Title: Quantum-Mechanical Determination of the Incorporation of Pentavalent Plutonium into Carbonate and Sulfate Minerals Authors: Gebarski, Benjamin Becker, Udo Date Coverage: 6/11/2019 Method: Data set was generated using Biovia Materials Studio 6.1 Service Pack 2 as described in the associated journal article. Description: Files are uploaded as crystallographic information files (.cif), the standard text file format for representing crystallographic information. These files contain the optimized molecular models for pentavalent plutonium incorporation reactions into/onto barite, anglesite, celestine, anhydrite, aragonite, and calcite host minerals. License: Attribution 4.0 international (CC BY 4.0) Research Overview: Pentavalent plutonium is the most abundant form of soluble, mobile, and oxidized Pu in natural systems. The incorporation of Pu into environmentally abundant mineral hosts can strongly influence the transport and concentration of contaminants in both aqueous environments and the subsurface. This study determines the incorporation energy (E, H, and G) of (PuO2)+(HSO4)- and (PuO2)+(HCO3)- from solid Pu2O5 and aqueous (PuO2)+ as sources of Pu(V), as well as the adsorption with subsequent surface incorporation, in a step-by-step approach onto/into different sulfate and carbonate minerals using ab initio computational methods. Solid source and sink reaction energies are calculated for carbonate and sulfate mineral hosts as (MCO3)4 + ½(Pu2O5) + (H2CO3) = ½(H2O) + (MCO3)3(PuO2)(HCO3) + (MCO3) for carbonate structures and (MSO4)4 + ½(Pu2O5) + (H2SO4) = ½(H2O) + (MSO4)3(PuO2)(HSO4) + (MSO4) for sulfate structures, where “M” denotes the metal cation being replaced by PuO2+ (M = Ba, Sr, Pb, Ca). For Pu(V) from solid sources, sulfate group host minerals with the largest cations result in the most favorable incorporation energies; for aqueous sources and sinks, this effect is more than compensated by smaller host cations gaining more hydration energy when released. Thus, incorporation favorability using aqueous sources and sinks vs. solids are nearly reversed, with the smallest cationic radii corresponding to the lowest incorporation energy. While previous studies have used a similar methodology for calculating the thermodynamics of incorporation into bulk minerals, what is new in this study is that the method was extended to observe the rate-controlling steps from a species in solution (e.g., PuO2+ and HSO4- or HCO3 ), to their co-adsorbed state on the mineral surface, followed by their co-incorporation (by replacing divalent cations and anions from the surface of the host mineral), and finally being incorporated into the bulk, mimicking the stability of co-precipitated or overgrown plutonyl defects. As the plutonyl ion approaches the surface, a small activation barrier has to be overcome (~0.2 eV), followed by adsorption which is exothermic (~-2.6 eV) with potential subsequent surface incorporation (endothermic ~1.2 eV). Combining these steps results in a surface incorporation of plutonyl that is energetically downhill (~-1.2 eV), which can sequester plutonyl without the addition of any external energy. Keeping the substituted host ions above the incorporation site is more energetically favorable than releasing them, generating a metastable plutonyl overgrowth site where continued growth is more favorable than re-releasing the plutonyl. These findings, with this more process-oriented and environmentally-relevant approach of surface interactions, considering mineral bulk and surfaces, hydration, and enthalpy, entropy, and Gibbs free energy of individual reaction, facilitate the evaluation of incorporation reactions and narrows the list of minerals favorable for the incorporation of actinides to complement (particularly resource-limited) experimental study. In addition, it may serve as a model for future semi-kinetic studies where a full computational treatment of the kinetics is prohibitively computationally expensive. This research was conducted by Benjamin Gebarski and Udo Becker at the University of Michigan-Ann Arbor and was submitted for publication on 6/11/2019. This research was supported by U.S. Department of Energy: Heavy Element Chemistry and Geosciences grant DE-FG02-06ER15783. Methods: Molecular models were generated using Biovia Materials Studio 6.1 Service Pack 2 as described in the associated journal article. File Inventory: 55 separate molecular models Solid Source anglesiteSolidSource.cif -Bulk anglesite crystal with incorporated PuO2+ used for reaction equations with solid sources and sinks. anhdyriteSolidSource.cif -Bulk anhydrite crystal with incorporated PuO2+ used for reaction equations with solid sources and sinks. aragoniteSolidSource.cif -Bulk aragonite crystal with incorporated PuO2+ used for reaction equations with solid sources and sinks. bariteSolidSource.cif -Bulk barite crystal with incorporated PuO2+ used for reaction equations with solid sources and sinks. calciteSolidSource.cif -Bulk calcite crystal with incorporated PuO2+ used for reaction equations with solid sources and sinks. celestineSolidSource.cif -Bulk celestine