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<p>The nucleation and growth of graphite in Fe-C alloys (cast iron) can both be related to the 2-D nucleation of a single atomic layer of graphene. Here, we use molecular dynamics (MD) simulations to study the nucleation of graphite from molten iron. A neural-network potential is developed for the Fe-C system using a pragmatic approach to treat the paramagnetic nature of liquid iron, and its thermodynamic behavior is validated against data from thermochemical software. The critical nucleus size and free-energy barrier for nucleation are computed using MD simulations in combination with enhanced sampling methods, and the results are compared with continuum models based on adaptations of classical nucleation theory. 2-D nucleation is found to be a feasible mechanism for graphite nucleation and growth at a carbon supersaturation of 5 at.% or higher. At low supersaturation the nucleation rate declines, and other mechanisms such as interaction with substrates other than graphite, solute elements, or defects are necessary to facilitate the formation of new layers.</p>

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Molecular dynamics study of graphite 2-D nucleation from paramagnetic Fe-C melt

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月9日

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  • Adam Götz,
  • Daniel Marchand,
  • Leander Michels,
  • Jaakko Akola

摘要

The nucleation and growth of graphite in Fe-C alloys (cast iron) can both be related to the 2-D nucleation of a single atomic layer of graphene. Here, we use molecular dynamics (MD) simulations to study the nucleation of graphite from molten iron. A neural-network potential is developed for the Fe-C system using a pragmatic approach to treat the paramagnetic nature of liquid iron, and its thermodynamic behavior is validated against data from thermochemical software. The critical nucleus size and free-energy barrier for nucleation are computed using MD simulations in combination with enhanced sampling methods, and the results are compared with continuum models based on adaptations of classical nucleation theory. 2-D nucleation is found to be a feasible mechanism for graphite nucleation and growth at a carbon supersaturation of 5 at.% or higher. At low supersaturation the nucleation rate declines, and other mechanisms such as interaction with substrates other than graphite, solute elements, or defects are necessary to facilitate the formation of new layers.