Huang Zihan, Zhu Guolong, Chen Pengyu, Hou Cuiling, Yan Li-Tang
State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
Phys Rev Lett. 2019 May 17;122(19):198002. doi: 10.1103/PhysRevLett.122.198002.
Colloidal Janus spheres in the bulk typically spontaneously assemble into plastic crystalline phases, while particle orientations exhibit glasslike dynamics without long-range order. Through Brownian dynamics simulations, we demonstrate that shear can trigger a phase transition from an isotropic crystal with orientational disorder to an orientationally ordered crystal with lamellae along the shear direction. This nonequilibrium transition is accompanied with the orientational ordering following a nucleation and growth mechanism. By performing a phenomenological extension of free energy analysis, we reveal that the nucleation originates from the orientation fluctuations induced by shear. The growth of the orientationally crystalline cluster is examined to be disklike, captured by developing a lattice model with memoryless state functions. These findings bring new insights into the mechanisms for the ordering transition of anisotropic particles at nonequilibrium states.
本体中的胶体双面球通常会自发组装成塑性晶相，而粒子取向表现出类似玻璃的动力学，没有长程有序。通过布朗动力学模拟，我们证明剪切可以引发从具有取向无序的各向同性晶体到沿剪切方向具有片层的取向有序晶体的相变。这种非平衡转变伴随着遵循成核和生长机制的取向有序化。通过对自由能分析进行唯象扩展，我们揭示成核源于剪切引起的取向涨落。通过开发具有无记忆状态函数的晶格模型，研究发现取向结晶簇的生长呈盘状。这些发现为非平衡态下各向异性粒子有序转变的机制带来了新的见解。
