Yb2Al15Pt6 - the most ordered variety of the Sc1.2Fe4Si9.8 aristotype

 

Chem. Met. Alloys 7 (2014) 85-99

 

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, RF = 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 Sc1.2Fe4Si9.8 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