The interplay between the topology of nanoclusters and the characteristic of boson peak in As-S glasses

Highlights

• The glasses of As_xS_(100-x) with x = 20, 28.6, 45, 40, 50 were prepared.
• Specific heat C_p/T³ shows a nonlinear dependence of boson peak (BP) on composition.
• Longitudinal elastic moduli, Raman spectroscopy and C_p/T³ depend on composition.
• Correlation between type of nanocluster and C_p/T³ was found in As_xS_(100-x) glasses.
• Ring-like and branchy-like nanoclusters are a possible origin of BP.

Abstract

The combination of mean coordination and concentration dependencies of elastic modules and low-frequency Raman scattering of As-S glasses brings new information about the spectroscopic boson peak (SBP) behavior. The analysis of the characteristic temperature positions of the thermometric boson peak (TBP) and the magnitude of heat capacity of As-S glasses was performed. This study was focused on the As-S compounds from the first glass-forming region with particular attention to the compositions of flexible, intermediate, and stressed-rigid phases. The origin of SBP and TBP is expected to have a structural nature. The spectral features found in the super low-frequency region of Raman spectra were assigned to quasi-localized "soft" modes.

The sulfur-rich glass, g-As₂S₅, represents the intermediate phase with As_nS_m clusters containing closed ends and several "soft" nanoclusters. These soft clusters can be responsible for intrinsic quasi-localized "soft" modes, the overall rigidity of the system, and quasi-elastic light scattering.