Is there a liquid-liquid transition in the AsS melt ?

This proposal aims at studying the liquid phase of As4S4 (realgar) in order to determine whether a first-order liquid-liquid transition (LLT) exists between a molecular and a polymeric liquid under high P-T conditions. Such examples of first-order transition in the liquid state remain scarce, and this phenomena is poorly understood. Previous experimental and theoretical studies of the AsS melt suggest that a LLT exists in this system but a firm experimental proof is lacking. Here, using the state-of-the-art facilities of ID27, we will perform the first direct experimental density measurements combined with x-ray diffraction (XRD) to establish and characterize the LLT in AsS.