Electride transition in liquid aluminum under high pressure and high temperature

Despite the conventional view of liquid aluminum (l-Al) as a simple metal governed by the free-electron model, it exhibits unique bonding characteristics. This study uncovers a gradual transition from free electron to electride behavior in l-Al at high pressure and temperature, forming a type of two-component liquid where atomic and electride states coexist. The proportion of electride increases with pressure and temperature until reaching saturation, leading to notable changes in the pair-correlation function and coordination number of l-Al at saturation pressure. Furthermore, this electride transition was found to profoundly impact the thermodynamic and dynamic properties, as evidenced by anomalous crossovers in the isothermal bulk modulus, thermal expansivity, heat capacity, sound speed, and self-diffusion coefficient correlated with varying pressure and temperature. The finding of the anomalous behavior of l-Al described in this work will deepen our understanding of the electronic structure and also lay ground work for interpreting and predicting new physical and chemical behavior under extreme conditions.