Structure and Dynamics of the Uranyl Tricarbonate Complex in Aqueous Solution: Insights from Quantum Mechanical Charge Field Molecular Dynamics

Abstract

This investigation presents the characterization of structural and dynamical properties of uranyl tricarbonate in aqueous solution employing an extended hybrid quantum mechanical/molecular mechanical (QM/MM) approach. It is shown that the inclusion of explicit solvent molecules in the quantum chemical treatment is essential to mimic the complex interaction occurring in an aqueous environment. Thus, in contrast to gas phase cluster calculations on a quantum chemical level proposing a 6-fold coordination of the three carbonates, the QMCF MD simulation proposes a 5-fold coordination. An extensive comparison of the simulation results to structural and dynamical data available in the literature was found to be in excellent agreement. Furthermore, this work is the first theoretical study on a quantum chemical level of theory able to observe the conversion of carbonate (CO₃²⁻) to bicarbonate (HCO₃⁻) in the equatorial coordination sphere of the uranyl ion. From a comparison of the free energy ΔG values for the unprotonated educt [UO₂(CO₃)₃]⁴⁻ and the protonated [UO₂(CO₃)₂(HCO₃)]³⁻, it could be concluded that the reaction equilibrium is strongly shifted toward the product state confirming the benignity for the observed protonation reaction. Structural properties and the three-dimensional arrangement of carbonate ligands were analyzed via pair-, three-body, and angular distributions, the dynamical properties were evaluated by hydrogen-bond correlation functions and vibrational power spectra.

Rational Design of Porous Nanofiber Adsorbent by Blow‐Spinning with Ultrahigh Uranium Recovery Capacity from Seawater

“…The pore size was found to be critical for the uranium adsorption capacity of the adsorbent . Crystal structure analysis of the uranyl species [UO 2 (CO 3 ) 3 ] 4− , which is the dominant form of uranyl in seawater, reveals that it has a diameter of 0.6 nm axially and 1 nm equatorially . The small pore size of PAO might restrict the entrance of [UO 2 (CO 3 ) 3 ] 4− into the cavity in the adsorbent and limit the adsorption capacity of the adsorbent.…”

First-principles molecular dynamics simulation of the Ca2UO2(CO3)3 complex in water

“…[24][25][26][27] Hofer et al examined the structure and dynamics of [UO 2 (CO 3 ) 3 ] 4− in water using quantum mechanical charge field molecular dynamics (QMCF-MD). 24,25 Kerisit et al investigated the structure and dynamics of Ca 2 UO 2 (CO 3 ) 3 in aqueous solution with classical MD simulations based on non-polarizable force fields. 26 Given the highly charged nature of Ca 2+ ions and [UO 2 (CO 3 ) 3 ] 4− , polarization may be important in describing the interaction between Ca 2+ ions and [UO 2 (CO 3 ) 3 ] 4− and between the complex and the water molecules.…”

Optimizing link atom parameters for DNA QM/MM simulations

“…QM/MM-MD [1,4,5,14,15,29,37,43,44] simulations are of ever-growing interest for the investigation of metalion complexes [19,28,30,38,41] and biomolecules [36], such as proteins and ribonucleic acids, because of their methodological flexibility, the capacity to investigate subpicosecond events as well as the possibility to predict interor intramolecular interactions and even chemical reactions. Besides the higher accuracy, the main advantage of hybrid QM/MM-MD to classical MM-MD simulations that 47 Page 2 of 7 computations were performed, utilizing a triple-zeta basis set [12,45].…”