Rigorous theory for chemical shifts in crystal: Application to graphite

Abstract
A rigorous theory for chemical shifts in crystal is developed. In this formalism, it is clearly seen that the shielding tensor is divided into a demagnetizing term and a microscopic term. The former is caused by the demagnetizing field and is proportional to the bulk susceptibility. The latter is caused by a periodic current, which is, in the atomic limit, reduced to the ordinary expression for the shielding tensor by Ramsey. A new expression for the shielding tensor for the on-site approximation is derived based on the rigorous theory. The present theory is applied to graphite, and it is shown that the temperature-dependent part of the observed shift is due to the demagnetizing term.

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