Atomistic investigation of thermophysical properties of actinide chlorides based molten salts via ab initio Molecular Dynamics and Polarizable Ion Model

Chloride based molten salts are increasingly attracting interest as potential nuclear fuels for minor actinide transmutation. However, knowledge of these materials remains limited, and experimental challenges limit a complete characterization of their thermophysical properties. Atomistic simulations are therefore essential. Here, we present an atomic scale study of pure and NaCl based binary mixtures of UCl3, PuCl3, and AmCl3 combining Density Functional Theory (DFT) and Classical Molecular Dynamics (CMD) with Polarized Ion Model (PIM) potentials. Ab initio Molecular Dynamics (AIMD) calculations show that including Grimme’s DFT-D3 correction improves agreement with experimental ionic bond lengths (BLs) and coordination numbers (CNs) in UCl3, guiding the development of new force fields for PuCl3 and AmCl3. CMD simulations with these potentials provide density, heat capacity, viscosity, and diffusivity. Americium containing systems exhibit higher density and viscosity, while DFT-D3 correction in plutonium yields a less defined coordination shell and lower viscosity. These results underscore the need to treat each actinide individually in reactor design.