In the previous Chapters we have discussed the vibrational properties of molecular crystals in terms of harmonic motions of the molecules, taking into account only quadratic terms of the crystal potential. This “harmonic” approximation corresponds to the assumption that the vibrational excitation of the crystal can be rigorously separated into a set of independent and non-interacting phonons, each having an infinite lifetime.
KeywordsPhonon Frequency Molecular Crystal Intermolecular Potential Phonon Line Crystal Potential
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