The Solid Solution Sr1−xBaxGa2: Substitutional Disorder and Chemical Bonding Visited by NMR Spectroscopy and Quantum Mechanical Calculations

• Published in: Chemistry : a European journal Vol. 21; no. 40; pp. 13971 - 13982
• Main Authors: Pecher, Oliver, Mausolf, Bernhard, Lamberts, Kevin, Oligschläger, Dirk, Niewieszol (née Merkens), Carina, Englert, Ulli, Haarmann, Frank
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 28.09.2015; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Barium; Boundary conditions; chemical bonding; Chemical bonds; Chemistry; Data processing; Electric fields; Intermetallic phases; Magnetic resonance spectroscopy; Miscibility; NMR spectroscopy; Organic chemistry; Powder; quantum mechanical calculations; Quantum mechanics; Solid solutions; Spectroscopy; Spectrum analysis; Strontium; Substitutes; substitutional disorder; Superlattices; X-ray diffraction
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201501910

Complete miscibility of the intermetallic phases (IPs) SrGa2 and BaGa2 forming the solid solution Sr1−xBaxGa2 is shown by means of X‐ray diffraction, thermoanalytical and metallographic studies. Regarding the distances of Sr/Ba sites versus substitution degree, a model of isolated substitution centres (ISC) for up to 10 % cation substitution is explored to study the influence on the Ga bonding situation. A combined application of NMR spectroscopy and quantum mechanical (QM) calculations proves the electric field gradient (EFG) to be a sensitive measure of different bonding situations. The experimental resolution is boosted by orientation‐dependent NMR on magnetically aligned powder samples, revealing in first approximation two different Ga species in the ISC regimes. EFG calculations using superlattice structures within periodic boundary conditions are in fair agreement with the NMR spectroscopy data and are discussed in detail regarding their application on disordered IPs. Disorderly conduct: Intermetallic phases were investigated by combining solid‐state synthesis with elaborate experimental and theoretical techniques. Synthesis of Sr1‐xBaxGa2 solid solution samples provides crystalline material (see structure). Alignment of the crystallites in the magnetic field combined with NMR spectroscopy experiments and computational modelling prove different Ga bonding situations depending on substitutional disorder of the cations.