Enhanced microcomputer operation of X-ray diffractometers and subsequent applications.
Stewart, Neil Sutherland
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The work described within this thesis is mainly concerned with the solution and refinement of the molecular structures of a variety of novel compounds. A number of X-ray and neutron diffractometers have been utilised for the analysis of specific compounds, depending on the nature of the investigation. Each of the instruments represented differing levels of computer automation and instrumentation. A powder diffractometer, representing old technology was interfaced to a microcomputer to enhance the instruments performance. A brief overview is given of the numerical processes involved in the elucidation and refinement of molecular structures from X-ray and neutron diffraction data. Particular attention has been placed on the role of computers to perform these calculations. The operation of the diffractometers employed in this study has been discussed comparing the benefits of each. A detailed report of the techniques used to enhance the low resolution diffractometer and of the experiments performed to highlight the increased performance has been included. Single crystal and powder diffraction studies were made of a wide variety of crystalline materials ranging from steroids to organometallic compounds. The X-ray structures were solved using Direct and Patterson vector methods from experimental data collected on a four circle diffractometer at Aberdeen University. Neutron diffraction experiments, performed at the Rutherford Appleton Laboratory, were commissioned to determine and refine the positions of the hydrogen atoms of two known structures, previously solved by Xray studies. Finally a critical evaluation of current computer automated diffractometers is presented, highlighting the new areas of instrument development.