Crystal nucleation and metastable bcc phase in charged colloids: A molecular dynamics study.
Crystal nucleation and metastable bcc phase in charged colloids: A molecular dynamics study.
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DOI：
10.1063/1.5016235
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发表时间：
2018-05
期刊：
影响因子：
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通讯作者：
X. Ji;Zhiwei Sun;Wenze Ouyang;Shenghua Xu
中科院分区：
文献类型：
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作者：
X. Ji;Zhiwei Sun;Wenze Ouyang;Shenghua Xu
用分子动力学方法研究了带电胶体均匀成核的动力学过程。为了验证液-固相变是否会通过亚稳体心立方结构，在确定位于亚稳体心立方结构相区内的状态点进行了模拟。模拟结果证实，在所有这些情况下，预先排序的前体，作为成核的种子，总是具有主导的bcc对称性与Ostwald的步骤规则和亚历山大-McTague机制一致。然而，多晶型物的选择并不简单，因为形成的晶体结构通常不取决于中间体前体的对称性，而是在不同的状态点下具有不同的特征。在晶化过程中形成足够大尺寸bcc晶体结构的状态点区域很窄，这合理地解释了为什么在宏观实验中很少检测到荷电胶体悬浮液中的亚稳bcc相。
The dynamic process of homogenous nucleation in charged colloids is investigated by brute-force molecular dynamics simulation. To check if the liquid-solid transition will pass through metastable bcc, simulations are performed at the state points that definitely lie in the phase region of thermodynamically stable fcc. The simulation results confirm that, in all of these cases, the preordered precursors, acting as the seeds of nucleation, always have predominant bcc symmetry consistent with Ostwald's step rule and the Alexander-McTague mechanism. However, the polymorph selection is not straightforward because the crystal structures formed are not often determined by the symmetry of intermediate precursors but have different characters under different state points. The region of the state point where bcc crystal structures of large enough size are formed during crystallization is narrow, which gives a reasonable explanation as to why the metastable bcc phase in charged colloidal suspensions is rarely detected in macroscopic experiments.