Exothermic Supercooled Liquid–Liquid Transition in Amorphous Sulfur

Amorphous sulfur (a-S) is prepared by rapidly compressing molten sulfur to high pressure. From differential scanning calorimeter measurements, a large exothermic peak has been observed around 396 K. Online wide-angled x-ray scattering spectra indicate that no crystallization occurs in the temperature range 295–453 K, suggesting that the exothermal process corresponds to an amorphous-to-amorphous transition. The transition from amorphous sulfur to liquid sulfur is further verified by the direct observation of sulfur melt at the temperature of the associated transition. This is the first time of reporting that a-S transforms to liquid sulfur directly, which has avoided a crystallization process. What is more, the transition is an exothermic and a volume expansion process.