Zhang Huijun, Peng Shuming, Mao Li, Zhou Xiaosong, Liang Jianhua, Wan Chubin, Zheng Jian, Ju Xin
School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China and Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China.
Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China.
Phys Rev E Stat Nonlin Soft Matter Phys. 2014 Jun;89(6):062410. doi: 10.1103/PhysRevE.89.062410. Epub 2014 Jun 30.
Using molecular dynamics simulations, we study freezing of Lennard-Jones particles at commensurate substrate with triangular pattern. Throughout the box particles freeze onto the substrate and form close-packed layers. For the moderately attractive substrates, an intermediate hexatic phase between liquid and crystal is detected in the first two layers where the hexatic-solid freezing process is continuous while, counterintuitively, the liquid-hexatic process is of first order. Moreover, we observe that liquid-hexatic and hexatic-solid transitions shift towards higher temperatures with the attraction strength increasing. By contrast, the liquid-hexatic transition shifts faster than the hexatic-solid process, significantly widening the temperature range of the hexatic phase. When this phenomenon appears, freezing in the bulk always proceeds through a first-order transition at the same temperature. In addition, changes in the average structural order (three-dimensional) of the layers indicate that freezing processes in layers near substrates seem to cost the structural order of the bulk particles in their vicinity, and an intermediate prestructural cloud of medium-ordered particles is always observed before the layering freezing.
利用分子动力学模拟，我们研究了具有三角形图案的相称衬底上 Lennard-Jones 粒子的冻结过程。在整个盒子中，粒子冻结在衬底上并形成密堆积层。对于中等吸引力的衬底，在前两层中检测到液体和晶体之间的中间六方相，其中六方-固体冻结过程是连续的，而与直觉相反的是，液体-六方过程是一级的。此外，我们观察到液体-六方和六方-固体转变随着吸引力强度的增加而向更高温度移动。相比之下，液体-六方转变比六方-固体过程移动得更快，显著拓宽了六方相的温度范围。当这种现象出现时，整体中的冻结总是在相同温度下通过一级转变进行。此外，层的平均结构有序度（三维）的变化表明，衬底附近层中的冻结过程似乎消耗了其附近整体粒子的结构有序度，并且在分层冻结之前总是观察到中等有序粒子的中间预结构云。
