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

Abstract

Amorphous sulfur was prepared by rapid compression of liquid sulfur at temperatures above the λ-transition for to preserve the high-temperature liquid structure. We conducted synchrotron high-energy X-ray diffraction and Raman spectroscopy to diagnose the structural evolution of amorphous sulfur from room temperature to post-λ-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 λ-transition structure was involved in the heating process. The amorphous sulfur, which inherits the post-λ-transition structure from its parent melts, transformed to the pre-λ-transition liquid structure at around 391 K. Upon further heating, the pre-λ-transition liquid transformed to a post-λ-transition structure through the well-known λ-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.

A Study of the Pressure-Induced Solidification of Polymers

“…The rapid compression experiment of sulfur melt obtained bulk amorphous sulfur ( a -S). This a -S possesses a much higher content of polymeric chains than its parent liquid [20]. Figure 5a shows the Raman pattern of the a -S at 273 K, which was obtained by compressing liquid sulfur at around 453 K. The Raman peaks located at 461 cm −1 and 472 cm −1 are assigned to the bond-stretching modes of the polymeric chains’ S μ and S 8 rings, respectively [20].…”

“…This a -S possesses a much higher content of polymeric chains than its parent liquid [20]. Figure 5a shows the Raman pattern of the a -S at 273 K, which was obtained by compressing liquid sulfur at around 453 K. The Raman peaks located at 461 cm −1 and 472 cm −1 are assigned to the bond-stretching modes of the polymeric chains’ S μ and S 8 rings, respectively [20]. Their area ratio, A 461 / A 472 , provides a reasonable fingerprint on the content of the rings and chains [20].…”

“…Figure 5a shows the Raman pattern of the a -S at 273 K, which was obtained by compressing liquid sulfur at around 453 K. The Raman peaks located at 461 cm −1 and 472 cm −1 are assigned to the bond-stretching modes of the polymeric chains’ S μ and S 8 rings, respectively [20]. Their area ratio, A 461 / A 472 , provides a reasonable fingerprint on the content of the rings and chains [20]. The polymeric chains’ content was about 73 wt%; the majority content is polymeric chains in the a -S [20].…”

“…Their area ratio, A 461 / A 472 , provides a reasonable fingerprint on the content of the rings and chains [20]. The polymeric chains’ content was about 73 wt%; the majority content is polymeric chains in the a -S [20]. This value is obviously higher than that in the parent liquid, which was about 30 wt% at 453 K in Figure 5a [20].…”

Raman measurements using a field‐widened spatial heterodyne Raman spectrometer

“…It is a popular method and technique for identification and analysis because it is nondestructive, requires no sample preparation, and both organic and inorganic substances can be measured in various states. Owing to these advantages, Raman spectroscopy has already been applied in a variety of fields, including physics, chemistry, biology, medicine, geology, and electronics . A spatial heterodyne Raman spectrometer (SHRS) possesses the multiple advantages, a larger entrance or higher light throughput than that a dispersion system, high spectral resolution, a compact, and rugged package without moving parts, and is compatible with a pulsed laser and gated detectors under ambient light conditions .…”