Comparison of the data with the analytical fitted isotherms at high densities for the pressure normalized to the ideal atomic gas value, P∕n_atk_BT (panel a), and for the internal energy U (panel b). Symbols show the data: the IAPWS table (Wagner & Pruß 2002, straight crosses); results of ab initio calculations by Soubiran & Militzer (2015; empty diamonds); ab initio calculations by French et al. (2009; oblique crosses for liquid, inverted triangles for ice X, filled diamonds for the superionic [SI] phase, asterisks for the plasma phase); and the results of our present ab initio calculations (filled triangles for the SI phase and filled dots for the plasma phase), supplemented with our TFMD calculations at ρ > 50 g cm⁻³ (empty circles). Solid lines represent the present fit; the dotted line represents the fit of French & Redmer (2015) for ice X at T = 1000 K.