Example of a phase diagram T_dmx($P,x_{{\text{H}}_2\text{O}}$) based on the shape of the 0.2 GPa isobar according to the experimental data (purple points) of Seward & Franck (1981). Higher isobars are obtained by shifting the 0.2 GPa curve vertically according to the given critical curve T_dmx(P, 0.5). Here, the V23 conv-1800 K case is shown. x_A and x_B show the coexisting particle fractions at 3 GPa and 1400 K. The waterpoor equilibrium abundance x_A is used to compute the atmospheric abundance.