Identifying a Structural
Preference in Reduced Rare-Earth
Metal Halides by Combining Experimental and Computational Techniques
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Abstract
The structures of two new cubic {TnLa<sub>3</sub>}Br<sub>3</sub> (Tn = Ru, Ir; <i>I</i>4<sub>1</sub>32, <i>Z</i> = 8; Tn = Ru: <i>a</i> = 12.1247(16) Å, <i>V</i> = 1782.4(4) Å<sup>3</sup>; Tn = Ir: <i>a</i> = 12.1738(19)
Å, <i>V</i> = 1804.2(5) Å<sup>3</sup>) compounds
belonging to a family of reduced rare-earth metal halides were determined
by single-crystal X-ray diffraction. Interestingly, the isoelectronic
compound {RuLa<sub>3</sub>}I<sub>3</sub> crystallizes in the monoclinic
modification of the {TnR<sub>3</sub>}X<sub>3</sub> family, while {IrLa<sub>3</sub>}I<sub>3</sub> was found to be isomorphous with cubic {PtPr<sub>3</sub>}I<sub>3</sub>. Using electronic structure calculations, a
pseudogap was identified at the Fermi level of {IrLa<sub>3</sub>}Br<sub>3</sub> in the new cubic structure. Additionally, the structure attempts
to optimize (chemical) bonding as determined through the crystal orbital
Hamilton populations (COHP) curves. The Fermi level of the isostructural
{RuLa<sub>3</sub>}Br<sub>3</sub> falls below the pseudogap, yet the
cubic structure is still formed. In this context, a close inspection
of the distinct bond frequencies reveals the subtleness of the structure
determining factors
