A Joint Experimental and Theoretical Study of the Bonding, Energetics, and Excited States of Uranyl Compounds
EMSL Project ID
47951
Abstract
One of the challenges in experimental investigations of actinide complexes is to determine their structures, bonding, and stabilities in solids and solutions. Our recent TRLIF work on U(VI), the single most important element in spent nuclear fuel and nuclear waste and one of the most wide-spread radioactive contaminant at many US DOE sites, has shown that under cryogenic conditions the weak, poorly-resolved fluorescence spectra of many U(VI) species in contaminated natural sediments become intense and highly-resolved, allowing identification of U(VI) species in subsurface sediments. However, such spectral comparisons are solely empirical. No predictive theoretical framework exists to define the dependence of the fluorescence spectrum of a uranyl compound on its chemical or crystal structure. Accurate theoretical predictions of such systems are challenging due to the complicated electron correlation and relativistic (esp. spin-orbit) effects, the large number of valence and semicore electrons in actinide atoms, and the complexity of multiplets of electron configurations of the f-electrons. Very recently, we developed a practical theoretical approach to interpret and simulate the luminescent spectroscopic parameters of actinide compounds using semi-classic time-dependent electronic spectroscopy theory combined with density functional and ab initio methods. Through this attempt, we showed for the first time that one can simulate the vibronically resolved luminescent spectra of actinide systems with reasonable accuracy. Further work has showed that this approach is sufficient for interpreting the luminescent and electronic absorption spectra of actinide compounds.
In this project, we propose to use joint experimental and computational investigations to explore U(VI) excited states and its fluorescence spectroscopic characteristics of a series of uranyl compounds including uranophane [Ca(H3O)2(UO2)2(SiO4)2(H2O)3], liebigite [Ca2(UO2)(CO3)3(H2O)11], meta-autunite {Ca[(UO2)(PO4)]2(H2O)6}, studtite {[(UO2)O2(H2O)2](H2O)2} and schoepite [(UO2)8O2(OH)12(H2O)12]. All five minerals present either in uranium contaminated sediments or may form from alteration of nuclear waste in a geological repository. The experimental studies will be focused on high-resolution time-resolved fluorescence, UV-visible absorption and FT-IR/Raman spectroscopy studies of the selected uranyl compounds. Computational modeling of structures, energetics, vibrational (IR and Raman) spectra, and electronic spectroscopic properties of the selected U(VI) model complexes will be performed in parallel using relativistic quantum chemistry and the time-dependent spectroscopic theory. As relativistic effects, especially spin-orbit (SO) coupling, are critical for accurate calculations of the electronic spectra, we will use SO-DFT, SO-TDDFT, CASPT2/SO, and CASSCF/CCSD(T)/SO approaches to determine the geometries and energies of the ground- and excited-states. Our efforts aim at building a predicative model to interpret the absorption and luminescence spectra of uranyl compounds. The following hypotheses will be tested:
i) Symmetric O=U=O vibrational frequency inversely correlates to the binding strength of the equatorial ligand.
ii) The coupling of the electronic and vibrational transitions is molecular symmetry and ligand dependent.
iii) Absorption intensity is strongly affected by spin-orbit coupling.
