Ordering by cation replacement in the system Na 2- x Li x Ga 7

• Published in: Dalton transactions : an international journal of inorganic chemistry 2024-01, Vol.53 (3), p.908-916
• Main Authors: Yu, Chia-Chi, Prots, Yurii, Ormeci, Alim, Krnel, Mitja, Schmidt, Marcus, Akselrud, Lev, Wagner, Frank R, Grin, Yuri, Baitinger, Michael
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d3dt03628f

Samples of the pseudo-binary system Na Li Ga ( ≤ 1) were synthesized from the elements at 300 °C in sealed Ta ampoules or by the reaction of Na Ga with LiCl. The peritectic formation temperature decreases with increasing Li content from 501(2) °C ( = 0) to 489(2) °C ( = 1). The boundary compositions Na Ga and Na Li Ga crystallize with different structure types related by a group-subgroup relation. While the Na-rich compositions ( ≤ 0.5) represent a substitutional solid solution (space group ), the Li-rich compositions feature an unconventional replacement mechanism in which Li atoms occupying interstitial positions induce vancancies at the Na positions (space group ). The crystal structure of Na Li Ga ( = 8.562(1) Å, = 14.822(2) Å, = 11.454(2) Å; = 8) was determined from X-ray single-crystal diffraction data, and reveals an anionic framework comprising 12-bonded Ga icosahedra and 4-bonded Ga atoms, with alkali-metal atoms occupying channels and cavities. The arrangement of cations makes NaLiGa a new structure type within the MgB Si structure family. Band structure calculations for the composition NaLiGa predict semiconducting behavior consistent with the balance [Na ] [Li ] [(Ga ) ][Ga ] , considering Wade clusters [(12b)Ga ] and Zintl anions [(4b)Ga] . Susceptibility measurements indicate temperature-independent diamagnetic behavior.