Phosphorus, one of the Group V elements, has been known since 17 th century. Phosphorus crystallizes in a number of allotropic forms: white, red, violet, black, etc. Since 1980s the main interest has been attracted to the black phosphorus with orthorhombic (Cmca) structure (Fig. ) which was found to be the most stable allotrope. At room temperature and pressures up to 260 GPa black phosphorus exhibits a sequence of pressure-induced phase transitions: orthorhombic (Cmca)rhombohedral (R-3m) -simple cubic (Pm-3m) -simple hexagonal (P6/mmm) -bodycentered cubic . However, in spite of efforts devoted to high-pressure investigation of phosphorus at room temperature, there were only few high-pressure studies at high temperatures .