Self-consistent calculation of the phonon-libron spectrum in α-N2

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Abstract
The temperature dependence of the librational and translational lattice modes in α nitrogen is calculated on the basis of two approximate treatments. The random phase approximation is shown to be unsatisfactory in predicting the temperature dependence of the librational frequencies. The self‐consistent phonon approximation is found to be a definite improvement over the random phase approximation. The first model uses quadrupolar interactions alone, the second an atom‐atom potential. Although the atom‐atom potential is moderately successful in fitting observed properties, the evidence for the necessity of a more complete potential, containing quadrupolar as well as short range and long range anisotropic terms, is discussed.