Identification of critical nuclei in the rapid solidification via configuration heredity

The identification and characterization of critical nuclei is a long-standing issue in the rapid solidification of metals and alloys. An ambiguous description for their sizes and shapes used to lead to an overestimation or underestimation of homogeneous nucleation rates I (T) in the framework of classical nucleation theory ( CNT). In this paper, a unique method able to distinguish the critical nucleus from numerous embryos is put forward on the basis of configuration heredities of clusters during rapid solidifications. As this technique is applied to analyze the formation and evolution of various fcc-Al single crystal clusters in a large-scale molecular dynamics simulation system, it is found that the size n(c) and geometrical configuration of critical nuclei as well as their liquid- solid interfacial structure can be determined directly. For the present deep super- cooled system with an undercooling of T-m = 0.42T(m)(cal) , the average size of critical nuclei is demonstrated to be n(c) approximate to 26, but most of which are non-spherical lamellae. Also, their liquid-solid interfaces are revealed to be not an fcc-liquid duplex-phase interface but an fcc/hcp-liquid multi-phase structure. These findings shed some lights on the CNT, and a good agreement with previous simulations and experiments in I (T) indicates this technique can be used to explore the early-stage of nucleation from atomistic levels.

Automated summary

This study introduces a novel method to directly determine the size, shape, and liquid-solid interface structure of critical nuclei during rapid solidification processes. The average size of critical nuclei is found to be approximately 26 atoms in a deep super-cooled system, most of which are non-spherical lamellae. These findings provide valuable insights into classical nucleation theory and are in good agreement with previous simulations and experiments.