Xu Guoqing, Huang Tao, Han Yilong, Chen Yong
Center of Soft Matter Physics and Its Applications, Beihang University, Beijing 100191, China.
School of Physics, Beihang University, Beijing 100191, China.
Soft Matter. 2022 Nov 30;18(46):8830-8839. doi: 10.1039/d2sm00783e.
Active matter exhibits various collective motions and nonequilibrium phases, such as crystals; however, their surface properties have been poorly explored. Here, we use Brownian dynamics simulations to investigate the surface morphology and dynamics of two-dimensional active crystals during and after growth. For crystal growth on a substrate, the position and roughness of the crystal surface reach steady states at different times. In the steady state, the surface exhibits superdiffusive behaviour at the short time, and the roughness is insensitive to the roughening process and particle activity. We observe two-stage and three-stage surface roughening at different Péclet numbers. The result of dynamic scaling analysis shows that the surface is similar to anomalous roughening, which is distinct from the normal roughening typically found in conventional passive systems. Capillary wave theory for a thermal equilibrium system can describe the active surface fluctuations only in the long-wavelength regime, indicating that active particles mainly drive the surface out of equilibrium locally. These similarities and differences between the active and passive crystal surfaces are essential for understanding active crystals and interfaces.
活性物质表现出各种集体运动和非平衡相，如晶体；然而，它们的表面性质尚未得到充分研究。在这里，我们使用布朗动力学模拟来研究二维活性晶体生长过程中和生长后的表面形态和动力学。对于在基底上的晶体生长，晶体表面的位置和粗糙度在不同时间达到稳态。在稳态下，表面在短时间内表现出超扩散行为，并且粗糙度对粗化过程和粒子活性不敏感。我们在不同的佩克莱数下观察到两阶段和三阶段的表面粗化。动态标度分析结果表明，表面类似于反常粗化，这与传统被动系统中通常发现的正常粗化不同。热平衡系统的毛细波理论只能描述长波长范围内的活性表面涨落，这表明活性粒子主要在局部驱动表面偏离平衡。活性和被动晶体表面之间的这些异同对于理解活性晶体和界面至关重要。
