Charge densities of iso-structural metal hexaborides, a transparent metal LaB6 and a semiconductor\nBaB6, have been determined using the d > 0.22 Ã?â?¦ ultra-high resolution synchrotron radiation X-ray\ndiffraction data by a multipole refinement and a maximum entropy method (MEM). The quality of the\nexperimental charge densities was evaluated by comparison with theoretical charge densities. The\nstrong inter-octahedral and relatively weak intra-octahedral boron-boron bonds were observed in\nthe charge densities. A difference of valence charge densities between LaB6 and BaB6 was calculated\nto reveal a small difference between isostructural metal and semiconductor. The weak electron lobes\ndistributed around the inter B6 octahedral bond were observed in the difference density. We found the\nelectron lobes are the conductive Ãâ?¬-electrons in LaB6 from the comparison with the theoretical valence\ncharge density. We successfully observed a spatial distribution of electrons near the Fermi level from the\nX-ray charge density study of the series of iso-structural solids.
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