Medium range order and structural relaxation in As–Se network glasses through FSDP analysis

Abstract

Synchrotron X-ray diffraction and neutron scattering studies are performed on As-Se glasses in two states: as-prepared (rejuvenated) and aged for ~23 years. The first sharp diffraction peak (FSDP) obtained from the structure factor data as a function of composition and temperature indicates that the cooperative processes that are responsible for structural relaxation do not affect FSDP. The results are correlated with the composition dependence of the complex heat capacity of the glasses and concentration of different structural fragments in the glass network. The comparison of structural information shows that density fluctuations, which were thought previously to have a significant contribution to FSDP, have much smaller contribution than the cation-cation correlations, presence of ordered structural fragments or cage molecules.

Effect of high‐energy mechanical milling on the medium‐range ordering in glassy As‐Se

“…Thus, it is clearly seen that with increase in Se content in under‐stoichiometric As x Se 100 − x (decrease in x parameter), the FSDP position shifts to higher scattering vectors Q 1 (Figures , , A), this effect for unmilled glasses being in an excellent agreement with known data . The FSDP becomes merely reduced in a height and broadened in a width Δ Q 1 reaching a maximum near eutectic As 20 Se 80 composition, and then rapidly drops with Se content (Figures , , B), these changes agreed with our preliminary research .…”

“…Similar compositional tendencies are also revealed in the low-Q part of the reduced X-ray structure factor F(Q) = Q(S(Q)−1) for these glasses depicted in Figure 4 Thus, it is clearly seen that with increase in Se content in under-stoichiometric As x Se 100 − x (decrease in x parameter), the FSDP position shifts to higher scattering vectors Q 1 (Figures 2, 4, 5A), this effect for unmilled glasses being in an excellent agreement with known data. 30,31,38 The FSDP becomes merely reduced in a height and broadened in a width ΔQ 1 reaching a maximum near eutectic As 20 Se 80 composition, and then rapidly drops with Se content (Figures 2, 4, 5B), these changes agreed with our preliminary research. 11 Contrary to the FSDP, the PDP reveals an opposite steady tendency with x decrease in peak position Q 2 (decrease, Figure 8A) and width ΔQ 2 (increase, Figure 8B).…”

“…The characteristic distance R (spacing of the FSDP-responsible quasi-periodicity) and correlation length L (over which this quasi-periodicity was maintained) were defined as: 14,[24][25][26][27][28][29][30][31] We also explore the concept of diffuse halos in the XRPD patterns of amorphous substances as arising from…”

Concepts and applications of rigidity in non-crystalline solids: a review on new developments and directions

“…This means that e.g. the total structure factor accessed from neutron or X-ray scattering may not represent a structural probe for the IP [11,99,103]. In this respect, neutron diffraction studies using the isotopic substitution method to provide the partial contributions to both structure factors and pair correlation functions [104] across the required range of compositions are highly desirable.…”

“…One should note that the experimental protocol used in [103,134,136] does not follow the one utilized for ageing studies in e.g. spin glasses for which the system is maintained in the glassy state at a fixed T/T g < 1 [137].…”