Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
J Chem Phys. 2011 Jan 21;134(3):034506. doi: 10.1063/1.3545967.
We studied the two-dimensional freezing transitions in monolayers of microgel colloidal spheres with short-ranged repulsions in video-microscopy experiments, and monolayers of hard disks, and Yukawa particles in simulations. These systems share two common features at the freezing points: (1) the bimodal distribution profile of the local orientational order parameter; (2) the two-body excess entropy, s(2), reaches -4.5±0.5 k(B). Both features are robust and sensitive to the freezing points, so that they can potentially serve as empirical freezing criteria in two dimensions. Compared with the conventional freezing criteria, the first feature has no finite-size ambiguities and can be resolved adequately with much less statistics; and the second feature can be directly measured in macroscopic experiments without the need for microscopic information.
我们通过视频显微镜实验研究了具有短程排斥力的微凝胶胶体球单层中的二维冷冻转变，以及模拟中的硬磁盘和 Yukawa 粒子单层。这些系统在冰点处有两个共同特征：（1）局部方位有序参数的双峰分布轮廓；（2）双体过剩熵 s(2)达到-4.5±0.5 k(B)。这两个特征都是稳健的，对冰点敏感，因此它们有可能在二维空间中作为经验冻结标准。与传统的冻结标准相比，第一个特征没有有限尺寸的模糊性，可以用更少的统计数据充分解决；第二个特征可以在宏观实验中直接测量，而无需微观信息。
