Theory of X-ray cross correlation and local symmetry

Some readers might remember the news article, "A new technique with coherent X-rays to determine non-crystalline structures", in X-ray Spectrometry, Vol. 38, No.5 (2009). The technique called X-ray cross correlation analysis (XCCA) is an extension of X-ray photon correlation spectroscopy, and is promising with respect to solving the atomic-scale structures of complicated disordered systems, which have for many years presented difficulties in terms of reaching a clear understanding of the structures. Recently, Dr. M. Altarelli (European X-ray Free-Electron Laser Facility, Hamburg, Germany) and his colleagues published a paper on the theoretical treatment of XCCA. They gave a general theory for the cross correlation function, and tried to interpret the experimental XCCA results for colloidal glass. The authors plan further publications to present the results of various simulations as well. For more information, see the paper, "X-ray cross-correlation analysis and local symmetries of disordered systems: General theory", M. Altarelli et al., Phys. Rev. B82, 104207 (2010).