HR: 11:50h
AN: V21E-07    [PDF]
TI: Theoretical study on structural factors correlated with $^{23}$Na NMR parameters
AU: * Tossell, J
EM: Tossell@chem.umd.edu
AF: Dept. of Chem. & Biochem., University of Maryland, College Park, MD 20742 United States
AU: Liu, Y
EM: yunliu@glue.umd.edu
AF: Dept. of Chem. & Biochem., University of Maryland, College Park, MD 20742 United States
AU: Nekvasil, H
EM: hnekvasil@notes.cc.sunysb.edu
AF: Dept.of Geosciences, SUNY at Stony Brook, Stony Brook, NY 11790 United States
AB: Ab initio NMR calculations at the HF/6-311+G(2df,p) GIAO level are performed on many Na-centered clusters with different O-ligands. Several aspects of the relationship between local structure and $^{23}$Na NMR parameters have been carefully investigated. The accuracy of $^{23}$Na NMR calculation is checked by calculating $^{23}$Na NMR shieldings for similar crystalline materials with known experimental shieldings. The largest Na-O distance which can still contribute to the Na shielding is found to be about 3.5 {\AA}. Quantitative contributions to the Na shielding from different individual O-ligands are emphasized in this paper. These contributions are carefully calculated and compared to establish the order of decreasing deshielding as: OH, NBO(Al)$>$Al-O-Si$>$NBO(Si)$>$Al-OH $>$H2O$>$Si-O-Si$>$Si-OH Na-clustering effects from other cations nearby are also found to tremendously increase the shielding of Na. Finally, the relationship between local structure and the Na NMR has been used to explain the Na NMR data for hydrous albite glasses.
DE: 1000 GEOCHEMISTRY (New field, replaces Rock Chemistry)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting