X-ray charge density study of chemical bonding in skutteruditeCoSb3

Abstract

The experimental charge density of nondoped $\mathrm{Co}{\mathrm{Sb}}_{3}$ has been determined by the maximum entropy method (MEM) using low temperature $(10\phantom{\rule{0.3em}{0ex}}\mathrm{K})$, short wavelength $(0.42\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}})$, and high-resolution $({d}_{\mathrm{min}}=0.33\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}})$ synchrotron x-ray powder diffraction data measured at SPring-8, Japan. The MEM charge density clearly reveals three types of charge density overlap between atoms in $\mathrm{Co}{\mathrm{Sb}}_{3}$. The four Sb atoms form an ${\mathrm{Sb}}_{4}$ ring, and the MEM charge densities at two types of Sb-Sb midpoints are 0.35 and $0.50\phantom{\rule{0.3em}{0ex}}e\phantom{\rule{0.2em}{0ex}}{\mathrm{\AA{}}}^{\ensuremath{-}3}$. The charge density overlap between the Co and Sb atoms at the midpoint is $0.52\phantom{\rule{0.3em}{0ex}}e\phantom{\rule{0.2em}{0ex}}{\mathrm{\AA{}}}^{\ensuremath{-}3}$, which is larger than the values observed at the Sb-Sb midpoints. The nature of the chemical bonding observed in the present MEM charge density is consistent with a previous theoretical study by Lefebvre-Devos et al. [Phys. Rev. B 63, 125110 (2001)].