Authors
Ljiljana Stojanović, Samuel J Magorrian, Lara Kabalan, Richard N White, Fabian L Thiemann, Viktor Zólyomi
Published in
The Journal of chemical physics. Volume 165. Issue 15. Oct 21, 2026.
Abstract
Predicting how crystal structure influences high-temperature stability remains a key challenge in materials modeling and design. Silicon carbide (SiC), one of the most thermally and chemically stable materials known, provides an ideal system for studying this problem because its many polytypes preserve similar local tetrahedral bonding while differing in long-range stacking geometry. To determine the impact of polytype structure on the high-temperature stability of SiC, we combine phase-coexistence machine-learning molecular dynamics with finite-temperature phonon analysis, enabled by a fine-tuned MACE interatomic potential that accurately describes crystalline, high-temperature, and disordered configurations across multiple SiC polytypes. We identify a clear stability ordering, 3C > 2H > 9R, reflected consistently in structural disordering, interlayer sliding, and finite-temperature phonon spectra. Across all polytypes, melting initiates through the formation of short C-C contacts and carbon-rich local regions, followed by a progressive loss of tetrahedral Si-C connectivity. The reduced stability of the long-period 9R polytype is associated with a denser manifold of low-frequency transverse-acoustic modes arising from its stacking periodicity and associated zone folding, which broaden and soften further at high temperature. These modes can provide additional low-energy channels for thermally activated lateral bilayer motion, consistent with the larger sliding amplitudes observed in 9R and their positive correlation with local structural disorder.
PMID:
42895431
Bibliographic data and abstract were imported from PubMed on 19 Oct 2026.
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