J. Raich, A. Hüller
Apr 15, 1979
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0
Influential Citations
19
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Journal
Journal of Chemical Physics
Abstract
A microscopic model for the intermolecular interactions is applied to discuss the nature of the α–β structural transformation in sodium azide. NaN3 is an example of an ionic molecular crystal where changes in molecular orientations in the crystal lead to anomalous thermoelastic behavior. Sodium azide differs from other molecular crystals with elastic anomalies such as KCN in that the associated change in orientational order at the transition seems to be quite small. The model, a mean field treatment of the coupling of the rotational motions of the N3− ions to the lattice strains, is shown to lead to indirect N3−–N3− interactions mediated by the lattice. The apparent second‐order nature of the transition is examined. Predictions regarding the temperature dependence of the isothermal elastic constants c44 and 1/2(c11−c12) are made.