This study presents a comprehensive investigation of the liquid-liquid phase transition in lithium under extreme pressures (0-80 GPa) at constant temperature 600 K. By integrating machine learning potentials (MLP) with first-principles calculations, we reveal a pressure-induced electronic transition in liquid lithium that mirrors the transfer of electrons from s orbitals to p orbitals and the localization of valence electrons in solid lithium. At around 30 GPa, liquid lithium transitions from an isotropic liquid dominated by s-electrons to a covalent liquid dominated by p-electrons, accompanied by the extremum of the valence band width and the singularity of thermodynamic properties. In addition, the degree of electron localization increases with pressure and gradually tends to saturate, which leads to the anomalous melting line and diffusion behavior of liquid lithium. These findings not only elucidate the complex electronic behavior of liquid alkali metals under extreme compression, but also provide crucial insights into the universal behavior of alkali metals under high-pressure environments.

 

liquid liquid phase transition,lithium,machine learning potential,high temperature and high pressure,Electronic structure