Network-Forming Nanoclusters in Binary As–S/Se Glasses: From Ab Initio Quantum Chemical Modeling to Experimental Evidences

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• 作者：M. Hyla
• 关键词：Chalcogenide glasses ; Nanocluster ; Reversibility window ; Ab initio calculation
• 刊名：Nanoscale Research Letters
• 出版年：2017
• 出版时间：December 2017
• 年：2017
• 卷：12
• 期：1
• 全文大小：588KB
• 刊物主题：Nanotechnology; Nanotechnology and Microengineering; Nanoscale Science and Technology; Nanochemistry; Molecular Medicine;
• 出版者：Springer US
• ISSN：1556-276X
• 卷排序：12

文摘

Network-forming As₂(S/Se)_m nanoclusters are employed to recognize expected variations in a vicinity of some remarkable compositions in binary As–Se/S glassy systems accepted as signatures of optimally constrained intermediate topological phases in earlier temperature-modulated differential scanning calorimetry experiments. The ab initio quantum chemical calculations performed using the cation-interlinking network cluster approach show similar oscillating character in tendency to local chemical decomposition but obvious step-like behavior in preference to global phase separation on boundary chemical compounds (pure chalcogen and stoichiometric arsenic chalcogenides). The onsets of stability are defined for chalcogen-rich glasses, these being connected with As₂Se₅ (Z = 2.29) and As₂S₆ (Z = 2.25) nanoclusters for As–Se and As–S glasses, respectively. The physical aging effects result preferentially from global phase separation in As–S glass system due to high localization of covalent bonding and local demixing on neighboring As₂Se_m+1 and As₂Se_m−1 nanoclusters in As–Se system. These nanoclusters well explain the lower limits of reversibility windows in temperature-modulated differential scanning calorimetry, but they cannot be accepted as signatures of topological phase transitions in respect to the rigidity theory.