Mechanical and irradiation behavior of SiC polytypes: Atomistic insights on plastic deformation, damage resistance, and unified performance metric

SK Sahni and H Abdolvand and A Kona, CERAMICS INTERNATIONAL, 51, 64768-64783 (2025).

DOI: 10.1016/j.ceramint.2025.11.210

Silicon carbide (SiC) is a critical material in advanced nuclear energy systems due to its excellent mechanical strength and radiation resistance under extreme reactor conditions. Understanding its deformation mechanisms and radiation tolerance at the atomic scale is essential for ensuring long-term reliability under extreme conditions. This study employs large-scale molecular dynamics (MD) simulations to investigate both irradiationinduced defect evolution and dislocation- mediated plasticity in three SiC polytypes (3C, 4H, and 6H) under mechanical and radiation environments. Under indentation, 3C-SiC accommodates plasticity primarily by 1/2<110> glide on 111 systems, forming dense dislocation networks and prismatic loops, whereas hexagonal 4H and 6H favor basal slip, extensive stacking faults. All polytypes show localized amorphization under the indenter, with 6H exhibiting the largest lateral amorphous zones. Irradiation cascades produce an interstitialcarbon dominated defect and nearly linear defect accumulation with sequential PKAs. 3C-SiC retains the most surviving defects and forms the largest defect clusters, while 4H/6H produce smaller, more localized clusters A unified analysis of mechanical and irradiation responses, based on dislocation density, shear modulus, surviving defect counts, clustering fraction, and amorphous volume fraction, reveals that 3C-SiC surpasses hexagonal polytypes by accommodating stress more effectively despite generating more defects. These parameters are synthesized into a novel Radiation Tolerance Index (RTI) to quantify this performance.

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