Figure 1. Lattice and electronic structures of bulk black phosphorus.

(a) Crystal structure of bulk BP marked with coordinate axes (x, y, z), lattice vectors (a, b, c) and structural parameters (R1, R2, θ1 and θ2). (b) Brillouin zone path of BP primitive cell. (c) Electronic bandstructures for bulk BP calculated with the HSE06 functional (red solid line) and the mBJ potential (blue dashed line), together with fitted effective masses along the Z–T′–A′, Z–Q and Z–G directions. At the right of the image, a zoomed-in plot shows the direct bandgap at Z. E_VBM is the energy of valence-band maximum.