Rietz Frank, Radin Charles, Swinney Harry L, Schröter Matthias
Max-Planck-Institute for Dynamics and Self-Organization Göttingen, 37077 Göttingen, Germany.
Institute for Multiscale Simulation, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91052 Erlangen, Germany.
Phys Rev Lett. 2018 Feb 2;120(5):055701. doi: 10.1103/PhysRevLett.120.055701.
We present an experiment on crystallization of packings of macroscopic granular spheres. This system is often considered to be a model for thermally driven atomic or colloidal systems. Cyclically shearing a packing of frictional spheres, we observe a first order phase transition from a disordered to an ordered state. The ordered state consists of crystallites of mixed fcc and hcp symmetry that coexist with the amorphous bulk. The transition, initiated by homogeneous nucleation, overcomes a barrier at 64.5% volume fraction. Nucleation consists predominantly of the dissolving of small nuclei and the growth of nuclei that have reached a critical size of about ten spheres.
我们展示了一个关于宏观颗粒球体堆积结晶的实验。该系统常被视为热驱动原子或胶体系统的模型。通过循环剪切摩擦球体的堆积，我们观察到从无序状态到有序状态的一级相变。有序状态由具有混合面心立方（fcc）和六方密堆积（hcp）对称性的微晶组成，它们与无定形主体共存。由均匀成核引发的转变在体积分数为64.5%时克服了一个势垒。成核主要包括小核的溶解和已达到约十个球体临界尺寸的核的生长。
