Chain Breakage in the Supercooled Liquid - Liquid Transition and Re-entry of the λ-transition in Sulfur

Amorphous sulfur was prepared by rapid compression of liquid sulfur at temperatures above the lambda-transition for to preserve the high-temperature liquid structure. We conducted synchrotron high-energy X-ray diffraction and Raman spectroscopyto diagnose the structural evolution of amorphous sulfur from room temperature to post-lambda-transition temperature. Discontinuous changes of the first and second peaks in atomic pair-distribution-function, g(r), were observed during the transition from amorphous to liquid sulfur. The average first-neighbor coordination numbers showed an abrupt drop from 1.92 to 1.81. The evolution of the chain length clearly shows that the transition was accompanied by polymeric chains breaking. Furthermore, a re-entry of the lambda-transition structure was involved in the heating process. The amorphous sulfur, which inherits the post-lambda-transition structure from its parent melts, transformed to the pre-lambda-transition liquid structure at around 391 K. Upon further heating, the pre-lambda-transition liquid transformed to a post-lambda-transition s tructure through the well-known lambda-transition process. This discovery offers a new perspective on amorphous sulfur's structural inheritance from its parent liquid and has implications for understanding the structure, evolution and properties of amorphous sulfur and its liquids.