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Intricate Li–Sn Disorder in Rare-Earth Metal–Lithium Stannides. Crystal Chemistry of RE3Li4–xSn4+x (RE = La–Nd, Sm; x < 0.3) and Eu7Li8–xSn10+x (x ≈ 2.0)
journal contribution
posted on 2018-04-20, 17:49 authored by Nian-Tzu Suen, Sheng-Ping Guo, James Hoos, Svilen BobevReported are the syntheses, crystal
structures, and electronic structures of six rare-earth metal–lithium
stannides with the general formulas RE3Li4–xSn4+x (RE = La–Nd,
Sm) and Eu7Li8–xSn10+x. These new ternary compounds have been
synthesized by high-temperature reactions of the corresponding elements.
Their crystal structures have been established using single-crystal
X-ray diffraction methods. The RE3Li4–xSn4+x phases crystallize
in the orthorhombic body-centered space group Immm (No. 71) with the Zr3Cu4Si4 structure
type (Pearson code oI22), and the Eu7Li8–xSn10+x phase crystallizes in the orthorhombic base-centered space group Cmmm (No. 65) with the Ce7Li8Ge10 structure type (Pearson code oC50). Both
structures can be consdered as part of the [RESn2]n[RELi2Sn]m homologous series, wherein the structures are intergrowths
of imaginary RESn2 (AlB2-like structure type)
and RELi2Sn (MgAl2Cu-like structure type) fragments.
Close examination the structures indicates complex occupational Li–Sn
disorder, apparently governed by the drive of the structure to achieve
an optimal number of valence electrons. This conclusion based on experimental
results is supported by detailed electronic structure calculations,
carried out using the tight-binding linear muffin-tin orbital method.