First principles modeling of plutonium complexation in nitric and hydrochloric acid solutions

Abstract The formation of plutonium (III–VI) complexes in nitric and hydrochloric acid solutions was simulated using DMol 3 and Relativistic Discrete-Variational (RDV) methods. Both explicit and explicit-plus-implicit approaches for the modeling of solution boundary conditions were used. For the explicit modeling of molecular environment of plutonium ions we used 22 and 32 water molecules and the counter ions NO 3 − or Cl − randomly distributed around actinide atom. For the additional implicit modeling of solvent environment, COSMO potential (Conductor-like Screening Model) for water ( ε = 78.54) was used. The original method for the calculation of interaction energies between selected parts of the large multi-atomic systems provides the quantitative comparison of the stability of plutonium complexes with various compositions and the estimation of the roles of NO 3 − , Cl − and water molecules of the nearest and next-nearest solution layers. We obtained that the average interaction energies between Pu Z+ ion and each nearest H 2 O molecule were slightly dependent on the size and composition of optimized plutonium complex.