A New Superstructure for the BaAl4-Structure Type: An Experimental and Theoretical Study of La2NiAl7
A new ternary aluminide, La2NiAl7, has been synthesized from the elements in sealed silica tubes. The crystal structure of La2NiAl7 was determined by single-crystal X-ray diffraction and crystallizes in the tetragonal space group I4mm (No. 123) with Z = 4 and lattice parameters a = 6.221(3) and c = 21.403(2) Å. Refinement based on F02 yielded R1 = 0.0313 and wR2 = 0.0392 [I > 2σ(I)]. It is a new structure type, which belongs to the family of BaAl4-related structures. The La2NiAl7 structure corresponds to a 3D superstructure (√2a × √2b × 2c) of the BaAl4-structure type, whereas La3Al11 is only a 1D superstructure (3a × b × c). Tight-binding band structure calculations using the density functional theory have been carried out to understand the structural stability of La2NiAl7 as well as La3Al11.
Reprinted (adapted) with permission from Chem. Mater., 2005, 17 (14), pp 3661–3667. Copyright 2005 American Chemical Society.