Elucidating cation–cation interactions in neptunyl dications using multi-referenceab initiotheory

Abstract

Understanding the binding mechanism in neptunyl clusters formed due to cation-cation interactions is of crucial importance in nuclear waste reprocessing and related areas of research. Since experimental manipulations with such species are often rather limited, we have to rely on quantumchemical predictions of their electronic structures and spectroscopic parameters. In this work, we present a state-of-the-art quantum chemical study of the T-shaped and diamond-shaped neptunyl(V) and neptunyl(VI) dimers. Specifically, we scrutinize their molecular structures, (implicit and explicit) solvation effects, the interplay of static and dynamical correlation, and the influence of spin-orbit coupling on the ground state and lowest-lying excited states for different total spin states and total charges of the neptunyl dications. Furthermore, we use the picture of interacting orbitals (quantum entanglement and correlation analysis) to identify strongly correlated orbitals in the cation-cation complexes that should be included in complete active space calculations. Most importantly, our study highlights the complex interplay of correlation effects and relativistic corrections in the description of the ground and lowest-lying excited states of neptunyl dications.

Use of vibrational spectroscopy to identify the formation of neptunyl–neptunyl interactions: a paired density functional theory and Raman spectroscopy study

“…Previous theoretical studies have investigated AAIs using both DFT and wavefunction based methods. [37][38][39][40][41][42][43] A primary goal in each of these studies was to predict the overall stability of different AAI dimers and understand the unique bonding occurring between the two actinyl species through investigations of molecular orbitals and electron/charge transfer. Due to the unique vibrational features in IR and Raman spectroscopy that arise from these interactions in both solution and the solid-state, we use DFT to elucidate the emergence of these new vibrational modes from additional neptunyl polymerization.…”

Destruction of the Uranyl Moiety in a U(V) “Cation–Cation” Interaction

“…It should be noted that there is no mechanistic evidence that the eliminated O 2 is the bridging peroxide; only the net reaction is definitively established. Simplified structures for CCIs between two U­(V) moieties are in Scheme . Structures a and b are typical condensed-phase CCIs. , Structure c is a cis -dioxido uranyl configuration as has been alleged to form in a coordination polymer, a claim that has been disputed . In structure d the uranyl moieties have been disrupted to such an extent, actually destroyed, that a better description is two terminal UO t species linked by two bridging O b atoms.…”

Pythonic Black-box Electronic Structure Tool (PyBEST). An open-source Python platform for electronic structure calculations at the interface between chemistry and physics

“…The orbital-pair mutual information allows us to dissect electron correlation effects into different contributions and (together with the single-orbital entropy) represents a useful tool to define optimal and balanced active spaces. 14,[59][60][61][62][63][64][65] The released version of PyBEST supports an orbital entanglement and correlation analysis for the pCCD and LCC wavefunction models. § ¤ # o r b i t a l e n t a n g l e m e n t module…”