Application of the Tikhonov Regularization Method to the EXAFS analysis of UO2(H2AsO4)2 x H2O


Application of the Tikhonov Regularization Method to the EXAFS analysis of UO2(H2AsO4)2 x H2O

Zayarnaya, T.; Reich, T.; Hennig, C.; Funke, H.

We consider the possibility to determine structural parameters from partial pair correlation functions (PCF's) for UO2(H2AsO4)2 x H2O assuming that its crystal structure is unknown. Since UO2(HAsO4) x 4H2O is chemically similar to UO2(H2AsO4)2 x H2O, we wanted to investigate whether the scattering characteristics calculated by FEFF-8 for the uranium hydrogen arsenate with a known crystal structure are transferable for the analysis of the uranium dihydrogen arsenate.
The Tikhonov regularization method was applied to solve the inverse ill-posed problem of finding up to three partial PCF's from one EXAFS spectrum of UO2(H2AsO4)2 x H2O. From the U L3-edge EXAFS spectrum, we determined the U-U, U-As, and U-O PCF's. The As-As, As-U, and As-O PCF's were received from the As K-edge EXAFS spectrum. The interatomic distances obtained for the first and in several cases also for the second coordination shell of all pairs are in agreement with recently published crystallographic values. This demonstrates that the Tikhonov regularization method is a powerful tool for the structural analysis of samples for which only chemical information (oxidation state, elemental composition, type of ligands) is known.

* Corresponding author: zayarnaya@imp.uran.ru

  • Lecture (Conference)
    Actinide-XAS-2000 Workshop Proceedings, Grenoble, Sept. 10.-12.2000

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Publ.-Id: 3711