Charge density and chemical bonding in cubic boron nitride

Abstract

The chemical bonding in cubic boron nitride, BN, is assessed by a charge density study from accurate single crystal X-ray diffraction data measured up to (sin θ λ ) max = 1.71 A ̊ −1 . A data set of 76 unique observed reflections is refined using the conventional independent atom model ( R = 0.0179, R w 0.0136), as well as using a “bond charge” model ( R = 0.0091, R w = 0.0080), and a multipole expansion model ( R = 0.0054, R w = 0.0056). Deformation density maps indicate both covalent bonding and a considerable charge transfer from boron towards nitrogen corresponding to their respective electronegativities. The transfer is estimated by a charge integration method to 0.46 electrons in good agreement with 0.42 electrons indicated by the refined monopole functions of the multipole expansion.