According to density functional theory (DFT) calculations, phosphorene forms in a honeycomb lattice structure with notable nonplanarity in the shape of structural ridges. It is predicted that crystal structure of black phosphorus can be discriminated under high pressure. This is mostly due to the anisotropic compressibility of black phosphorus because of the asymmetrical crystal structures. Subsequently, the van der Waals bond can be greatly compressed in the z-direction. However, there is a great variation in compressibility across the orthogonal x-y plane.