RELATIVE STABILITY OF RED AND BLACK PHOSPHORUS AT P-LESS-THAN-1 GPA

Relative stability of red and black phosphorus at P < 1 GPa was investigated by rapid and slow cooling from the melt under high pressure and by baro-thermal analysis. The red form was produced from the melt of the black phosphorus. The density of the produced samples of red phosphorus was rho = 2.33 g cm-3. The existence of a region of stability on the P-T plane for red phosphorus was established. A qualitative phase diagram for phosphorus is presented; the red form is most stable at high temperatures and relatively low pressures. It is necessary to undertake careful investigations at pressures P < 0.3 GPa under pure hydrostatic conditions to make quantitative measurements.