On the structure and twinning of PtAl4

The crystal structure of PtAl4 was determined from synchrotron data (λ = 0.5608 Å) of a twinned crystal. PtAl4 crystallizes in the trigonal space group P3c1 (no. 158). The lattice constants are a = 13.077(1) Å and b = 9.6342(7) Å. The crystal structure represents a new structure type (Pearson symbol hP90) and consists of layers of edge and face sharing Al10-polyhedra, centered by Pt-atoms. The polyhedra layers are stacked along the crystallographic c-axis and are connected by common corners. Two out of 14 Al-positions show positional disorder and occupational deficiencies.