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首页> 外文期刊>The Journal of Chemical Physics >Phase field theory of interfaces and crystal nucleation in a eutectic system of fcc structure:I.Transitions in the one-phase liquid region
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Phase field theory of interfaces and crystal nucleation in a eutectic system of fcc structure:I.Transitions in the one-phase liquid region

机译：fcc结构共晶体系中界面和晶体成核的相场理论：I。一相液相区的跃迁

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摘要

The phase field theory(PFT)has been applied to predict equilibrium interfacial properties and nucleation barrier in the binary eutectic system Ag-Cu using double well and interpolation functions deduced from a Ginzburg-Landau expansion that considers fcc(face centered cubic)crystal symmetries.The temperature and composition dependent free energies of the liquid and solid phases are taken from CALculation of PHAse Diagrams-type calculations.The model parameters of PFT are fixed so as to recover an interface thickness of ~1 nm from molecular dynamics simulations and the interfacial free energies from the experimental dihedral angles available for the pure components.A nontrivial temperature and composition dependence for the equilibrium interfacial free energy is observed.Mapping the possible nucleation pathways,we find that the Ag and Cu rich critical fluctuations compete against each other in the neighborhood of the eutectic composition.The Tolman length is positive and shows a maximum as a function of undercooling.The PFT predictions for the critical undercooling are found to be consistent with experimental results.These results support the view that heterogeneous nucleation took place in the undercooling experiments available at present.We also present calculations using the classical droplet model[classical nucleation theory(CNT)]and a phenomenological diffuse interface theory(DIT).While the predictions of the CNT with a purely entropic interfacial free energy underestimate the critical undercooling,the DIT results appear to be in a reasonable agreement with the PFT predictions.
机译：应用相场理论（PFT）来预测双相共晶系统Ag-Cu的平衡界面性质和成核势垒，使用的双井和插值函数由考虑到fcc（面心立方）晶体对称性的Ginzburg-Landau展开导出。液相和固相随温度和组成的自由能取自PHAse图类型计算的计算值。固定了PFT的模型参数，以便从分子动力学模拟和界面自由中获得约1 nm的界面厚度从纯组分的实验二面角获得能量。观察到平衡界面自由能的非平凡温度和成分依赖性。映射可能的成核途径，我们发现富含Ag和Cu的临界波动在附近相互竞争。共晶成分的托尔曼长度为正并显示出最大值临界过冷的PFT预测与实验结果一致。这些结果支持这样的观点：目前可用的过冷实验中发生了非均相形核。我们还提出了使用经典液滴模型的计算[经典的成核理论（CNT）和现象学的扩散界面理论（DIT）。尽管纯熵界面自由能对CNT的预测低估了临界过冷，但DIT的结果似乎与PFT的预测合理地吻合。

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