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

    Research output: Contribution to journalArticleAcademicpeer-review

    3 Citations (Scopus)

    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.
    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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