Diffusion and thermo-driven migration of silver, palladium, and ruthenium nanoparticles in cubic SiC matrix using molecular dynamics

The diffusion and thermo-driven migration behaviors of metal fission products in cubic SiC are critical for determining the safety of a high-temperature gas-cooled reactor, and the molecular dynamics (MD) approach can describe the phenomenon from a microscopic perspective. The interactions of three metal elements, Ag, Pd, Ru, and SiC, were described using the Analytical Bond-Order Potential (ABOP). The diffusion coefficient of metal nanoparticles within the SiC matrix was calculated at various temperatures, and the results revealed that Ag > Pd > Ru. Furthermore, thermo-driven migration simulations were carried out using three alternative matrix morphologies: pure cubic SiC, nano-polycrystalline SiC, and SiC with a nanochannel. It is illustrated that Ag nanoparticles transport farthest in the SiC nanocrack from the high-temperature region to the low-temperature region and the magnitude is considerably greater than that in the other two cases. Therefore, the size of the SiC nanochannel and metal nanoparticles were investigated additionally, indicating that there are optimal-matching geometric parameters for Ag and Ru, but no noticeable effect on Pd nanoparticles. The findings of this study allow for the calculation of the diffusion coefficient used in source term analysis, as well as the examination of fission product migration behavior in a large temperature gradient field.