Structural stability and equation of state of simple-hexagonal phosphorus to 280 GPa: Phase transition at 262 GPa

A structural phase transition and the equation of state of the simple-hexagonal (sh) phase, P-V, of phosphorus were investigated at pressures up to 280 GPa using monochromatic synchrotron x-ray diffraction. The P-V phase, which was stable above 137 GPa, has shown a structural transition to a higher-pressure phase, P-VI, above 262 GPa, while the $c/a$ ratio of the sh phase slightly increased with increasing pressure from 0.948 to 0.956. The structure of the P-VI phase has been proposed to be bcc. The bulk modulus (B₀) and the atomic volume at atmospheric pressure (V₀) of the sh phase were estimated to be 84.1 GPa and 14.2 ³, with a fixed value of the pressure derivative of the bulk modulus (B₀^').