Lechner Wolfgang, Polster David, Maret Georg, Dellago Christoph, Keim Peter
Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, 6020 Innsbruck, Austria.
Institute for Theoretical Physics, University of Innsbruck, 6020 Innsbruck, Austria.
Phys Rev E Stat Nonlin Soft Matter Phys. 2015 Mar;91(3):032304. doi: 10.1103/PhysRevE.91.032304. Epub 2015 Mar 5.
We study in experiment and with computer simulation the free energy and the kinetics of vacancy and interstitial defects in two-dimensional dipolar crystals. The defects appear in different local topologies, which we characterize by their point group symmetry; Cn is the n-fold cyclic group and Dn is the dihedral group, including reflections. The frequency of different local topologies is not determined by their almost degenerate energies but is dominated by entropy for symmetric configurations. The kinetics of the defects is fully reproduced by a master equation in a multistate Markov model. In this model, the system is described by the state of the defect and the time evolution is given by transitions occurring with particular rates. These transition rate constants are extracted from experiments and simulations using an optimization procedure. The good agreement between experiment, simulation, and master equation thus provides evidence for the accuracy of the model.
我们通过实验和计算机模拟研究二维偶极晶体中空位和间隙缺陷的自由能及动力学。缺陷以不同的局部拓扑结构出现，我们通过其点群对称性对其进行表征；Cn 是 n 重循环群，Dn 是二面体群，包括反射。不同局部拓扑结构的频率并非由其几乎简并的能量决定，而是由对称构型的熵主导。缺陷的动力学由多态马尔可夫模型中的主方程完全重现。在该模型中，系统由缺陷状态描述，时间演化由以特定速率发生的跃迁给出。这些跃迁速率常数通过优化程序从实验和模拟中提取。实验、模拟和主方程之间的良好一致性因此为模型的准确性提供了证据。
