Nguyen Van Duc, Hu Zhibing, Schall Peter
Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, NL-1098 XH Amsterdam, The Netherlands.
Phys Rev E Stat Nonlin Soft Matter Phys. 2011 Jul;84(1 Pt 1):011607. doi: 10.1103/PhysRevE.84.011607. Epub 2011 Jul 15.
We measure the anisotropy of the crystal-fluid interfacial free energy in soft colloidal systems. A temperature gradient is used to direct crystal nucleation and control the growth of large single crystals in order to achieve well-equilibrated crystal-fluid interfaces. Confocal microscopy is used to follow both the growth process and the equilibrium crystal-fluid interface at the particle scale: heterogeneous crystal nucleation, the advancing interface, and the stationary equilibrium interface. We use the measured growth velocity to determine the chemical potential difference between crystal and fluid phases. Well-equilibrated, large crystal-fluid interfaces are then used to determine the interfacial free energy and its anisotropy directly from thermally excited interface fluctuations. We find that while the measured average interfacial free energy is in good agreement with values found in simulations, the anisotropy is significantly larger than simulation values. Finally, we investigate the effect of impurities on the advancing interface. We determine the critical force needed to overcome impurity particles from the local interface curvature.
我们测量了软胶体系统中晶体 - 流体界面自由能的各向异性。利用温度梯度来引导晶体成核并控制大单晶的生长，以实现平衡良好的晶体 - 流体界面。共聚焦显微镜用于在粒子尺度上跟踪生长过程和平衡晶体 - 流体界面：异质晶体成核、前进界面和静态平衡界面。我们利用测量的生长速度来确定晶体相和流体相之间的化学势差。然后，利用平衡良好的大晶体 - 流体界面，直接从热激发的界面涨落中确定界面自由能及其各向异性。我们发现，虽然测量的平均界面自由能与模拟值吻合良好，但各向异性明显大于模拟值。最后，我们研究了杂质对前进界面的影响。我们从局部界面曲率确定克服杂质颗粒所需的临界力。
