How to build a homologous series from parent compounds: Synthesis, crystal, and electronic structures of La2Ni2Al·n(LaNi2Al)

• Published in: Journal of solid state chemistry 2024-04, Vol.332, p.124593, Article 124593
• Main Authors: Tursina, Anna I., Nesterenko, Sergey N., Chernyshev, Ilja V., Kuznetsov, Alexey N.
• Format: Article
• Language: English
• Subjects: Bonding; Crystal chemistry; Density functional theory; Intermetallics; X-ray diffraction
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2024.124593

Rich in ternary intermetallics, La–Ni–Al system surprises again with the discovery of a new series of intergrowth compounds. Crystal structures of La4Ni6+xAl3-x (x = 0.3) and La5Ni8+xAl4-x (x = 0.34) were established from single-crystal diffraction data. Crystallizing within monoclinic space group C2/m with Z = 2, very close a and b cell dimensions and similar sets of atomic positions, new compounds represent their own structure types. The crystal structure of LaNi2Al was determined from powder X-ray data – it adopts a SrCu2Ga-type structure, space group R3‾m, Z = 3. Combinations of the fragments of LaNi2Al and La2Ni2Al structures generate a new homologous series of intergrowth structures – La2Ni2Al·n(LaNi2Al) (n = 0 ÷ 3, ∞), with La2Ni2Al and LaNi2Al being the parent structures for n = 0 and n = ∞, respectively. The series is built by successive addition of one “LaNi2Al” block to the preceding member beginning with the La2Ni2Al compound as the first one. Coordination environment of each atom sort in the intergrowth structures is essentially identical to that in the parent compounds. Electronic structure calculations predict all compounds to be metallic and show a pattern of multi-center bonding between constituent atoms. Energies of formation of the members of the series are discussed based on the DFT calculations. [Display omitted] •Four ternary intermetallics in the La–Ni–Al system were synthesized.•La3Ni4Al2, La4Ni6Al3, and La5Ni8Al4 form a homologous family m(La2Ni2Al)·n(LaNi2Al).•La2Ni2Al (n = 0) and LaNi2Al (n = ∞) represent the parent compounds.•Atomic environment in the series is identical to those in the parent compounds.•DFT calculations show the compounds to be metallic with multi-center bonding.