A New Superstructure for the BaAl4-Structure Type: An Experimental and Theoretical Study of La2NiAl7
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Abstract
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.
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Reprinted (adapted) with permission from Chem. Mater., 2005, 17 (14), pp 3661–3667. Copyright 2005 American Chemical Society.