C-13 NMR ORBITAL SHIFT CALCULATION IN GRAPHITE-INTERCALATION COMPOUNDS

As suggested by previous results, we show that the conventional analys is of the results of C-13 NMR line shifts used for metals do not apply in GICs: an orbital contribution to the shift must be taken into acco unt, To evaluate quantitatively this contribution, we apply a recently developed formalism for orbital shifts in crystals to the case of fir st and second stage GICs (for B // c), in the independent subsystem ap proximation. It is shown chat the sign of the orbital contribution is different for donor and acceptor compounds but its magnitude is almost independent of the charge transfer amplitude. For second stages, the calculation predicts a splitting of the lines though dipolar contribut ion does not These results explain the experimental data