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

The new ternary compounds La ₁₅ Ni ₁₃ Bi ₅ and La ₉ Ni ₈ Sn ₅ 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: La ₁₅ Ni ₁₃ Bi ₅ crystallizes in the hexagonal space group P 62 m [ hP 33, a = 14.995(3), c = 4.3421(10) Å, V = 845.5(4) Å ³ , Z = 1] and La ₉ Ni ₈ Sn ₅ in P 6 ₃ / m [ hP 88, a = 23.870(15), c = 4.433(3) Å, V = 2187(3) Å ³ , Z = 4]. The crystal structures of both compounds are characterized by hexagonal honeycomb-based motifs formed by Ni and Sn that extend along the c 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 p -element, which supports the formation of the polyanionic Ni- p -element network. DFT calculations suggest paramagnetic-like behavior for both compounds, which was confirmed by magnetic measurements.