Ab initio modeling and thermodynamics of hydrated plutonium oxalates

Abstract

An ab initio study on the plutonium oxalate hydrates: Pu2(C2O4)3⋅10H2O and Pu(C2O4)2⋅6H2O, using PBE exchange-correlation with D3 dispersion correction and Hubbard correction for the plutonium atoms was performed and compared to experimental vibrational spectral and thermodynamic property values. We demonstrated that this technique can accurately predict the experimental infrared spectra Pu(III) oxalate hydrate, as well as the Raman peak of PuO2 (used to calculate the thermodynamic properties of the oxalates). For Pu(IV) oxalate hydrate, we found that our predicted structure agreed qualitatively with PXRD measurements, the only available experimental determination of the structure. Using this method at standard temperature and pressure, we predicted standard enthalpies of formation of -6,755 kJ mol−1 and -3,923 kJ mol−1 and standard Gibbs free energy of formation of -5,899 kJ mol−1 and -3,386 kJ mol−1 for Pu2(C2O4)3⋅10H2O and Pu(C2O4)2⋅6H2O, respectively.