Temperature and pressure effects on the surface structure of liquid gallium

Liquid gallium exhibits a unique metallic-covalent coexistence. Leveraging the volume constant pressure molecular dynamics method and a well-trained neural network potential, we study the evolution of liquid Ga surface structures under varying temperatures and pressures. Our study presents a schematic P-T phase diagram of the liquid surface. We observe symmetric static structure factor main peaks in the outermost layers of the liquid Ga surface compared with asymmetric ones for inner layers, indicating a simple liquid behavior and a lack of Ga₂ dimers at the surface. We calculate the surface energy and the surface tension, which reveal non-monotonic changes. All these results provide a further insight into understanding the physics of the strange metal gallium.