Mapping the Hidden Landscape of Ln-Rich Platinides

Despite extensive explorations, lanthanide-platinum (Ln-Pt) systems showed surprising differences with respect to reported compounds, particularly in the Ln-rich area. A re-examination of the corresponding systems revealed several hidden series with light Ln up to Gd, namely Ln2Pt (Pearson symbol oP12, Co2Si structure type, space group Pnma), Ln5Pt3 (Pearson symbol tP32, Pu5Rh3 structure type, space group P4/ncc or Pearson symbol hP16, Mn5Si3 structure type, space group P63/mcm), Ln3Pt2 (Pearson symbol hR45, Er3Ni2 structure type, space group R3̅) and Ln3Pt2-x (Pearson symbol tI80-16x, Pr3Pt2-x structure type, space group I4/mcm). All crystal structure and phase analyses have been performed by means of single-crystal and powder X-ray diffraction. A comprehensive comparative analysis of the related binary systems in the range of 33-40 at. % of the transition metal has been performed. Notably, none of the series is identical to any other in this work or other Ln-transition metal systems. DFT-based electronic structure calculations were employed to examine the structural preferences of the selected series and to investigate possible polymorphic transformations.