Atomistic Investigation of Thermophysical Properties of Actinide Chlorides-Based Molten Salts via <i>Ab Initio</i> Molecular Dynamics and the Polarizable Ion Model

Chloride-based molten salts are increasingly attracting interest as potential nuclear fuels for minor actinide transmutation. However, knowledge of their thermophysical properties remains limited. As experimental studies of molten salts are very challenging, atomistic simulations have become an essential tool for predicting these properties. Here, we present an atomic-scale study of pure UCl₃, PuCl₃, and AmCl₃, and of their eutectic mixtures with NaCl by combining Density Functional Theory (DFT) and Classical Molecular Dynamics (CMD) with Polarizable Ion Model (PIM) potential. <i>Ab initio</i> 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 the 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 the reactor design.