Interplay of Intra- and Intermolecular Interactions in Solid Iodine at Low Temperatures: Experimental and Theoretic Spectroscopy Study.

This work is devoted to the discussion of structural changes in crystalline iodine under low temperature studied from experimental and theoretic points of view. Experimental Raman spectra in the temperature range 5-300 K demonstrated unusual behavior of stretching vibration at ∼180 cm-1 with temperature. The data allowed obtaining of ω( T) functions for both external translational and internal stretching modes of I2. It was found that ω( T) trends significantly differ in comparison to typical van der Waals crystal α-S8. The observed anomalies are explained from a theoretic point of view because of the strengthening of intralayer halogen bonding between I2 molecules.