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

Intermetallic aluminide alloys with the L1(2), DO22, DO23, and Al2Ti crystal structures have been examined by NMR using the Al-27 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 Sc-45 resonance in the L1(2) structure of Al3Sc, the Ti-49 resonance in the DO22 structure of Al3Ti, and in Al2Ti, the V-51 resonance in the DO22 structure of Al3V and the Zr-91 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 (K-iso) and the nuclear quadrupole coupling constants (C-q) have been determined for all nuclei and all sites. In some cases the Al-27 axial Knight shift (K-ax) 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.