More May Be Less

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• 作者：James E. Gillespie
• 关键词：Chalcogenides ; Nuclear magnetic (and quadrupole) resonance
• 刊名：Ophthalmology
• 出版年：2008
• 期刊代码：211_01616420
• 类别：med
• 出版时间：July 2008
• 卷：115
• 期：7
• 页码：1266
• 文件大小：48 K

摘要

The local bonding structure in the Ge–As–Se ternary glassy system has been investigated by ⁷⁵As nuclear quadrupole resonance (NQR) at 77 K. For the compositions with average coordination number the NQR measurements yield no evidence for the presence of As–As homopolar bonds. For the composition Ge₂As₂Se₅ () the NQR lineshape exhibits two peaks corresponding to arsenic sites with zero (or three) and two As–As bonds. High Ge and As content leads to formation of microclusters, where the predominant structural units are, possibly, As₄Se₄ molecules or partial molecules with As–As bonds. The NQR spectrum for the composition Ge_0.33As_0.12Se_0.55 () shows a weak peak corresponding to an arsenic site with zero (or three) homobonds and two resolved peaks in the high frequency region. Such behavior is consistent with an increase in inhomogenity in the local structure and perhaps nanoscale phase separation.