Abstract
The research of the structure of a crystal is always a very popular and important issue. There are manymethods which can be used to study the structure of the crystal such as X-ray diffraction, X-ray absorption, DAFS(Diffraction Anomalous Fine Structure) and EXAFS(Extended X-ray Anomalous Fine Structure). DAFS is an x-ray spectroscopic, structural and crystallographic method whichcombines the benefit of x-ray diffraction and x-ray absorption by measuring the elastic Bragg reflection intensities versus photon energy. However, we cannot calculate the real part of anomalous scattering factor directly. We have to find out the imaginary part of anomalous scattering factor first, then use the KKR relation to calculate the real part of anomalous scattering factor. The main topic of my thesis is the use of MDAFS(Multiple Diffraction Anomalous Fine Structure) to find out the real part of anomalous scattering factor of GaAS directly. This method does not need to go through the complex procedure, KKR transformations, and provide aquick way to analyze the data collected. By the combining the intensity ratios value Rv, both experimental and theoretical based on the dynamical theory, the the real part of anomalous scattering factor can be determined easily from intensity measurement. Furthermore, we can obtain the fine structure, thus leading to the determination of the distances between Ga and its neighboring atoms.