Electron density distribution in paramagnetic chromium:: A γ-ray diffraction study

High-accuracy single-crystal structure factors, complete up to sin theta/lambda=1.78 angstrom(-) (1) have been measured from paramagnetic chromium at 333 K using 316.5 keV gamma radiation. A detailed description of the electron density distribution is derived in terms of a multipolar atomic deformation model. There is pronounced charge asphericity in the valence region arising from preferential occupancy of the t(2g) subshell. The 3d charge distribution is contracted by 12.6% relative to the free atom, in accordance with magnetic synchrotron x ray and neutron measurements. By contrast, the atomic crystal scattering factor deduced from gamma-ray diffraction is found to be in contradiction with earlier experimental and theoretical work. Achievement of a reliable Debye-Waller factor is of vital importance in this context. There is no evidence for an anharmonic term in the atomic potential. Real space and energetic features of the charge density topology are used to characterize the directed metallic bonds. Special attention is paid to the form factor approximation in diffraction data analysis.