SPECTROSCOPIC INVESTIGATION OF THE CRYSTAL STRUCTURE OF THE BINARY SYSTEM $LiIO_{3}$--$HIO_{3}$
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Date
1997
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Ohio State University
Abstract
The lattice dynamics of the pseudo-binary system $LiIO_{3} - HIO_{3}$ has been investigated by means of the IR and Raman spectroscopies and the NQR technique. The spectral changes, observed in the $2600 - 400 cm^{-1}$ region, indicate the formation of variable ``intermolecular” hydrogen bonds $O-H \cdots O$ in the system between the quasi molecular halogenate groups $IO_{3}^{-}, HIO_{3}$ and $H(IO_{3})_{2}^{-}$. By the analysis of low-frequency Raman spectra of the mixed crystals $Li_{1-x} H_{x} IO_{3}$ with varying the concentration {x} in the range from 0 to 1, the critical {x} values of $HIO_{3}$ content were evaluated at which the hydrogen bonds of different strength are formed and the different crystal structure of the binary system is observed. Thus for the concentration range 0-0.22 the IR absorption spectra show wide and weak O-H stretching bands. That concentration range corresponds to a-modification $LiIO_{3}$ crystal doped by protons ($C_{6}^{6}$ space group). Within the intermediate concentration range $0.06 < x < 0.22$ two separate crystals $\alpha-LiIO_{3}$ and $2LiIO_{3} \cdot HIO_{3}$ (with unknown crystal structure) exist as it follows form the NQR data. For concentrations x$ > 0.35$ the vibrational spectra of the system correspond to Li-doped orthorhombic $\alpha-HIO_{3}$ crystal. From the NQR and Raman data the amorphous (``glass”) phase was detected in the concentration range 0.22-0.35. Our results help to solve some contradictions concerning the binary system structure obtained by different experimental methods.
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Author Institution: Institute of Physics, National Academy of Sciences of Ukraine