Mechanical and Chemical Thresholds in IV-VI Chalcogenide Glasses

Ac Conductivity and Dielectric Properties of Amorphous Ge15Se60X25( X = As or Sn) Films

“…By assuming ν ph = 10 12 Hz and α −1 = 10 Å [33], the density of localized states N (E f ) is calculated at different frequencies and at 303 K for the studied samples. The obtained values of N (E f ) are given in Table I for the studied composition films.…”

Pressure-induced structural changes in the network-forming isostatic glassGeSe4: An investigation by neutron diffraction and first-principles molecular dynamics

“…At pressures beyond this threshold, the FPMD results show an increase inn that is more rapid than found from diffraction, where homopolar bonds play a mediating role in the appearance of higher coordinated Ge and Se atoms [34,35]. The pressure-dependent properties of the isostatic glass GeSe 4 have also been probed by x-ray diffraction [43,44], Raman spectroscopy [44], and electrical conductivity [40,41,44] methods. A discontinuous increase in the electrical conductivity is reported at a pressure that accompanies the transformation from a low-density semiconducting glass to either a high-density metallic glass in the range 10-12 GPa (Ref.…”

“…A discontinuous increase in the electrical conductivity is reported at a pressure that accompanies the transformation from a low-density semiconducting glass to either a high-density metallic glass in the range 10-12 GPa (Ref. [44]) or a metallic crystal at ∼10.5 GPa [40,41]. There is disagreement, however, between the x-ray diffraction results regarding the pressure-dependent structure, e.g., in respect to the rate of change ofn with increasing density [43,44].…”

“…For example, the pressure-dependent properties of the stressed-rigid glass GeSe 2 have been probed by x-ray and neutron diffraction [33][34][35][36], x-ray absorption spectroscopy [36], Raman spectroscopy [37,38], sound velocity [39], electrical conductivity [40,41], and first-principles molecular dynamics (FPMD) [34,42] methods. It is unclear, however, as to whether there is an abrupt semiconductor-glass to metal-crystal transition [40,41], or a gradual evolution in the structure to give a more metallic glass [33][34][35][36]42], the details of which may be sensitive to the thermal history [34]. At pressures below ∼8.5 GPa, neutron diffraction and FPMD results reveal a self-consistent picture in which there is no change ton but a trade-off between the fractions of corner-and edge-sharing tetrahedra with increasing density.…”

Material functionalities from molecular rigidity: Maxwell’s modern legacy

“…3 For instance, in multicomponent chalcogenide glasses containing an important fraction of Group VI elements (S, Se, Te) or in multicomponent oxides, such rules permit determining the fl exible-torigid transition due to the presence of anomalies or thresholds in various physicochemical properties, as detected from Raman scattering, 5 stress relaxation and viscosity measurements, 6 vibrational density of states, 7 Brillouin scattering, 8 and resistivity. 9 However, for many other systems, including the important classes of oxides, silicates, or borosilicates, which represent the base material for many domestic and industrial applications in glass science, the question of a well-defi ned coordination number has been a long-standing issue. This has been resolved 10 with the support of molecular dynamics (MDs)-based constraint-counting algorithms that have permitted extension of our understanding to the next level.…”