X-ray absorption spectra of f-element complexes: insight from relativistic multiconfigurational wavefunction theory

Abstract

The calculation of X-ray absorption structures with relativistic multiconfiguration ab-initio wavefunction approaches helps elucidating metal-ligand bonding in lanthanide and actinide complexes.

Synthesis and Characterization of a Bridging Cerium(IV) Nitride Complex

“…The Ce natural electron configuration assigned by the calculation is 4f 0.98 5d 1.21 , deviating strongly from the formal 4f 0 5d 0 . The size of the complex and low local symmetry of the Ce centers prohibited L III -edge wave function calculations. , But, the XANES data and computational results are consistent with a formal and spectroscopic oxidation state of purely cerium­(IV) for 3 , implying a bona fide N 3– moiety.…”

Core Excitations of Uranyl in Cs2UO2Cl4 from Relativistic Embedded Damped Response Time-Dependent Density Functional Theory Calculations

“…More recently, orbital relaxation has also been investigated for excitation energies at the U M 4 -edge of bare uranyl using multiconfigurational approaches. 81,83,84 In the latter case, Polly et al 83 evaluated the performance of various active spaces in SO-RASSCF and SO-RASPT2 simulations. Their results to excitation energies at the U M 4edge were found to overestimate experimental values by 12.9 and 17.4 eV at RASSCF and RASPT2 theory levels, respectively.…”

“…It is known to show very strong U–O triple bonds and generally presents a linear O–U–O geometry, with other ligands coordinating with uranium in the equatorial plane, via less strong interactions. The core spectroscopy of uranyl coordination complexes has been investigated with several theoretical methods, such as complete and restricted active space self-consistent field, ,− crystal ligand-field multiplet theory and its variations, ,,,− density functional theory in its different flavors, ,,,− self-consistent real-space multiple scattering, , static exchange approximation, and perturbation theory …”

“…For molecular-based approaches, relativistic correlated many-body approaches − , are among the most accurate approaches that can be used, but their relatively high computational cost makes them difficult to employ for experimentally relevant systems in the condensed phase. In the case of absorption spectroscopy, it has been found that with a suitable choice of density functional approximation (DFA)notably the CAM-B3LYP functionaldensity functional theory (DFT) can provide reliable excitation energies of actinides in the ultraviolet–visible region, ,,− with a recent, very comprehensive work by Konecny et al employing the four-component damped response time-dependent density functional theory (4c-DR-TD-DFT) formalism, indicating that the same holds for the core excited states of uranium complexes.…”

“…The core spectroscopy of uranyl coordination complexes has been investigated with several theoretical methods, such as complete and restricted active space self-consistent field, 50,81−85 crystal ligand-field multiplet theory and its variations, 34,43,80,86−89 density functional theory in its different flavors, 43,47,57,90−93 self-consistent real-space multiple scattering, 42,43 static exchange approximation, 57 and perturbation theory. 57 For molecular-based approaches, relativistic correlated many-body approaches [83][84][85]94 are among the most accurate approaches that can be used, but their relatively high computational cost makes them difficult to employ for experimentally relevant systems in the condensed phase. In the case of absorption spectroscopy, it has been found that with a suitable choice of density functional approximation (DFA)�notably the CAM-B3LYP functional 95 �density functional theory (DFT) can provide reliable excitation energies of actinides in the ultraviolet−visible region, 76,77,96−99 with a recent, very comprehensive work by Konecny et al 93 employing the four-component damped response timedependent density functional theory (4c-DR-TD-DFT) formalism, indicating that the same holds for the core excited states of uranium complexes.…”