Experimental data and theoretical predictions on H₂–H₂O miscibility. (a) Experimental data for 1:1 H₂–H₂O miscibility from Seward & Franck (1981) (purple), Bali et al. (2013) (yellow), and Vlasov et al. (2023) (green); and the computational predictions of Bergermann et al. (2021) (light blue curve) and Bergermann et al. (2024) (blue curve). Filled symbols correspond to the coexistence of two phases, while empty squares refer to complete mixing of H₂ and H₂O. The solid lines indicate the fit of the corresponding data points. (b) Extrapolated critical curves based on the data shown in panel a) and used to construct the phase diagrams (see text for details). The linear extrapolations of the data by Bali et al. (2013) beyond 3 GPa and up to 4 and 5 GPa are shown by the dashed yellow line. The three different extensions beyond 3.5 GPa for the Vlasov et al. (2023) data (flat, V23 conv-1800 K, and V23 conv-2000 K) are shown by green dotted, solid, and dashed lines, respectively. Finally, the blue curve is from Bergermann et al. (2024).