Figure 6.

Calculated enthalpies as a function of pressure for ScFeO₃ polymorphs: polar corundum (blue), perovskite (black), YMnO₃ (purple), ilmenite (red), and postperovskite (green) relative to the binary oxides (yellow). Upper plot: 0 K results, for FM (solid lines) and AFM (dashed lined) phases. Mid plot: 1773 K results, for the paramagnetic phase, where the blue area represents the contribution of the configurational entropy to the polar corundum, with the lower bound shown representing the maximum possible stabilizing contribtion. Both magnetic and configurational terms are essential for the polar corundum to become the stable phase between 0 and 12 GPa. Bottom diagram: temperature dependence of cation order in polar corundum SFO from MC simulations, showing a transition from a mainly ordered to a mainly disordered structure between 1300 and 1450 K.