Local site symmetry and electronic structure of trialuminide and related intermetallic alloys probed by solid-state NMR

Intermetallic aluminide alloys with the L1₂, DO₂₂, DO₂₃, and Al₂Ti crystal structures have been examined by NMR using the ²⁷Al resonance to investigate how changes in crystal structure affect the local environment as indicated by hyperfine interactions at the atomic nucleus. All nonequivalent Al sites have been clearly resolved. Further, the environment of the transition metal component in each intermetallic crystal structure has been investigated using the ⁴⁵Sc resonance in the L1₂ structure of Al₃Sc, the ⁴⁹Ti resonance in the DO₂₂ structure of Al₃Ti, and in Al₂Ti, the ⁵¹V resonance in the DO₂₂ structure of Al₃V and the ⁹¹Zr resonance in the DO₂₃ structure of Al₃Zr. Using a combination of static and magic-angle spinning Fourier transform NMR, and static field sweep spectroscopy, the isotropic Knight shifts (Kᵢₛₒ) and the nuclear quadrupole coupling constants (Cq) have been determined for all nuclei and all sites. In some cases the ²⁷Al axial Knight shift (Kₐₓ) has been obtained. In the trialuminides each Al site located by NMR has been identified with the corresponding site in the unit cell of the crystal structure.