Temperature Dependence of Integrated Intensities of Vibrational Bands in M2GeF6 IR-Absorption Spectra

The paper presents experimental results of studies on the temperature dependence of integrated intensities of vibrational bands corresponding to ₃(GeF ₆) in M₂GeF₆ IR-spectra. It is shown that unlike Na₂GeF₆, Rb₂GaF₆, and Cs₂GeF₆, where the dependence of intensity on temperature is monotonous, in the case of K₂GeF₆ there exist anomalous temperature ranges of 220-240 and 150-170 K, where the intensity of a band, corresponding to ₃(GeF^2- ₆) changes abruptly. The study of heat evaluation, heat capacity, unit cell parameters, and intensities of selective reflexes in K₂GeF₆ X-ray diffraction patterns indicates the presence in this compound, as distinguished from others in the seris considerod, of phase transitions of the first order. On the basis of IB, ¹⁹F NNR, X-rat and calorimetric data, a possible mechanism of polymorphic transformation is discussed.