Isobaric phase diagram for the MgSiO₃–H₂ binary system as determined by L. Stixrude & T. Gilmore (2025). The one- and two-phase regions outside and inside of the binodal are indicated. A region of metastable compositions for two coexisting phases exists between the binodal and spinodal curves. The compositions of two stable phases at approximately 3600 K are shown by way of example with a dashed tie line connecting them.