Experimental and theoretical studies of some inorganic single-crystals.
thesisposted on 19.11.2015, 08:47 by David Charles. Stevens
Research reported herein embraces two distinct aspects of vibrational spectroscopy. The first is that of VIBRATIONAL ANALYSIS. An introduction to the aims and methodology, and some of the problems and limitations of this discipline is provided. Results are reported for two systems, both complex and many-atom. Benzenetricarbonylchromium and its deuteriated analogue are investigated. The effects of ligation on the force constants of the benzene ring are evaluated and discussed; the normal modes are described; and the effects of kinematic coupling critically examined. An approximate vibrational model for CsNiC13 is presented, using a simple valence force field. Frequencies for both 'active' and 'inactive' modes are calculated, as are potential energy distributions and cartesian displacement coordinates. Parallel analyses are also presented for the related compounds CsNiF3, CsNiBr3, CSCoC13 and RbNiC13, and comparisons made. The second aspect is that of SINGLE-CRYSTAL VIBRATIONAL SPECTROSCOPY. An introduction is provided to the relevant theory and to various technical aspects, in particular infrared reflectance. Five compounds are examined. All the fundamental modes of tetragonal Pb0 are reported, and all but one assigned unequivocally by single-crystal techniques. The behaviour of the Eu reflectance band with decrease in temperature is thoroughly investigated and accounted for. Reflectance spectra are analysed and the relevant optical parameters computed. The first complete Raman spectrum, and single-crystal i.r. reflectance data are reported for orthorhombic Pb0, and an assignment proposed using a line-group approach. The unusual dielectric constant of the material is accounted for. Polarised single-crystal reflectance spectra are reported for methylammonium and propylammonium tetrachloromanganate (II) over the temperature range 295 to 50 K. Single-crystal Raman spectra over a similar range are also described. The main features of the spectra, particularly for the ambient temperature phases, are assigned with the aid of a factor group analysis. Single-crystal i.r. data for the planar molecule bis(dimethylglyoximato)nickel(II) are reported, and the out-of-plane skeletal modes located and assigned by direct experiment. Further necessary experimentation is detailed. Finally, accounts are provided of the computational methods used in the research, including a listing of a 'harmonic' oscillator programme developed by the author.