A Model for the Lattice Dynamics of Naphthalene and Anthracene

Abstract The lattice dynamics of a model for naphthalene and anthracene is presented. Intermolecular forces of the ‘6‐exp’ interatomic type are assumed, and dispersion curves are calculated. It is stressed that the Raman modes do not involve rotations about the principal inertia axes. Frequency distributions, Debye temperatures and Debye‐Waller factors are calculated, and the validity of using the last to estimate Raman frequencies is assessed. The agreement with experiment is good, except perhaps, for the elastic constants. Finally the thermal diffuse X‐ray scattering is calculated and compared with experiment. The low resolution results agree both with experiment and with the ‘difference Fourier transform’ theory. The high resolution calculation, however, explains the discrepancies between experiment and the earlier theory.

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