First-principles study of the surface structure and stability of BC5

BC5 with both superhard and superconducting properties is expected to have important applications in many fields. In this work, the low-index surface structures and properties of BC5 have been identified by first-principles calculations. The surface stability decreased in the order of (011) > (010) > (101) > (100) > (110) > (111) > (001). The (011), (101), and (110) surfaces exhibit the strongest surface relaxation, followed by (111), and the (001) surface is the least. A DFT (density functional theory)-based Wulff construction of the equilibrium shape of BC5 shows that the surface with the largest exposure area is (011), followed by the (101) and (001) surfaces. Electronic analyses show that Pmma phase BC5 and all considered low-index surfaces exhibit metallic character where the surfaces are even stronger. Larger charge redistribution in the low-index surfaces is found compared with the bulk case.