Anionogenic Mixed Valency in KxBa1−xO2−δ

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*

*Bijbehorende auteur voor dit werk

OnderzoeksoutputAcademicpeer review

3 Citaten (Scopus)
385 Downloads (Pure)


We have synthesized members of an isostructural solid solution series KxBa1-xO2-delta (x <0.41, delta <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-xO2-delta 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-oxygen stretching modes above 750 cm(-1) 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-xO2-delta 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 -1 and -2 because of mixed cation coordination. This coupling is a direct signature of a novel type of anionogenic mixed valency.

Originele taal-2English
Pagina's (van-tot)496-502
Aantal pagina's7
TijdschriftInorganic Chemistry
Nummer van het tijdschrift1
StatusPublished - 6-jan-2014

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