Eleven new compounds in the RE–Cd–Ge systems (RE=Pr, Nd, Sm, Gd–Yb; Y): Crystal chemistry of the RE2CdGe2 series

A large new family of rare-earth metal–cadmium–germanides RE2CdGe2 (RE=Y, Pr, Nd, Sm, Gd–Yb) has been synthesized and structurally characterized. All eleven structures have been established from single-crystal X-ray diffraction data and have been found to belong to the tetragonal Mo2FeB2 structure type (ordered ternary variant of the U3Si2 structure type—space group P4/mbm (No. 127), Z=2; Pearson symbol tP10). The structural variations among the three series of isostructural RE2MgGe2, RE2InGe2, and RE2CdGe2 compounds are discussed, as well as the crystal chemistry changes as a function of the decreasing size of the rare-earth metals (lattice constants a=7.176(2)–7.4589(12) Å and c=4.1273(14)–4.4356(13) Å). The experimental results have been complemented by tight-binding linear muffin-tin orbital (TB–LMTO) electronic structure calculations. - Graphical abstract: More than 300 compounds have been reported to crystallize with the tetragonal U3Si2 structure type, or the Mo2FeB2 structure type, which is its ordered ternary variant. Among them, there are several large RE2CdX2 classes, where the X-elements are typically late transition metals such as Cu, Ni, Au, Pd, Pt, and Rh. The new RE2CdGe2 phases (RE=Y, Pr, Nd, Sm, Gd–Yb) increase the diversity and represent the first cadmium germanides. Highlights: ► RE2CdGe2 (RE=Y, Pr, Nd, Sm, Gd–Yb) are new ternary germanides. ► Their structures can be recognized as a 1:1 intergrowth of CsCl- and AlB2-like slabs. ► The Ge atoms are covalently bound into Ge2 dumbbells. ► Almost all RE2CdGe2 phases are the first structurally characterized phases in the respective ternary RE–Cd–Ge systems.