Atomistic mechanisms of phase separation and formation of solid solutions: model studies of NaCl, NaCl-NaF, and Na(Cl1-xBrx) crystallization from the melt.
Atomistic mechanisms of phase separation and formation of solid solutions: model studies of NaCl, NaCl-NaF, and Na(Cl1-xBrx) crystallization from the melt.
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相分离和固溶体形成的原子机制：熔体中 NaCl、NaCl-NaF 和 Na(Cl1-xBrx) 结晶的模型研究。
DOI：
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发表时间：
2007
影响因子：
3.3
通讯作者：
D. Zahn
中科院分区：
文献类型：
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作者：
D. Zahn
采用过渡路径取样分子动力学模拟方法研究了氯化钠从其熔体及与其它卤化钠混合物中的结晶过程。从这一点上，我们探讨了在原子层次上的细节的凝固和熔化过程的成核机制。通过掺入杂质，共晶混合物的成核图像发生了相当大的变化。在NaCl晶体中掺杂氟离子，我们观察到替代缺陷作为熔融转变的有利成核中心。这种现象在低NaF浓度的NaCl-NaF熔体的凝固过程中起着关键作用，并被证明是氟离子偏析的原因。虽然NaCl-NaF对应于低共熔体系，但我们也研究了NaCl-NaBr混合物。观察到溴离子的行为与氯离子非常相似。因此，没有发生相分离，并形成Na（Cl 1-xBrx）固溶体。在这两个原型的例子中，我们展示了研究的原子机制相关的相分离过程和固溶体的形成过程中的成核和生长的晶体从多元熔体。
The crystallization of sodium chloride from its melt and mixtures with other sodium halides is investigated by means of transition path sampling molecular dynamics simulations. From this we explore the nucleation mechanisms of both the solidification and the melting process at the atomistic level of detail. By incorporation of impurities the nucleation picture of the eutectic mixtures changes considerably. Doping the NaCl crystal with fluoride ions, we observed the substitutional defects to act as favored nucleation centers for the melting transition. This phenomenon plays a critical role during the solidification process of NaCl-NaF melts of low NaF concentration and is demonstrated to account for the segregation of fluoride ions. While NaCl-NaF corresponds to a eutectic system, we also investigated NaCl-NaBr mixtures. The bromide ions were observed to behave very similarly to chloride ions. As a consequence, no phase separation occurs and Na(Cl1-xBrx) solid solutions are formed. At the example of these two prototypes we demonstrate the study of the atomistic mechanisms related to phase separation processes and solid solution formation during the nucleation and growth of crystals from multinary melts.