Pseudo‐self‐organized topological phases in glassy selenides for IR photonics

Abstract

Network‐forming cluster approach is applied to As‐Se and Ge‐Se glasses to justify their tendency to self‐organization. It is shown that reversibility windows determined by temperature‐modulated differential scanning calorimetry using short‐term aged or as‐prepared samples do not necessary coincide with self‐organized phase in these materials. The obtained results testify also pseudo‐self‐organization phenomenon in Ge‐Se glasses: over‐constrained outrigger raft structural units built of two edge‐ and four corner‐shared tetrahedra are interconnected via optimally‐constrained ≡Ge‐Se‐Se‐Ge≡ bridges within the range of compositions identified previously as self‐organized phase by temperature modulated differential scanning calorimetry technique. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Comment on “Molecular origin of aging of pure Se glass: Growth of inter-chain structural correlations, network compaction, and partial ordering” [J. Chem. Phys. 146, 224506 (2017)]

“…3, the scan rate was 5 • C/min which is quite close to 3 • C/min used as a typical MDSC scan rate by Dash et al 2 At such low scan rates (2-5 • C/min), the conclusions drawn from MDSC and conventional DSC would be quite similar, which has been convincingly proved at the example of As/Ge-Se glasses. 3,5,6 The narrowing of glass transition range W as a result of physical aging or annealing was also observed previously in pure Se, 7 a number of Se-based glasses, 8,9 and even organic polymers. 10 Moreover, in As-Se glasses, this narrowing was accompanied by changes in the asymmetry of non-reversing heat flow (∆H nr ) measured at 2 • C/min scan rate after ∼20 years of dark storage at room temperature.…”

“…15 The threshold time depends essentially on T a , decreasing when T a approaches T g ; i.e., t th is different for the glasses with different T g aged at the same temperature. As a result, the isochronal aging-induced changes in T g (especially as small as 2-4 • C) 2 T g , which varies from ∼40 • C for pure Se to about ∼70 • C for Ge 6 Se 94 glasses (see Fig. 4 in Ref.…”

Relaxation and physical aging in network glasses: a review

“…Although some other models [335,371] with a weaker theoretical basis have argued that the existence of the IP remains elusive, albeit contradicted by the variety of experimental signatures, there is a strong theoretical and numerical indication that RW or IP glasses display a particular relaxation kinetics manifesting in ∆H nr that leads to anomalous properties in different physical properties (Fig. 40).…”

Structural, dynamic, electronic, and vibrational properties of flexible, intermediate, and stressed rigid As-Se glasses and liquids from first principles molecular dynamics

“…107 The observation of these spectacular changes occurring within the x c1 < x < x c2 range requires special care in sample preparation because it has been shown that measurements are highly sensitive to dryness or homogeneity. 107,109,110 As an unfortunate consequence, there have been reported statements challenging 82,111,112 the existence of the intermediate phase.…”