Combining real-space data analysis of HEXS and XAS to determine the structure of amorphous colloids

Structure analyses of amorphous colloids suffer from absence of periodic structural order and restrict the analytical techniques to near-order sensitive ones like real-space analysis of high-energy X-ray scattering (HEXS) and X-ray absorption spectroscopy (XAS). High-energy X-ray scattering provides precise distances and quantitative electron densities, but comprise scattering contributions from all scattering pairs in the structure whose separation becomes difficult with increasing number of elements involved. EXAFS, in contrast, is an element selective technique and provides exclusively structural information from the direct neighborhood of the absorbing atom, but suffer often from destructive interference effects as soon as the symmetry of the structure becomes low. A combination of these techniques is widely able to overcome their individual restrictions. Basic principles and examples will be discussed in detail.