Atomic and electronic structure of liquid iron trichloride.

This letter describes the combined use of high-energy X-ray diffraction and neutron diffraction to investigate the problem of the structure of liquid FeCl3. The results confirm the picture of liquid iron chloride consisting of closely packed Fe2Cl6 bitetrahedral molecules which have an atomic structure consistent with the electron diffraction results in the vapor. Comparison of the X-ray and neutron results at low Q suggests a paramagnetic moment about half that expected for a free Fe3+ ion, and confirms the picture suggested previously for topological and chemical short-range and intermediate-range order in the melt. Comparison of the X-ray diffraction data with molecular-dynamics results suggests a charge transfer intermediate between an atomic and fully ionic charge distribution, consistent with recent ab initio molecular orbital calculations.