HCP-Mg平衡固液界面的微观结构

采用NVE系综分子动力学(molecular dynamics,MD)方法模拟了HCP-Mg三个不同晶向的平衡固液界面,通过原子标定技术,在"layering and in-plane ordering"框架内,对固液界面的结构特征进行了分析。在验证了势函数有效性的基础上,通过界面微观结构分析发现,序参数在由固相向液相衰减的过程中呈现了很好的双曲正切的连续变化规律;以序参数aq6为标准计算得到的界面宽度要比序参数ξ的界面宽度大0.1~0.2 nm;同时,界面宽度存在各向异性,[0001]方向界面宽度最大,[11ˉ00]和[1ˉ21ˉ0]方向界面宽度基本相等,这与界面热力学的各向异性保持一致;界面的波动幅度达到界面宽度的5%~10%;此外,Layering方法定位的界面宽度要远远超过in-plane ordering方法定位的界面宽度,吻合于异质固液界面的试验观察。

Microstructure of equilibrium solid-liquid interface of HCP-Mg

The NVE ensemble molecular dynamics (MD) simulation was applied to analyze the microstructure of the equilibrium solid-liquid interface of HCP-Mg in three low-index orientations. The analysis is within the framework of"layering and in-plane ordering"and the key is the technique of atom identification. Based on the fully validation of se-lected atom interaction potential,a great deal of equilibrium solid-liquid interface configurations was obtained for subse-quent analysis and the following conclusions from it were reached. All order parameters show hyperbolic tangent profiles decaying from bulk solid to liquid. The interfacial width from aq6 is 0.1-0.2 nm larger than those of the correspondingξ. The interfacial width in [0001] orientation is larger than those in other [ 1ˉ21ˉ0 ] and [ 11ˉ00 ] orientations,which repre-sents the anisotropy of structure coinciding with the anisotropy of interfacial thermodynamics. The fluctuation amplitude is as large as 5%-10%of the corresponding interface width. In addition,the width in frame of layering is truly larger than that in frame of in-plane ordering,which was observed in the HRTEM of heterogeneous interface.