Jauch, W.; Reehuis, M.: Reassessment of the electron density in Cu2O using γ-ray diffraction. Acta Crystallographica Section B - Structural Science 70 (2014), p. 983-988
10.1107/S2052520614021866
Open Accesn Version

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 gamma-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 dz2 orbital, (ii) an incomplete ionization of Cu and O, (iii) no interstitial Cu-Cu charge pileup, thereby refuting the covalent bonding hypothesis.