Quantum chemical calculations of the structure and Debye-Waller factors of actinide complexes; a comparison with experimental EXAFS data.
Résumé
Quantum chemical calculations provide information on the local structure of aqueous metal complexes and on the occurrence of bond isomers and their thermodynamic stability. This type of information provides models that are essential for the proper analysis of the “two-dimensional” EXAFS data. In addition, these methods enable the calculation of Debye-Waller factors for single and multiple scattering pathways, from a full ab initio normal mode analysis. The latter values can then be used as fixed parameters in the EXAFS fitting procedure, thus reducing the number of parameters to be varied and improving the chemical conclusions drawn from the experimental data. We use examples from the chemistry of uranyl(VI) to illustrate how ab initio data can be used to reveal the three-dimensional structure of complexes in solution and discuss the agreement between calculated and EXAFS fitted Debye-Waller factors.