Crystal Structure of the Quaternary Compounds Li1.25Cd1.67In0.47Cl6 and Li0.21Mn1.71In0.79Cl6.

Abstract The quaternary chlorides “LiMInCl6” (M=Mg, Mn, Fe, Co, and Cd) reveal high lithium ion conductivity [Solid State Ionics 95 (1997) 173]. Single crystals of the cadmium and the manganese compounds are grown from melts of stoichiometric mixtures of the binary chlorides. The structures of the crystals were determined by X-ray single-crystal techniques. The obtained white Li1.25Cd1.67In0.47Cl6 crystals crystallize in a highly disordered CdCl2-type structure (space group R 3 m , Z=1, a=379.2(1) and c=1767.2(4) pm, R1=6.23%, 108 unique reflections (I>2σI)). The octahedral metal ion 3a site of the structure is randomly occupied by Li+, Cd2+, and In3+ ions. An additional amount of Cd2+ ions is localized in the Van der Waals gap on the likewise octahedral interstitial 3b site. This CdCl2-type structure obviously corresponds to the structure of the high-temperature polymorphs of the quaternary chlorides under discussion. The pale pink Li0.21Mn1.71In0.79Cl6 crystals, the structure of which is obviously that of the room-temperature polymorphs of this series, crystallize in a filled AlCl3-type, ordered CdCl2 superstructure (space group C2/m, Z=2, a=642.0(1), b=1110.6(2), and c=629.2(4) pm, β=110.08(3)°, R1=3.83%, 423 unique reflections (I>2σI)). Of the two metal ions sites the 2b site is occupied by the Li+ and In3+ ions, the 4g solely by Mn2+ ions. In the Van der Waals gap of this structure no electron density is observed. The distortion factors ρ and σ of CdCl2-type structures [J. Solid State Chem. 95 (1991) 176] are discussed with respect to occupation of interstitial sites in the Van der Waals gap.