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

[M6F]5+ clusters were chosen to calculate the 19F 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 functional theory (DFT) levels, respectively. The results agree with those measured experimentally, in particular when the relative deviations within the same series are considered. Our results reveal that the variation of chemical shielding from LiF to RbF correlates well with a combined effect from the lattice factor R−2 and the valency factor Q+Q−.