Molecular dynamics study of high-temperature creep in carbon-rich amorphous silicon carbide: The role of local coordination

Abstract

The high-temperature creep resistance of polymer-derived carbon-rich amorphous silicon carbide (a-SiC) is critical for its application in extreme environments; however, the atomistic origins of its viscoplastic flow remain debated. In this study, molecular dynamics simulations combined with a coordination-resolved non-affine displacement ( D min 2 ) framework are used to investigate the structural mechanisms governing primary creep in a-SiC. By decoupling the effects of chemical identity and local network topology, we show that the apparent “hyper-mobility” of excess carbon is not an intrinsic chemical characteristic. Instead, viscoplastic flow is primarily topology-driven and governed by the preferential occupation of under-coordinated, high-free-volume sites by carbon atoms. These localized structural defects serve as nucleation sites for stress-activated atomic rearrangements, enabling the amorphous network to accommodate sustained viscoplastic strain while maintaining global connectivity. On the basis of these findings, we propose that future material optimization should shift from conventional macroscopic stoichiometric tuning toward “topological engineering.” Passivation of under-coordinated defects through thermomechanical densification, selective heteroatom cross-linking, or nanoscale interface pinning offers a targeted strategy for designing highly creep-resistant disordered covalent networks.

The authors' abstract, as published at the source. Journal of Non-Crystalline Solids, 2026 · DOI ↗