Yb₂Al₁₅Pt₆ - the most ordered variety of the Sc_1.2Fe₄Si_9.8 aristotype

Chem. Met. Alloys 7 (2014) 85-99

https://doi.org/10.30970/cma7.0276

Yurii Prots, Micha Deppe, Raul Cardoso-Gil, Antonio Cervellino, Alim Ormeci, Christoph Geibel, Yuri Grin

The title compound was synthesized by reaction of the elemental components in a corundum crucible at 1450 ºC, and subsequent crystal growth using the Bridgman technique. The crystal structure of Yb₂Al₁₅Pt₆ was determined from X-ray single crystal diffraction data: space group Cmcm, Pearson symbol oS92, a = 12.7969(1) Å, b = 7.38813(7) Å, c = 16.3605(2) Å, R_F = 0.036 for 1455 observed structure factors and 65 variable parameters. The title compound crystallizes in a new type of structure, which represents an ordered variety of the Sc_1.2Fe₄Si_9.8 aristotype. The structure can be described as an (ABB)₂ stacking of two trigonal layers with compositions Yb₄Al₆ (A) and Pt₆Al₁₂ (B). The layers A are almost planar and consist of ytterbium atoms arranged at the apexes of condensed hexagons centered by triangular Al₃ units. The slabs B may be considered as distorted hexagonal close-packed, similar to three adjacent layers I-Cd-I of the structure type CdI₂ (Al-Pt-Al). The structural particularities of Yb₂Al₁₅Pt₆ are discussed in comparison with the related structures of Y₂Ga₉Co₃, Tb₂Ge₃Pt₉, Yb₂Ga₉Pd₃ and Er₄Al₂₄Pt₉. A real-space analysis of the chemical bonding with the electron-localizability approach showed that the crystal structure of Yb₂Al₁₅Pt₆ consists of an anionic Al-Pt framework, with Yb cations embedded in cavities. The Al-Pt interactions within the framework are covalent polar, whereas ionic bonding is observed between ytterbium and the framework.

Electron localizability indicator for Yb₂Al₁₅Pt₆.

Keywords

Ytterbium / Platinum / Aluminum / Crystal structure / Intermetallic compound