Anionogenic Mixed Valency in KxBa1–xO2?δ
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- 作者：Shivakumara Giriyapura ; Baomin Zhang ; Robert A. de Groot ; Gilles A. de Wijs ; Antonio Caretta ; Paul H. M. van Loosdrecht ; Winfried Kockelmann ; Thomas T. M. Palstra ; Graeme R. Blake
- 刊名：Inorganic Chemistry
- 出版年：2014
- 出版时间：January 6, 2014
- 年：2014
- 卷：53
- 期：1
- 页码：496-502
- 全文大小：372K
- ISSN：1520-510X
文摘
We have synthesized members of an isostructural solid solution series KxBa1鈥?i>xO2鈭捨?/sub> (x < 0.41, 未 < 0.11) containing mixed-valent dioxygen anions. Synthesis in liquid ammonia solution allows a continuous range of compounds to be prepared. X-ray and neutron diffraction show that KxBa1鈥?i>xO2鈭捨?/sub> adopts the tetragonal rocksalt-derived structure of the end members KO2 and BaO2, without any structural phase transition down to 5 K, the lowest temperature studied here. We identify four oxygen鈥搊xygen stretching modes above 750 cm鈥? in the measured Raman spectra, unlike the spectra of KO2 and BaO2 which both contain just a single mode. We use density functional theory calculations to show that the stretching modes in KxBa1鈥?i>xO2鈭捨?/sub> arise from in-phase and anti-phase coupling of the stretching of nearest-neighbor oxygen dimers when the valence state of the dimers lies between 鈭? and 鈭? because of mixed cation coordination. This coupling is a direct signature of a novel type of anionogenic mixed valency.