X-ray absorption spectroscopy
X-ray absorption spectroscopy X-ray absorption fine structure (XAFS) is a powerful spectroscopic technique that generally requires application of synchrotron X-ray radiation. It provides information on the physical and chemical properties of matter at the atomic scale. XAFS is an element-specific technique which allows to selectively probe the local structure around the absorbing atom. XAFS can be applied to the materials in both solid, liquid and even gas phase. Unlike X-ray diffraction, the method does not require long range order in the samples and can be used to study the structure of nanomaterials, small molecules, enzymes and proteins, and many others. The extended X-ray absorption fine structure (EXAFS) provides the radial distribution function, so interatomic distances and coordination numbers can be extracted. At the same time X-ray absorption near-edge structure (XANES) is also sensitive to the oxidation state and bond angles.

Our group has a wide experience in experimental applications and theoretical analysis of X-ray absorption data. The members of our team have performed a great number of experiments at the world leading synchrotron radiation sources, such as ESRF and Soleil (France), DORIS, ANKA, DESY and BESSY (Germany), SLS (Switzerland), MAX-IV (Sweden), Kurchatov Institute (Russia). Moreover, we have a laboratory X-ray absorption spectrometer manufactured by Rigaku, which has no analogues in Russia and Europe.

For theoretical analysis of EXAFS we are using standard Fourier-analysis (software: Artemis, Wiper). The analysis of XANES and theoretical calculation of spectra is a complicated field, in which our group have long traditions. In particular, We have developed a FitIt code which allows to perform the fitting of experimental spectra using multidimensional interpolation approach [1,2]. Recently, we made a significant improvement in the computational performance (up to 40 times speedup!) of the famous FDMNES code for XANES calculation [3].

[1] G. Smolentsev, A. Soldatov. Quantitative local structure refinement from XANES: multidimensional interpolation approach. Journal of Synchrotron Radiation 2006, 13, 19-29
[2] G. Smolentsev and A.V. Soldatov. FitIt: new software to extract structural information on the basis of XANES fitting" Computational. Matterial Science 2007, 39, 569–574
[3] S. Guda et al. Optimized Finite Difference Method for the Full-Potential XANES Simulations: Application to Molecular Adsorption Geometries in MOFs and Metal−Ligand Intersystem Crossing Transients. Journal of Chemical Theory and Computation 2015, 11, 4512−4521

Members:  Carlo Lamberti / Alexander Guda / Alexander Soldatov / Aram Bugaev / Kirill Lomachenko / Antonina Kravtsova / Mikhail Soldatov
Collaborations:  University of Turin / Paul Sherrer Institute / Kurchatov Institute / ESRF / DESY / European XFEL / Karlsruhe Institute of Technology