Phase transitions in uranium dioxide at high pressures and temperatures

The melting curve is plotted for uranium dioxide with fluorite structure in a pressure range from −2.5 to +100 GPa. This curve has a peak at the point 3348 K, 6 GPa, and has a negative derivative at high pressures. The pressure corresponding to a polymorphic transition of uranium dioxide (37 GPa) at a temperature of 1015 K is determined. The slope of the equilibrium curve of the polymorphic transition in UO₂ in the temperature range 300–1000 K is − 56 K/GPa.