Honeycomb Constructs in the La-Ni Intermetallics: Controlling Dimensionality via -Element Substitution.

The new ternary compounds LaNiBi and LaNiSn were obtained by arc melting under argon from appropriate amounts of the elements and subsequent annealing at 800 °C for 2 weeks. Single-crystal X-ray diffraction reveals that they represent two new structure types: LaNiBi crystallizes in the hexagonal space group 62 [33, = 14.995(3), = 4.3421(10) Å, = 845.5(4) Å, = 1] and LaNiSn in 6/ [88, = 23.870(15), = 4.433(3) Å, = 2187(3) Å, = 4]. The crystal structures of both compounds are characterized by hexagonal honeycomb-based motifs formed by Ni and Sn that extend along the axis. The building motif with its three-blade wind turbine shape is reminiscent of the organic molecule triptycene and is unprecedented in extended solids. First-principles calculations have been performed in order to analyze the electronic structure and provide insight into chemical bonding. They reveal significant electron transfer from La to Ni and the respective -element, which supports the formation of the polyanionic Ni--element network. DFT calculations suggest paramagnetic-like behavior for both compounds, which was confirmed by magnetic measurements.