  The lighter group-V element phosphorus forms the As-type (hR2) structure
under pressure, above 5 GPa, and at 10 GPa transforms to the simple cubic
structure (cP1), similar to arsenic. Despite of its low packing density, the
simple cubic structure is stable in phosphorus over a very wide pressure range
up to 103 GPa. On further pressure increase, the simple cubic structure
transforms to a simple hexagonal structure (hP1) via a complex phase that was
solved recently as incommensurately modulated. Structural transformations of
phosphorus are connected with the changes of physical properties. Above 5 GPa
phosphorus shows superconductivity with Tc reaching ~9.5K at 32GPa. The crystal
structures and properties of high-pressure phases for phosphorus are discussed
within the model of the Fermi sphere and Brillouin zone interactions.
