Raman studies of black phosphorus from 0.25 to 7.7 GPa at 15 K

Raman scattering experiments from a polycrystalline sample of black phosphorus were done with a diamond-anvil cell from 0.25 to 11.6 GPa at a temperature of 15 K. Three Raman-active modes in the A11 orthorhombic (Cmca) phase were observed as a function of pressure to approximately 7.7 GPa, the point where black phosphorus has fully transformed to the rhombohedral (R3{}m) structure. No Raman scattering was observed above 7.7 GPa. The frequency shifts with pressure at 15 K are approximately half those found at room temperature by previous workers.