Relative difference in density between the CMS19+HG23 (Chabrier et al. 2019; Howard & Guillot 2023) and SCvH95 (Saumon et al. 1995) EOSs. Blue regions on the T–P diagram indicate where CMS19+HG23 is denser than SCvH95, while red regions highlight less dense areas. The coloured solid and dashed lines show T–P profiles of some models (using CMS19+HG23) from Fig. 1, at 0.1 or 10 Gyr. The dotted square indicates the region of the ab initio presented by Militzer & Hubbard (2013). The CMS19+HG23 EOS is more accurate in this region. The hashed area corresponds to the region where hydrogen becomes solid (see e.g. Chabrier et al. 2019).