Origin of the D line in the Raman spectrum of graphite: A study based on Raman frequencies and intensities of polycyclic aromatic hydrocarbon molecules

A common valence force field for polycyclic aromatic hydrocarbons (PAHs) an d graphite has been used in order to explain their Raman spectra from a uni fied viewpoint. On this basis the correlation observed between experimental spectra has been explained and rationalized. Quantum chemical density func tional theory calculations of Raman intensities of small PAHs have been als o performed, supporting the conclusions obtained from the dynamical analysi s. The results obtained are useful for the characterization of materials co ntaining graphitic domains and provide some new insight on the nature of th e D peak in disordered graphite. (C) 2001 American Institute of Physics.