Wang Ziren, Wang Feng, Peng Yi, Han Yilong
Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong SAR, China.
Nat Commun. 2015 Apr 21;6:6942. doi: 10.1038/ncomms7942.
The growth behaviour of liquid nucleus is crucial for crystal melting, but its kinetics is difficult to predict and remains challenging in experiment. Here we directly observed the growth of individual liquid nuclei in homogeneous melting of three-dimensional superheated colloidal crystals with single-particle dynamics by video microscopy. The growth rate of nucleus at weak superheating is well fitted by generalizing the Wilson-Frenkel law of crystallization to melting and including the surface tension effects and non-spherical-shape effects. As the degree of superheating increases, the growth rate is enhanced by nucleus shape fluctuation, nuclei coalescence and multimer attachment. The results provide new guidance for the refinement of nucleation theory, especially for the poorly understood strong-superheating regime. The universal Lindemann parameter observed at the superheat limit and solid-liquid interfaces indicates a connection between homogeneous and heterogeneous melting.
液核的生长行为对晶体熔化至关重要，但其动力学难以预测，在实验中仍然具有挑战性。在此，我们通过视频显微镜，利用单粒子动力学直接观察了三维过热胶体晶体均匀熔化过程中单个液核的生长情况。通过将结晶的威尔逊-弗伦克尔定律推广到熔化过程，并考虑表面张力效应和非球形效应，弱过热条件下核的生长速率得到了很好的拟合。随着过热度的增加，核形状波动、核聚并和多聚体附着会提高生长速率。这些结果为成核理论的完善提供了新的指导，特别是对于理解不足的强过热区域。在过热极限和固液界面观察到的通用林德曼参数表明了均匀熔化和非均匀熔化之间的联系。
