Comparative study of crystallization process in metallic melts using ab initio molecular dynamics simulations
Comparative study of crystallization process in metallic melts using ab initio molecular dynamics simulations
复制标题
使用从头算分子动力学模拟对金属熔体结晶过程进行比较研究
DOI：
10.1088/1361-648x/aa66a8
复制
发表时间：
2017-05-10
影响因子：
2.7
通讯作者：
Jiang, J. Z.
中科院分区：
文献类型：
--
作者：
Debela, Tekalign T.;Wang, X. D.;Jiang, J. Z.
采用从头算分子动力学方法研究了液态金属的结晶过程。在铅和锌液体淬火过程中的短程有序的演变进行了比较，体心立方（bcc）的Nb和V，和六方密排（hcp）的Mg。我们发现短程有序的分数和类型取决于所考虑的系统，其中二十面体对称性似乎在体心立方金属中占主导地位。虽然在稳定的液体中的局部原子结构是相似的，液体hcp类Zn，bcc类Nb和V可以在结晶前远低于其熔点的深度过冷，而在液体Pb的过冷温度范围是有限的。对成核过程的进一步研究揭示了多晶型选择的过程。在体心立方体系中，多晶型选择发生在成核开始之前的过冷状态，而在密堆积体系中，多晶型选择开始于结晶开始时。在所研究的过冷液体中，具有类bcc晶格的原子总是在多晶型选择之前被检测到。研究还发现，在过冷Zn和Pb液体中，键的取向有序与结晶过程密切相关。
The crystallization process of liquid metals is studied using ab initio molecular dynamics simulations. The evolution of short-range order during quenching in Pb and Zn liquids is compared with body-centered cubic (bcc) Nb and V, and hexagonal closed-packed (hcp) Mg. We found that the fraction and type of the short-range order depends on the system under consideration, in which the icosahedral symmetry seems to dominate in the body-centered cubic metals. Although the local atomic structures in stable liquids are similar, liquid hcp-like Zn, bcc-like Nb and V can be deeply supercooled far below its melting point before crystallization while the supercooled temperature range in liquid Pb is limited. Further investigations into the nucleation process reveal the process of polymorph selection. In the body-centered cubic systems, the polymorph selection occurs in the supercooled state before the nucleation is initiated, while in the closed-packed systems it starts at the time of onset of crystallization. Atoms with bcc-like lattices in all studied supercooled liquids are always detected before the polymorph selection. It is also found that the bond orientational ordering is strongly correlated with the crystallization process in supercooled Zn and Pb liquids.