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*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

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.

Original languageEnglish
Pages (from-to)496-502
Number of pages7
JournalInorganic Chemistry
Volume53
Issue number1
DOIs
Publication statusPublished - 6-Jan-2014

Keywords

  • INELASTIC NEUTRON-SCATTERING
  • INITIO MOLECULAR-DYNAMICS
  • AUGMENTED-WAVE METHOD
  • HYPEROXIDES
  • SYSTEMS
  • MAGNETOGYRATION
  • FERROMAGNETISM
  • SPECTROSCOPY
  • PEROXIDES
  • GRAPHITE

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