Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)




Professor J. A. Morrison


The vibrational properties of polytypes of PbI₂ crystals have been studied experimentally by means of the techniques of Raman spectroscopy, X-ray diffraction and low temperature calorimetry. The crystals were prepared by three different methods: gel growth, thermal annealing and growth from the melt.

The Raman spectra are used to determine features of the phonon dispersion curves, in the crystallographic c-direction, that are common to all of the polytypes. The results are correlated with existing information obtained from measurements of Brillouin spectra and inelastic scattering of neutrons.

Both the heat capacity and the thermal conductivity were determined from the calorimetric measurements in the region 0.5

All of the results are analysed within the framework of a 6-parameter force constant model. Bounds are placed on the magnitudes of anharmonic and 2-dimensional contributions to the vibrational properties.

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