van der Meer Berend, Smallenburg Frank, Dijkstra Marjolein, Filion Laura
Soft Condensed Matter, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands.
Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France.
Soft Matter. 2020 May 6;16(17):4155-4161. doi: 10.1039/d0sm00335b.
Binary mixtures of hard spheres can spontaneously self-assemble into binary crystals. Computer simulations have been especially useful in mapping out the phase behaviour of these mixtures, under the assumption that the stoichiometry of the binary crystal is ideal. Here we show that for a size ratio of q = 0.82 this assumption is not valid near the coexistence region between the fluid and the stable binary crystal, the MgZn2 Laves phase. Instead we find a surprisingly high number of antisite defects: up to 2% of the large spheres are replaced by small spheres in equilibrium. We demonstrate that the defect concentration can be estimated using simple approximations, providing an easy way to identify systems where antisite defects play an important role. Our results shed new light on the self-assembly of colloidal Laves phases, and demonstrate the importance of antisite defects in binary crystals.
硬球二元混合物能够自发地自组装成二元晶体。在二元晶体化学计量比为理想状态的假设下，计算机模拟对于描绘这些混合物的相行为特别有用。在此我们表明，对于尺寸比q = 0.82的情况，在流体与稳定二元晶体（MgZn₂拉弗斯相）之间的共存区域附近，该假设是无效的。相反，我们发现了数量惊人的反位缺陷：在平衡状态下，高达2%的大球被小球取代。我们证明，可以使用简单近似来估计缺陷浓度，这为识别反位缺陷起重要作用的系统提供了一种简便方法。我们的结果为胶体拉弗斯相的自组装提供了新的见解，并证明了反位缺陷在二元晶体中的重要性。
