Dynamical Crossover at the Liquid-Liquid Transformation of a Compressed Molten Alkali Metal

Taras Bryk, Simone De Panfilis, Federico A. Gorelli, Eugene Gregoryanz, Michael Krisch, Giancarlo Ruocco, Mario Santoro, Tullio Scopigno, Ari P. Seitsonen
2013 Physical Review Letters  
Density-driven phase transformations are a known phenomenon in liquids. Pressure-driven transitions from an open low-density to a higher-density close-packed structure were observed for a number of systems. Here, we show a less intuitive, inverse behavior. We investigated the electronic, atomic, and dynamic structures of liquid Rb along an isothermal line at 573 K, at 1.2-27.4 GPa, by means of ab initio molecular dynamics simulations and inelastic x-ray scattering experiments. The excellent
more » ... . The excellent agreement of the simulations with experimental data performed up to 6.6 GPa validates the overall approach. Above 12.5 GPa, the breakdown of the nearly-free-electron model drives a transition of the pure liquid metal towards a less metallic, denser liquid, whose first coordination shell is less compact. Our study unveils the interplay between electronic, structural, and dynamic degrees of freedom along this liquid-liquid phase transition. In view of its electronic nature, we believe that this behavior is general for the first group elements, thus shedding new light into the high-pressure properties of alkali metals. P (2013). Dynamical crossover at the liquidliquid transformation of a compressed molten alkalI metal. Physical Review Letters, 111(7):077801. Abstract Density driven phase transformations are a known phenomenon in liquids. Pressure driven transitions from an open low density to a higher density close packed structure were observed for a number of systems. Here we show a less intuitive, inverse behaviour. We investigated the electronic and atomic structures of liquid Rb along an isothermal line at 573 K, at 1.2−27.4 GPa, by means of ab initio molecular dynamics simulations and inelastic x-ray scattering experiments. The excellent agreement of the simulations with experimental data performed up to 6.6 GPa validates the overall approach. Above 12.5 GPa the breakdown of the nearly-free electron model drives a transition of the pure liquid metal towards a less metallic, denser liquid, whose first coordination shell is less compact. Our study unveils the interplay between electronic, structural and dynamic degrees of freedom along this liquid-liquid phase transition. In view of its electronic nature, we believe that this behavior is general for the first group elements, thus shedding new light into the high pressure properties of alkali metals.
doi:10.1103/physrevlett.111.077801 pmid:23992083 fatcat:pg6zjziglbdaxehyfvhpklvivu