Graphite and graphitic compounds: vibrational spectra from oligomers to real materials

An empirical valence force-field has been obtained for an ideal two-dimensi onal crystal of graphite. This force field is the generalization to the inf inite case of the force field developed by Ohno (in K. Ohno, J. Chem. Phys. 95 (1991) 5524; K. Ohno, J. Mol. Spectrosc. 72 (1978) 238) for simple Poly cyclic Aromatic Hydrocarbons (PAH). Based on classical dynamical calculatio ns we have clarified the origin of the Raman bands observed in PAH and have rationalized their correlation with the Raman features observed in graphit ic materials with different degree of purity and crystalline order. (C) 199 9 Elsevier Science B.V. All rights reserved.