RELixSn2 (RE = La�Nd, Sm, and Gd; 0 = x < 1), previously considered to be the stoichiometric RELiSn2 phases have been re-investigated. These materials crystallize with the base-centered orthorhombic space group Cmcm (No. 63), and can be formally assigned as a defect variant of the CeNiSi2 structure type (Pearson symbol oC16, figure 1). Our systematic single-crystal X-ray diffraction studies revealed substantial Li-deficiencies in all cases, with SmSn2 (space group Cmmm, ZrGa2 structure type, Pearson symbol oC12, figure 1b) and GdSn2 (space group Cmcm, ZrSi2 structure type, Pearson symbol oC12, figure 1a) being completely lithium-free. The structure refinements also uncovered positional disorder on the Sn site neighboring the vacancies. The Sn-disorder and the Li-deficiency correlate, and vary monotonically with the decreased size of the rare-earth atoms in the order RE = La�Nd. The SmSn2 and GdSn2 structures are devoid of any disorder.

RELiSn2 or RELixSn2 (RE = La�Nd, Sm, and Gd; 0 = x < 1): Synthesis and crystal chemistry

247th National Meeting (2014)

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