A DFT investigation of the interactions of Pd, Ag, Sn, and Cs with silicon carbide

Abstract

With a view to understand the diffusion of radionuclides through the silicon carbide layers in tristructural isotropic coated fuel particles, density functional theory calculations are applied to assess the interaction of palladium, silver, tin, and caesium with silicon carbide. The silicon carbide molecule (Si2C2), crystalline cubic silicon carbide (β‐SiC), and the (120) ∑5 grain boundary of β‐SiC are investigated to elucidate the differences in the interactions of silicon carbide with these elements. The main stabilizing forces in the PdSi2C2 complex were found to be donor‐acceptor charge transfer (covalent) interactions, the Ag and Sn complexes involve significant contributions from both electrostatic and covalent interactions, while the Cs atom is bonded dominantly by electrostatic forces. For the unconstrained MSi2C2 model, the following energetic ordering was obtained: Pd > Sn > Cs > Ag. The steric constraints in the bulk SiC and on the grain boundary change the order of binding energies to Pd > Ag > Sn > Cs in the interstitials and Pd > Sn > Ag > Cs in vacancies and at the grain boundary. By comparing the incorporation energies in the solid phases, it is possible to group these elements by similarities in the patterns of incorporation energies. Silver and palladium form a group with carbon, tin is grouped with silicon, and caesium is on its own. © 2014 European Commission. International Journal of Quantum Chemistry published by Wiley Periodicals, Inc.