71 Ga and 69 Ga single-crystal NMR spectra of a -Ga 2 O 3 twin have been analyzed in terms of the 71 Ga/ 69 Ga quadrupole coupling and chemical shielding anisotropy (CSA) interactions. Analyses of the magnitudes and orientations of the interaction tensors for the two distinct crystallographic gallium sites in the two twin crystals resulted in accurate values for the parameters describing the quadrupole coupling and CSA tensors. Moreover, it has been possible to determine the actual twin-law of our sample crystal. Along with a recent 71 Ga single-crystal NMR investigation of YGG, this work shows that gallium CSA generally has to be taken into account in addition to the dominant quadrupole coupling interaction.S0002-7863(98)01666-7 CCC: $15.00
The two crystallographically distinct sites in Rb 2 CrO 4 are characterized in terms of their 87 Rb quadrupole coupling and chemical shielding anisotropy (CSA) interactions employing 87 Rb single-crystal NMR. Accurate values for the quadrupole coupling and CSA parameters are reported for both rubidium sites along with the direction cosines describing the orientation of the tensors for the NMR interactions with respect to the Rb 2 -CrO 4 crystal frame. The parameters for site 1 represent the first accurate investigation of this site, while the parameters for site 2 compare excellently with those previously reported. Some remarkable similarities are observed between the present parameters for Rb 2 CrO 4 and the 133 Cs parameters determined from recent magicangle spinning and single-crystal 133 Cs NMR studies for the isomorphous Cs 2 CrO 4 .
The capability of single-crystal NMR to extract crystal structure information is demonstrated by a 27 Al single-crystal NMR study of the garnet Y 3 Al 5 O 12 (YAG). By rotation of a YAG single crystal about three perpendicular axes 93 27 Al spectra have been acquired, resulting in the observation of 3132 resonance frequencies. These have been assigned to three tetrahedral and four octahedral aluminum sites. A thorough analysis of the magnitudes and relative orientations of the quadrupole coupling tensors for these seven aluminum sites indicates the presence of a combination of symmetry elements that is unique to cubic crystal structures. Upper limits for the magnitudes of the anisotropic chemical shielding interaction are also determined for the seven aluminum sites and show that the geometrical arrangements of oxygen ions in the first coordination sphere of all aluminum sites must be nearly regular tetrahedra and octahedra, respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.