means of density functional theory (DFT) calculations, we find the three BN polymorphs exhibit high elastic properties and Vickers hardness which is even better than some metal nitrides and carbides. The alpha-BN and beta-BN are both mechanical and dynamically stable at zero pressure. But the gamma-BN is dynamically unstable due to soft mode occurring in phonon dispersion relations and can only exists under high pressure. Accurate hybrid functional calculations show that the alpha-BN is an insulator and the beta-BN is a wide bandgap semiconductor with the potential applications in optoelectronic devices. We predict the dynamically stable alpha-BN and beta-BN can be obtained by compressing (3, 3) BN nanotubes (BNNTs) over 8 GPa. Lower transition barriers also show the feasibility to synthesize the alpha-BN and beta-BN by high pressure methods. In addition, the special structure of beta-BN implies it can be used as a precursor to obtain a multiporous BN by pulling (A) over bar (3, 3) BNNTs out from the beta-BN.
- 出版日期2015-12
- 单位南昌大学
