Fig. 1: Angular distribution functions at ambient and extreme conditions.

Probability distributions of angles (θ) between Na– and Cl–O bonds and the dipole of water molecules belonging to the ion first solvation shell (a, c, e, g), and the dipole of water molecules belonging to the shared Na–Cl shell (b, d, f, h), obtained with first principles molecular dynamics simulations. a–d and e–h show the results for CIP (red line), TIS (transition state between CIP and SIP; green line) and SIP (blue line) at 400 K and 1 atm and 1000 K and 11 GPa, respectively. The cutoff value used to define the first solvation shell is 3.2 (3.9) Å for Na⁺ (Cl⁻) ion, chosen as the first minima of the ion-O radial distribution function. Since we performed biased simulations (with an external force acting on the ions), we used a weighting scheme to recover unbiased statistics (see Supplementary Note 4).