Superhardness, stability, and metallicity of diamondlike BC5: Density functional calculations

The recently synthesized diamondlike BC5 (d-BC5) was shown to own a few interesting physical properties, which are yet to be confirmed due to the difficulty in the synthesis of adequately sized single crystals. Our density functional calculations not only confirm d-BC5 to be an ultraincompressible and superhard material, but also reveal that it exhibits mechanical stability and metallic behavior. The higher energy barrier of d-BC5 (0.057 eV/atom higher than diamond) implies that d-BC5 is about 500 K more kinetically stable than diamond. Moreover, the trend that the mechanical properties drop with the increasing of boron content in diamondlike B-C compounds (d-BCx) can be understood through analyzing the electronic structures. The combination of high hardness, strong stiffness, large activation barrier, and metallic feature allows this series of d-BCx promising applications as advanced abrasives and electronic devices at high temperature and high-pressure conditions.