crystal with incorporated PuO2+ used for reaction equations with solid sources and sinks. Pu2O5SolidSource.cif -Bulk pentavalent Pu oxide: Pu2O5 crystal. Aqueous Source anglesiteAqSource.cif -Bulk anglesite crystal with incorporated PuO2+ used for reaction equations with aqueous sources and sinks. anhydriteAqSource.cif -Bulk anhydrite crystal with incorporated PuO2+ used for reaction equations with aqueous sources and sinks. aragoniteAqSource.cif -Bulk aragonite crystal with incorporated PuO2+ used for reaction equations with aqueous sources and sinks. bariteAqSource.cif -Bulk barite crystal with incorporated PuO2+ used for reaction equations with aqueous sources and sinks. calciteAqSource.cif -Bulk calcite crystal with incorporated PuO2+ used for reaction equations with aqueous sources and sinks. celestineAqSource.cif -Bulk celestine crystal with incorporated PuO2+ used for reaction equations with aqueous sources and sinks. Stepwise Incorporation anglesiteFig4.cif -Bulk anglesite crystal used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4. anglesiteFig4A.cif -Anglesite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4A. anglesiteFig4B.cif -Anglesite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4B. anglesiteFig4C.cif -Anglesite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4C. anglesiteFig4D.cif -Anglesite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4D. anglesiteFig4E.cif -Anglesite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4E. anglesiteFig4F.cif -Anglesite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4F. anhydriteFig4.cif -Bulk anhydrite crystal used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4. anhydriteFig4A.cif -Anhydrite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4A. anhydriteFig4B.cif -Anhydrite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4B. anhydriteFig4C.cif -Anhydrite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4C. anhydriteFig4D.cif -Anhydrite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4D. anhydriteFig4E.cif -Anhydrite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4E. anhydriteFig4F.cif -Anhydrite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4F. aragoniteFig4.cif -Bulk aragonite crystal used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4. aragoniteFig4A.cif -Aragonite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4A. aragoniteFig4B.cif -Aragonite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4B. aragoniteFig4C.cif -Aragonite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4C. aragoniteFig4D.cif -Aragonite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4D. aragoniteFig4E.cif -Aragonite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4E. aragoniteFig4F.cif -Aragonite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4F. bariteFig4.cif -Bulk barite crystal used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4. bariteFig4A.cif -Barite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4A. bariteFig4B.cif -Barite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4B. bariteFig4C.cif -Barite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4C. bariteFig4D.cif -Barite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4D. bariteFig4E.cif -Barite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4E. bariteFig4F.cif -Barite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4F. calciteFig4.cif -Bulk calcite crystal used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4. calciteFig4A.cif -Calcite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4A. calciteFig4B.cif -Calcite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4B. calciteFig4C.cif -Calcite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4C. calciteFig4D.cif -Calcite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4D. calciteFig4E.cif -Calcite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4E. calciteFig4F.cif -Calcite crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4F. celestineFig4.cif -Bulk celestine crystal used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4. celestineFig4A.cif -Celestine crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4A. celestineFig4B.cif -Celestine crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4B. celestineFig4C.cif -Celestine crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4C. celestineFig4D.cif -Celestine crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4D. celestineFig4E.cif -Celestine crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4E. celestineFig4F.cif -Celestine crystal surface used for reaction equations using the step-by-step incorporation method as referenced in the accompanying study in Figure 4F. Definition of Terms and Variables: No glossary is necessary for the uploaded molecular models. Use and Access: The file uploaded (.cif) are useable by any molecular modelling software. Any version of Materials Studio is recommended. Suggest a Citation for the Dataset: Gebarski, B. B. and Becker, U. Quantum-Mechanical Determination of the Incorporation of Pentavalent Plutonium into Carbonate and Sulfate Minerals. (2019) Geochimica et Cosmochimica Acta.