Synchrotron X-ray analysis of the electron density in CoF2 and ZnF2

Accurate structure factors for small crystals of the rutile-type structures CoF2, cobalt difluoride, and ZnF2, zinc difluoride, have been measured wit h focused lambda = 0.8400 (2) Angstrom synchrotron X-radiation at room temp erature. Phenomenological structural trends across the full series of rutil e-type transition metal difluorides are analysed, showing the importance of the metal atom in the degree of distortion of the metal-F-6 octahedra in t hese structures. Multipole models reveal strong asphericities in the electr on density surrounding the transition metals, which are consistent with exp ectations from crystal field theory and the structural trends in these comp ounds, Transition metal 3d-orbital populations were computed from the multi pole refinement parameters, showing significant repopulation of orbitals co mpared with the free atom, particularly for CoF2.