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Giriyapura S, Zhang B, de Groot RA, et al. Anionogenic mixed valency in KxBa1-xO2-δ. Inorg Chem. 2013;53(1):496-502doi: 10.1021/ic402493q.
Giriyapura, S., Zhang, B., de Groot, R. A., de Wijs, G. A., Caretta, A., van Loosdrecht, P. H., Kockelmann, W., Palstra, T. T., & Blake, G. R. (2014). Anionogenic mixed valency in KxBa1-xO2-δ. Inorganic chemistry, 53(1), 496-502. https://doi.org/10.1021/ic402493q
Giriyapura, Shivakumara, et al. "Anionogenic mixed valency in KxBa1-xO2-δ." Inorganic chemistry vol. 53,1 (2014): 496-502. doi: https://doi.org/10.1021/ic402493q
Giriyapura S, Zhang B, de Groot RA, de Wijs GA, Caretta A, van Loosdrecht PH, Kockelmann W, Palstra TT, Blake GR. Anionogenic mixed valency in KxBa1-xO2-δ. Inorg Chem. 2014 Jan 06;53(1):496-502. doi: 10.1021/ic402493q. Epub 2013 Dec 11. PMID: 24328297.
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Inorg Chem. 2014 Jan 06;53(1):496-502. doi: 10.1021/ic402493q. Epub 2013 Dec 11.

Anionogenic mixed valency in KxBa1-xO2-δ.

Inorganic chemistry

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

Affiliations

  1. Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.

PMID: 24328297 DOI: 10.1021/ic402493q

Abstract

We have synthesized members of an isostructural solid solution series KxBa1-xO2-δ (x < 0.41, δ < 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-δ 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-δ 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.

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