Revisiting the structures and energies of β-SiC [001] symmetric tilt grain boundaries

Structures and energetics of grain boundaries (GBs) can significantly modulate various properties of polycrystals. Previous studies focus on the ground-state GB structures of beta-SiC while the metastable states are poorly understood. Herein, atomistic simulations are employed to generate metastable structures for a series of [001] symmetric tilt GBs in beta-SiC. Structural units (SUs) based on the edge dislocation core structures are defined to characterize the GB structures. All GB structures can be divided into four types according to their different constituent SUs. Various distributions, orderings and combinations of SUs can generate multiple metastable structures with different GB energies. Furthermore, our calculations of low-angle GB energies agree well with the theoretical predictions based on the continuum elasticity theory. Our findings not only enhance the fundamental understanding of the (meta)stable grain boundary energetics and structural characteristics but also have significant implications for micro-structure design and grain boundary engineering in polycrystalline SiC.