Relativistic MulticonfigurationalAb InitioCalculation of Uranyl 3d4f Resonant Inelastic X-ray Scattering

Abstract

We applied relativistic multiconfigurational all-electron ab initio calculations including the spin–orbit interaction to calculate the 3d4f resonant inelastic X-ray scattering (RIXS) map (3d 3/2 → 5f 5/2 U M 4 absorption edge and 4f 5/2 → 3d 3/2 U M β emission) of uranyl (UO 2 2+ ). The calculated data are in excellent agreement with experimental results and allow a detailed understanding of the observed features and an unambiguous assignment of all involved intermediate and final states. The energies corresponding to the maxima of the resonant emission and the non-resonant (normal) emission were determined with high accuracy, and the corresponding X-ray absorption near edge structure spectra extracted at these two positions were simulated and agree well with the measured data. With the high quality of our theoretical data, we show that the cause of the splitting of the three main peaks in emission is due to the fine structure splitting of the 4f orbitals induced through the trans di-oxo bonds in uranyl and that we are able to obtain direct information about the energy differences between the 5f and 4f orbitals: Δ5f δ/ϕ – 4f δ/ϕ, Δ5f π* – 4f π, and Δ5f σ* – 4f σ from the 3d4f RIXS map. RIXS maps contain a wealth of information, and ab initio calculations facilitate an understanding of their complex structure in a clear and transparent way. With these calculations, we show that the multiconfigurational protocol, which is nowadays applied as a standard tool to study the X-ray spectra of transition metal complexes, can be extended to the calculation of RIXS maps of systems containing actinides.

The mechanism of Fe induced bond stability of uranyl(v)

“…The An M 4,5 edge HR-XANES are the only experimental techniques allowing to measure for all actinyls(V)/(VI) the energy shis between the d/ f and p* (in some cases) and d/f and s* orbitals from one spectrum without interference with transitions to other orbitals. 17,50,56,59 These orbitals manifest as three identiable peaks in HR-XANES spectra of actinyls, commonly referred to as A (d/f), B (p*) and C (s*) peaks (cf. Fig.…”

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

“…In Table , we present the peak positions and splitting of the U M 4 -edge spectra obtained from experiments by Vitova et al and predicted by molecular ab initio calculations (Sergentu et al, Polly et al, and this work) as well as ab initio finite-difference calculations by Amidani et al using the FDMNES code. , …”

“…As mentioned above, the core spectra of the bare uranyl ion were not only investigated by Polly et al but also by Sergentu et al The embedded uranyl model (UO 2 2+ @Cl 4 4– ), on the other hand, has only been previously investigated for the valence excited state and shown to yield a rather good description of the low-lying states of UO 2 Cl 4 2– in Cs 2 UO 2 Cl 4 .…”

“…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.…”