Silicon oxycarbides show outstanding versatility due to their highly tunable composition and microstructure. Consequently, a key challenge is a thorough knowledge of structure–property relations in the system. In this work, we fit an atomic cluster expansion potential to a set of actively learned density-functional theory training data spanning a wide configurational space. We demonstrate the ability of the potential to produce realistic amorphous structures and rationalize the formation of different morphologies of the turbostratic free carbon phase. Finally, we relate the materials stiffness to its composition and microstructure, finding a delicate dependence on Si-C bonds that contradicts commonly assumed relations to the free carbon phase.

N. L. acknowledges Linus C. Erhard for helpful discussions. N. L. received funding from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under grant number 405621137 and from the German Federal Ministry of Education and Research (BMBF) under project HeNa (FKZ 03XP0390A). J. R. acknowledges funding from the European Unions Horizon 2020 research and innovation program under Grant Agreement no. 963542. K. A. acknowledges funding by the DFG under project number 413956820