Dynamics of the rutile structure. III. Lattice dynamics, infrared and Raman spectra of SnO2

For Pt. II see abstr. A71824 of 1970. The polarized infrared reflection absorption and laser Raman spectra have been recorded at both 300K and 100K for single crystals of SnO2. The dielectric parameters epsilon ' and epsilon " have been derived and the optically active transverse and longitudinal k=0 phonon frequencies found. The elastic constants and the dispersion curves for phonons propagating along (0,0, xi ) and ( xi , xi ,0) are calculated using a rigid ion model with short range central axially symmetric forces and long range Coulomb forces which gives satisfactory agreement with the experimentally observed frequencies. The principal force constants and the effective charges on the ions are compared with those for other crystals with the rutile structure. The multiphonon infrared absorption is compared with theoretical predictions based on selection rules and the calculated phonon dispersion curves. The hydroxyl ion impurities are shown to be oriented parallel to the crystal's optic axis.