Ab initio calculation of excess properties of La1−x(Ln,An)xPO4 solid solutions

Abstract We used ab initio computational approach to predict the excess enthalpy of mixing and the corresponding regular/subregular model parameters for La 1 − x Ln x PO 4 (Ln=Ce,…, Tb) and La 1 − x An x PO 4 (An=Pu, Am and Cm) monazite-type solid solutions. We found that the regular model interaction parameter W computed for La 1 − x Ln x PO 4 solid solutions matches the few existing experimental data. Within the lanthanide series W increases quadratically with the volume mismatch between LaPO4 and Ln PO 4 endmembers ( Δ V = V LaPO 4 − V Ln PO 4 ) , so that W ( kJ / mol ) = 0.618 ( Δ V ( cm 3 / mol ) ) 2 . We demonstrate that this relationship also fits the interaction parameters computed for La 1 − x An x PO 4 solid solutions. This shows that lanthanides can be used as surrogates for investigation of the thermodynamic mixing properties of actinide-bearing solid solutions.

[1]  D. Vanderbilt,et al.  Soft self-consistent pseudopotentials in a generalized eigenvalue formalism. , 1990, Physical review. B, Condensed matter.

[2]  R. D. Shannon.  Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides , 1976 .

[3]  M. Sluiter,et al.  Subsolidus phase relations in the CaCO3–MgCO3 system predicted from the excess enthalpies of supercell structures with single and double defects , 2009 .

[4]  Ariadna Blanca Romero,et al.  Performance of DFT+U method for prediction of structural and thermodynamic parameters of monazite‐type ceramics , 2014, J. Comput. Chem..

[5]  G. Scuseria,et al.  Restoring the density-gradient expansion for exchange in solids and surfaces. , 2007, Physical review letters.

[6]  Stefano de Gironcoli,et al.  QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials , 2009, Journal of physics. Condensed matter : an Institute of Physics journal.

[7]  David L. Olmsted,et al.  Efficient stochastic generation of special quasirandom structures , 2013 .

[8]  Hartmut Schlenz,et al.  Monazite as a suitable actinide waste form , 2013 .

[9]  Rudy J. M. Konings,et al.  High-temperature calorimetry of (La1−xLnx)PO4 solid solutions , 2007 .

[10]  M. Prieto.  Thermodynamics of Solid Solution-Aqueous Solution Systems , 2009 .

[11]  Marcus Walter,et al.  Excess properties of the (Ln2−2xCaxThx)(PO4)2 (Ln = La, Ce) solid solutions , 2008 .

[12]  F. Brandt,et al.  Solid–aqueous equilibrium in the BaSO4–RaSO4–H2O system: First-principles calculations and a thermodynamic assessment , 2013 .

[13]  Rodney C. Ewing,et al.  Phosphates as Nuclear Waste Forms , 2002 .

[14]  S. Stølen,et al.  Size mismatch effects in oxide solid solutions using Monte Carlo and configurational averaging. , 2005, Physical chemistry chemical physics : PCCP.

[15]  V. Heine,et al.  Scaling of thermodynamic mixing properties in garnet solid solutions , 2001 .

[16]  G. Plumlee.  Sulfate minerals- Crystallography, geochemistry and environmental significance , 2001 .

[17]  Ferreira,et al.  Special quasirandom structures. , 1990, Physical review letters.

[18]  M. Sluiter,et al.  Thermodynamics of mixing in pyrope-grossular, Mg3Al2Si3O12-Ca3Al2Si3O12, solid solution from lattice dynamics calculations and Monte Carlo simulations , 2006 .

[19]  Y. Kawazoe,et al.  Prediction of the mixing enthalpy of alloys , 2002 .