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The zero wave vector k=0 lattice vibrational frequencies of solid NH3 are calculated using atom–atom models for the short range intermolecular forces, a point charge model for the electrostatic interactions, and the correct dispersion interaction for large intermolecular separations. Comparison is made with available infrared and Raman data. An estimate is also made of the anharmonic contributions to the librational modes.
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Righini et al. (1978) studied this question.
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