Ab initio calculations of F-19 NMR chemical shielding for alkali-metal fluorides

[M6F](5+) clusters were chosen to calculate the F-19 NMR chemical shielding for solid state alkali-metal fluorides MF (M = Li, Na, K, Rb) using gauge- independent atomic orbitals (GIAO) at Hartree-Fock (HF) and density functio nal theory (DFT) levels, respectively. The results agree with those measure d experimentally, in particular when the relative deviations within the sam e series are considered. Our results reveal that the variation of chemical shielding from LiF to RbF correlates well with a combined effect from the l attice factor R-2 and the valency factor Q(+)Q(-). (C) 1999 Elsevier Scienc e B.V. All rights reserved.