Thermodynamics of solid solutions based on first-principles simulations of supercells of host phases with defects of the solute component
Zusammenfassung der Projektergebnisse
1) The research along the proposed program has allowed us to solve two problems, which are very important in the context of safety of long-term nuclear waste storage. We have shown that barite is a very efficient scavenger of 226Ra, while calcite is not a very good candidate for the long-term retention of 79Se. On the other hand, the relative easiness of Se incorporation into the calcite surface may be used for designing methods of purification of waters contaminated by Se. 2) Our research has shown that the thermodynamic parameters assessed with the aid of atomistic simulations appear to be in a good agreement with available experimental data. Consequently, the paradigm, maintaining that reliable thermodynamic properties of mixing of a solid solution could be obtained only from an experiment, has to be modified. This conclusion is particularly important for geoecology and radiogeochemistry, because for many relevant systems, i.e. for those containing active radionuclides, an experimental investigation is often prohibited. 3) We have shown that co-precipitation experiments performed under supersaturated conditions should not be directly interpreted within the concept of bulk equilibrium thermodynamics, while surface effects could predominate. On the other hand, we have shown that the surface adsorption and surface entrapment phenomena can be quantitatively described within the usual thermodynamic formalism, when the bulk endmembers are conceptually substituted with surface endmembers. 4) The project outlines the importance of distinguishing and comparing the effects of bulk and surface uptake due to solid solution formation. Mixing properties in the surface layer and in the bulk could be very different. This conclusion opens a new research area, where DFT calculations along the scheme proposed by Heberling et al. (2014) would provide exciting insights.
Projektbezogene Publikationen (Auswahl)
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(2013) Phase equilibria of (Mg,Fe)2SiO4 at the Earth at upper mantle conditions from first-principles studies. Physics of the Earth and Planetary Interiors, 217: 36 – 47
Y.G. Yu, V.L. Vinograd, B. Winkler, and R.M. Wentzcovitch
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(2013) Solid-aqueous equilibrium in the BaSO4-RaSO4-H2O system: first-principles calculations and a thermodynamic assessment. Geochim. Cosmochim. Acta, 122: 398−417
Vinograd V.L., Brandt F., Rozov K., Klinkenberg M., Refson K., Winkler B., Bosbach D.
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(2013) Statistical Thermodynamics of Geomaterials. Habilitationschrift. Goethe University, Frankfurt a. M.
Vinograd V.L.
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(2014) A thermodynamic adsorption/entrapment model for selenium(IV) coprecipitation with calcite. Geochim. Cosmochim. Acta, 134: 16–38
Heberling F., Vinograd V.L., Heck S., Rothe J., Schäfer Th,, Winkler B., Bosbach D., Geckeis H.
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(2014) Ab initio calculation of excess properties of La1-x(Ln,An)xPO4 solid solutions. Solid State Chemistry, 220: 137
Li ,Y., Kowalski, P., Blanca-Romero, A., Vinograd V.L., Bosbach D.
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(2014) Reactivity of the calcite-water-interface, from molecular scale processes to geochemical engineering. Applied Geochemistry, 45: 158-190
Heberling F., Bosbach D., Eckhardt J-D., Fischer U., Glowacky J., Haist M., Kramar U., Loos S., Müller H.S., Neumann Th, Pust C., Schäfer Th., Stelling J., Ukrainczyk M., Vinograd V.L., Vučak M., Winkler B.
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“Heat capacities of lanthanide and actinide monazite-type ceramics”, Journal of Nuclear Materials, 464, 147–154 (2015)
Kowalski, P. M., Beridze, G., Vinograd, V. & Bosbach, D.
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(2016) Thermodynamics of mixing in an isostructural solid solution: Simulation methodologies and application to the rutile-cassiterite system. American Mineralogist, 101: 1197-1206
Liu, X., Vinograd, V.L., Lu, X.,, Leonenko, E.V. , Eremin, N.N., Wang, R., Winkler, B.