This integrated high-resolution optical spectroscopy and theoretical investigation will provide understanding of the relationships between structure, bonding, energetics of the ground and excited states and to correlate such molecular-level properties with the spectroscopy observations and predict the interaction, transport and migration behavior of different forms of uranium species in subsurface environment.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2013-10-01
End Date
2015-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members
Related Publications
Biswas S., S. Edwards, Z. Wang, H. Si, L. Leon Vintro, B. Twamley, and P. Kowalski, et al. 2019. "Americium incorporation into studtite: a theoretical and experimental study." Dalton Transactions 48, no. 34:13057-13063. PNNL-SA-143797. doi:10.1039/c9dt02848j
Corbey J.F., B.M. Rapko, Z. Wang, B.K. McNamara, R.G. Surbella, K.L. Pellegrini, and J.M. Schwantes. 2018. "Crystallographic and Spectroscopic Characterization of Americium Complexes Containing the Bis[(phosphino)methyl]pyridine-1-oxide (NOPOPO) Ligand Platform." Inorganic Chemistry 57, no. 4:2278-2287. PNNL-SA-131204. doi:10.1021/acs.inorgchem.7b03154
Gibson JK, H Hu, MJ Van Stipdonk, G Berden, J Oomens, and J Li. 2015. "Infrared Multiphoton Dissociation Spectroscopy of a Gas-Phase Complex of Uranyl and 3?Oxa-Glutaramide: An Extreme Red-Shift of the [O=U=O]2+ Asymmetric Stretch." Journal of Physical Chemistry A 119(14):3366–3374. doi:10.1021/jp512599e
Hu H ,Wei F ,Wang X ,Andrews L S,Li J 2014. "Actinide–Silicon Multiradical Bonding: Infrared Spectra and Electronic Structures of the Si(?-X)AnF3 (An = Th, U; X = H, F) Molecules" Journal of the American Chemical Society 136(4):1427–1437. 10.1021/ja409527u
Hu H, YF Zhao, JR Hammond, EJ Bylaska, E Apra, HJJ van Dam, J Li, N Govind, and K Kowalski. 2015. "Theoretical studies of the global minima and polarizabilities of small lithium clusters." Chemical Physics Letters 644:235-242. doi:10.1016/j.cplett.2015.11.049
Liu JB ,Chen G ,Huang W ,Clark D L,Schwarz WH E,Li J 2017. "Bonding trends across the series of tricarbonato-actinyl anions [(AnO2)(CO3)3]4- (An = U-Cm): the plutonium turn" Dalton Transactions 46(8):2542.
Liu J., G. Chen, W. Huang, D.L. Clark, W.E. Schwarz, and J. Li. 2017. "Bonding trends across the series of tricarbonato-actinyl anions [(AnO2)(CO3)3]4- (An = U-Cm): the plutonium turn." Dalton Transactions 46, no. 8:2542-2550. PNNL-SA-125514. doi:10.1039/C6DT03953G
Li WL, H Hu, T Jian, GV Lopez, J Su, J Li, and LS Wang. 2013. "Probing the electronic structures of low oxidation-state uranium fluoride molecules UFx- (x=2-4) ." Journal of Chemical Physics 139(24):244303-1 to 244303-8. doi:10.1063/1.4851475
Mehta V, F Maillot, Z Wang, JG Catalano, and DE Giammar. 2014. "Effect of Co-solutes on the Products and Solubility of Uranium(VI) Precipitated with Phosphate." Chemical Geology 364:66-75. doi:10.1016/j.chemgeo.2013.12.002
Muller K., H. Foerstendorf, R. Steudtner, S. Tsushima, M. Kumke, G. Lefevre, and J. Rothe, et al. 2019. "Interdisciplinary Round-Robin Test on Molecular Spectroscopy of the U(VI) Acetate System." ACS Omega 4, no. 5:8167-8177. PNNL-SA-143380. doi:10.1021/acsomega.9b00164
Su J, Z Wang, D Pan, and J Li. 2014. "Excited States and Luminescent Properties of UO2F2 and Its Solvated Complexes in Aqueous Solution." Inorganic Chemistry 53(14):7340-7350. doi:10.1021/ic5006852
Wang G, W Um, Z Wang, E Reinoso Maset, NM Washton, KL Mueller, N Perdrial, PA O'Day, and JD Chorover. 2017. "Uranium Release from Acidic Weathered Hanford Sediments: Single-Pass Flow-Through and Column Experiments." Environmental Science & Technology 51(19):11011-11019. doi:10.1021/acs.est.7b03475
Wang Y., N. Wei, T.W. Wietsma, A.H. Bonneville, x. li, M. Li, and Z. Wang. 2018. "Experimental study of drying effects during supercritical CO2 displacement in a pore network." Microfluidics and Nanofluidics 22, no. 9:101. PNNL-SA-137617. doi:10.1007/s10404-018-2122-9