Pressure−temperature (P − T) conditions of the LHDAC experiments in this study (data points) shown with the melting curves of relevant materials: MgO (Kimura et al. 2017), (Mg_0.72Fe_0.28)O (Fu et al. 2018), FeO (Boehler 1992), FeH _x (Sakamaki et al. 2009), and H (Gregoryanz et al. 2003). No experiment in this study exceeded the melting temperature of MgO, while most were near or above the melting temperature of FeO and FeH _x . All experiments were conducted above the melting temperature of hydrogen.