Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
J Chem Phys. 2011 Sep 28;135(12):124711. doi: 10.1063/1.3640417.
We experimentally investigate the dynamics of particles constituting grain boundaries in a two-dimensional colloidal crystal, using video-microscopy. A clear plateau in the mean square displacement of the grain boundary particles is found, followed by an upswing indicative of cage breaking. The van Hove correlation functions and the non-Gaussian parameter show that grain boundary particle dynamics are highly heterogeneous. Furthermore, we identified clusters of cooperatively moving particles and analyzed the time-dependence of the weight-averaged mean cluster size. We find good correlation between the behavior of the mean square displacement, and the time dependence of the non-Gaussian parameter and the cluster size, as also reported for various supercooled systems. Our results therefore provide experimental support for the similarity between particle dynamics in grain boundaries and in supercooled liquids as suggested by recent computer simulations.
我们使用视频显微镜实验研究了二维胶体晶体中构成晶界的粒子的动力学。发现晶界粒子的均方位移出现明显的平台，随后出现表明笼破坏的上升。范霍夫相关函数和非高斯参数表明晶界粒子的动力学具有高度的不均匀性。此外，我们还识别了协同运动粒子的簇，并分析了加权平均簇大小的时间依赖性。我们发现均方位移的行为与非高斯参数和簇大小的时间依赖性之间存在良好的相关性，这与各种过冷系统的报告结果一致。因此，我们的结果为最近的计算机模拟所提出的晶界和过冷液体中粒子动力学之间的相似性提供了实验支持。
