R. G. Trønnes

Melting curves of Ca‐perovskite (pure CaSiO 3 ) were determined by ab initio density functional theory, using two solid‐liquid coexistence methods and two free energy approaches, in the form of thermodynamic integration and two‐phase thermodynamics. The melting curves based on the solid‐liquid coexistence methods and thermodynamic integration rise steeply from 2000 K at 14 GPa to 7000 K at 136 GPa. The melting temperature at 136 GPa is 1400 K higher than previous ab initio predictions. The high thermal stability of Ca‐perovskite is linked to its high‐symmetry isometric structure and consistent with experiments, demonstrating that Ca‐perovskite is the most refractory phase in basaltic compositions in the lower mantle pressure range. The steep dT/dp slope of the melting curve also shows that the Ca‐perovskite liquidus field expands relative to those of bridgmanite and silica with increasing pressure, in agreement with experimental evidence from simple and complex systems.