title: Reassessment of the electron density in Cu2O using γ-ray diffraction.
abstract: The electron-density distribution in Cu2O has been critically reexamined to test controversial conclusions from earlier experimental and theoretical studies. The electron density is derived via multipole refinement of high-quality single-crystal diffraction data, collected at room temperature with 316.5 keV gamma radiation. Four γ-lines in the energy range 200-600 keV have been used to extrapolate extinction-free low-order structure factors. The remaining extinction corrections refine to a crystal mosaicity identical to the observed one. There is no support for anharmonic contributions to the thermal parameters. Important features of the derived electron density are (i) a partially filled d_{z^2} orbital, (ii) an incomplete ionization of Cu and O, and (iii) no interstitial Cu-Cu charge pileup, thereby refuting the covalent bonding hypothesis.
authors.affiliation: Helmholtz-Zentrum Berlin fur Materialien und Energie, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Jauch
authors.affiliation: Helmholtz-Zentrum Berlin fur Materialien und Energie, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany.
authors.forename: Manfred
authors.initials: M
authors.lastname: Reehuis
keywords: electron-density distribution; high-temperature superconductors; γ-ray radiation