Local Electronic Structure in γ-LiAlO2Studied by Single-Crystal27Al NMR and DFT Calculations.
From single-crystal27Al NMR experiments, the full tensors for both the electrical field gradient (EFG) and the chemical shift (CS) for the aluminum atoms in γ-LiAlO2have been determined. A simultaneous fit of the quadrupolar splittings observed for the four27Al in the unit cell gave the EFG tensor in the crystal frame, from which a quadrupolar coupling constant of χ = CQ= 3.330 ± 0.005 MHz and an asymmetry parameter of ηQ= 0.656 ± 0.002 were derived. The experimentally determined quadrupolar splittings were sufficiently sensitive to quantify small deviations of both rotation axis direction and starting direction by the data fitting routine. For determination of the CS tensor, the evolution of the outer satellite centers over the crystal rotation was tracked, and the contribution of the quadrupolar shift was subtracted according to the previously determined EFG tensor. The resulting CS tensor of27Al yields an isotropic chemical shift of δiso= 81.8 ± 0.25 ppm and an asymmetry parameter of ηCS= 0.532 ± 0.004, in good agreement with the fit of a MAS NMR spectrum acquired at B0= 21.1 T. From both experiments and DFT calculations using the Castep code, we find the eigenvectors of the EFG and CS tensors to be practically colinear.
Department of Chemistry, University of Munich (LMU) Butenandtstr. 5-13, 81377 Munich, Germany.
Thomas
T
Bräuniger
Department of Chemistry, University of Munich (LMU) Butenandtstr. 5-13, 81377 Munich, Germany.
Burkhard
B
Groh
Max-Planck-Institute for Solid-State Research , Heisenbergstr. 1, 70569 Stuttgart, Germany.
Igor L
IL
Moudrakovski
Karlsruhe Institute of Technology , Institute for Applied Materials (IAM), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
Sylvio
S
Indris