Ab Initio Comparison of Bonding Environments and Threshold Behavior in GexAs10Se90–x and GexSb10Se90–x Glass Models

Opletal, George; Drumm, Daniel W.; Petersen, Timothy; Wang, Rongping; Russo, Salvy P.

doi:10.1021/acs.jpca.5b00039

Cited by 5 publications

(7 citation statements)

References 31 publications

(87 reference statements)

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“…For Ge–As(Sb)–Se(Te) glasses, this means that the Ge, As(Sb), and Se(Te) atoms have four, three, and two nearest neighbors, respectively. This rule has been verified for all participating elements in Ge–As–Se, − Ge–As–Te, and Ge–Sb–Te. , There is less evidence for the validity of the Mott rule in Ge–Sb–Se glasses: ab initio molecular dynamics simulations have shown that they roughly follow this rule …”

Section: Introductionmentioning

confidence: 92%

Chemical Short-Range Order in Selenide and Telluride Glasses

et al. 2016

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The structure of Ge20SbxSe80-x (x = 5, 15, 20) glasses was investigated by neutron diffraction, X-ray diffraction, and extended X-ray fine structure measurements at the Ge, Sb, and Se K-edges. For each composition, large-scale structural models were obtained by fitting simultaneously the experimental data sets in the framework of the reverse Monte Carlo simulation technique. It was found that the structures of these glasses can be described mostly by the chemically ordered network model. Ge-Se and Sb-Se bonds are preferred; Se-Se bonds in the Se-poor composition (x = 20) and M-M (M = Ge, Sb) bonds in strongly Se-rich glass (x = 5) are not needed. The quality of the fits was significantly improved by introducing Ge-Ge bonding in the nearly stoichiometric composition (x = 15), showing a violation of chemical ordering. The structure of Ge20SbxSe80-x was compared to that of several glasses from the three analogous systems (Ge-As-Se, Ge-As-Te, Ge-Sb-Te), and it was found that chemical short-range order becomes more pronounced upon substituting As with Sb and Se with Te. Ge-As-Se glasses behave as random covalent networks over a very broad composition range. Chemical short-range order and disorder coexist in both Te-rich and Te-poor Ge-As-Te glasses, whereas amorphous Ge14Sb29Te57 and Ge22Sb22Te56 are governed by strict chemical preferences.

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Section: Introductionmentioning

confidence: 92%

Chemical Short-Range Order in Selenide and Telluride Glasses

et al. 2016

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“…% sample, post fiber-drawing, which is compared to the monoclinic GeSe 2 (ICDD-PDF-01-071-0117) and orthorhombic Sb 2 Se 3 (ICDD-PDF-01-072-1184) standards. Although the full 200 data point sets for each standard have been compared with those of the stoichiometric Ge 25 39 who identified using XRD both Sb 2 Se 3 and GeSe 2 phases crystallizing on heat treatment of Ge 32.5 Sb 7.5 Se 60 at.%; Ge was 32 at.% and Sb 7.5 at. %, yet Sb 2 Se 3 diffraction peaks of substantial intensity were readily identifiable in the XRD pattern.…”

Section: Crystallization In Ge-sb-se Glasses Relevant To Fiber Drawingmentioning

confidence: 99%

“…% thermogram rather than the liquidus shown as T m in Figure 7b. Accordingly, the exothermic peak appearing approximately 80°C below the solidus, was identified as the crystallization transition (T c ) in the stoichiometric Ge 25 and T c2 and the endothermic peaks of T m1 and T m2 (see inset in Figure 7) were both~8°C. A similar DT had already been observed by Wakkad et al, 41 who also reported an overlap within the DTA crystallization peak of Ge-Sb-Se glasses, heated at 10°C/min.…”

Section: Crystallization In Ge-sb-se Glasses Relevant To Fiber Drawingmentioning

confidence: 99%

“…For binary systems, such as As–Se, and ternary systems, such as Ge–As–Se, where all of the elements concerned have similar atomic masses and radii, the relationship between physical properties and the MCN is relatively well understood . However, for the Ge–Sb–Se glasses, the elemental Sb has a larger atomic radius than its neighboring Ge or Se, topological models are not as accurate in predicting their physical properties and these are dictated more by their chemical composition‐ a relationship that is less well understood at present.…”

Section: Introductionmentioning

confidence: 99%

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Compositional dependence of crystallization in Ge–Sb–Se glasses relevant to optical fiber making

et al. 2017

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For fiber-optic mid-infrared bio-and chemical-sensing, Ge-Sb-Se glass optical fibers are more attractive than Ge-As-Se because of: (i) lowered toxicity and (ii) lower phonon energy and hence transmission to longer wavelengths, with potential to reach the spectral "fingerprint region" for molecular sensing. There is little previous work on Ge-Sb-Se fibers. Here, fibers are fabricated from two glass compositions in the Ge x Sb 10 Se 90Àx atomic (at.) % series. Both glass compositions are of similar mean-coordination-number, lying in the overconstrained region, yet of different chemical composition: stoichiometric Ge 25 Sb 10 Se 65 at. % and non-stoichiometric Ge 20 Sb 10 Se 70 at. %. Thermal analysis on bulk glasses has previously shown that the former exhibited the maximum glass stability of the series. However, during fiber-drawing of Ge 25 Sb 10 Se 65 at. %, the preform tip is found to undergo surfacedevitrification to monoclinic GeSe 2 alone, the primary phase, no matter if the preform is an annealed, as-melted rod or annealed, extruded rod. The heating rate of the preform-tip to the fiber-drawing temperature is estimated to be up to~100°C/min tõ 490°C. Lower heating rates of 10°C/min using thermal analysis, in contrast, encourage crystallization of both Sb 2 Se 3 and GeSe 2 . The non-stoichiometric: Ge 20 Sb 10 Se 70 at. % composition drew successfully to low optical loss fiber, no matter whether the preform was an annealed, as-melted rod or annealed, extruded rod.

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“…Combinations of these two constraint categories have been previously used to prepare starting configurations for ab initio MD simulation . There exists some difficulty in gauging the effectiveness of these constraint combinations in increasing the uniqueness of the resulting model.…”

Section: Introductionmentioning

confidence: 99%

On reverse Monte Carlo constraints and model reproduction

et al. 2017

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Reverse Monte Carlo (RMC) simulations were performed to investigate the effectiveness of any combination of five experimentally motivated constraints on the reproduction of a test case, a ternary ab initio model. It was found that low energy structures fitting a variety of constraints commonly used in the RMC methodology could still provide an incorrect description of the chemical structural unit populations in multi-elemental systems. It is shown that the use of an elemental bond type constraint is an effective way to avoid this. © 2017 Wiley Periodicals, Inc.

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Ab Initio Comparison of Bonding Environments and Threshold Behavior in Ge_xAs₁₀Se_90–x and Ge_xSb₁₀Se_90–x Glass Models

Cited by 5 publications

References 31 publications

Chemical Short-Range Order in Selenide and Telluride Glasses

Chemical Short-Range Order in Selenide and Telluride Glasses

Compositional dependence of crystallization in Ge–Sb–Se glasses relevant to optical fiber making

On reverse Monte Carlo constraints and model reproduction

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