First-Principles Study On The Plutonium Ions Interaction With Diamide Molecules In Acid Solutions

Theoretical study of the formation of PuZ+ (Z = 3, 4, 5, 6) complexes with the two types of diamide molecules C8N2H10O2(CH3)(2) (dimethylbicyclicdiamide-DMDA) with bicyclic structure and C3N2H2O2(CH3)(4) (tetramethylmalonamide-TMMA) with acyclic structure was carried out using ab initio DFT based DMol(3) and relativistic discrete variational methods. The results of gas phase modeling showed that the appropriate positions of the oxygen atoms in DMDA in comparison with TMMA cannot explain the considerable difference in sorption affinity of these molecules. For the modeling of solutions, the implicit (COSMO) and explicit methods were used. In the latter approach, we included 40 water molecules, 16NO(3)(-) or 16Cl(-) and 16H(+) ions into the systems under investigation. The obtained results showed the principle role of solution in the weakening of actinide bonding with TMMA and DMDA molecules due to interaction with H2O and NO3- or Cl- ions.