Refined description of liquid and supercooled silicon from ab initio simulations

Despite silicon being of great technological importance, an understanding of its behavior across the phase diagram is still lacking, especially near liquid-solid coexistence. The difficulty in describing silicon near coexistence from first principles lies in discriminating between the metallic and covalent bonds present in the material. Using the strongly constrained and appropriately normed (SCAN) density functional, which can describe a wide variety of bonds with quantitative accuracy, we report a thorough investigation of liquid silicon in the vicinity of liquid-solid coexistence using ab initio molecular dynamics simulations. We observe a structural transition in the supercooled regime that is rooted in a change in the electronic structure of the material. This transition is found to occur at a higher temperature than previous predictions. We also discuss implications of the observed change in interatomic interactions for empirical models of transitions between two distinct liquids.