Structural studies of titanyl and zirconyl sulphate hydrates

Abstract

The aim of this thesis was to use a combination of computer simulations and experimental methods to gain insight into the unknown structure of the material titanyl sulphate dihydrate, TiOSO4*2H2O.Samples of TiOSO4*2H2O, along with TiOSO4*H2O, were produced and analysed using X-ray and neutron diffraction at both laboratory and synchrotron facilities. Both ex-situ and in-situ experiments were performed in order to analyse both the structure and growth of the crystals. The diffraction data resulting from these experiments was then used in various structure determination programs. A unit cell was able to be determined from the synchrotron X-ray diffraction patterns, and the first neutron diffraction pattern of a TiOSO4*2D2O sample was produced. In-situ synchrotron X-ray diffraction studies showed that the formation of the crystals followed a single step process, and indicated the possibility of meta-stable phases being present in the sample.In parallel with the experimental studies, computer modelling was used to develop and create candidate TiOSO4*2H2O structures. Initially both forcefield and first principles techniques were validated against a series of test cases. These included the first such calculations for the TiOSO4 and TiOSO4*H2O structures. The candidate structures of TiOSO4*2H2O thus produced were then used as input into the structural determination step.Structure determination was attempted with multiple approaches, using the determined unit cell and a variety of space group settings. Despite a thorough treatment and validation of the method using the diffraction data and known structure of TiOSO4*H2O, the structure was unable to be solved. However, structural motifs consistent with a layered, needle-like morphology, as observed in experimental studies, were commonly found to be present in solutions offered by these approaches. Future use of techniques such as the substitution of isotopic titanium in neutron diffraction may provide enough information to more accurately determine atomic positions.