Alhissi Mohammed, Zumbusch Andreas, Fuchs Matthias
Fachbereich Physik, Universität Konstanz, 78464 Konstanz, Germany.
Fachbereich Chemie, Universität Konstanz, 78464 Konstanz, Germany.
J Chem Phys. 2024 Apr 28;160(16). doi: 10.1063/5.0196599.
Molecular anisotropy plays an important role in the glass transition of a liquid. Recently, a novel bulk glass state has been discovered by optical microscopy experiments on suspensions of ellipsoidal colloids. "Liquid glass" is a disordered analog of a nematic liquid crystal, in which rotation motion is hindered but particles diffuse freely. Global nematic order is suppressed as clusters of aligned particles intertwine. We perform Brownian dynamics simulations to test the structure and dynamics of a dense system of soft ellipsoidal particles. As seen in the experiments and in accordance with predictions from the mode coupling theory, on the time scale of our simulations, rotation motion is frozen but translation motion persists in liquid glass. Analyses of the dynamic structure functions for translation and rotation corroborates the presence of two separate glass transitions for rotation and translation, respectively. Even though the equilibrium state should be nematic, aligned structures remain small and orientational order rapidly decays with increasing size. Long-wavelength fluctuations are remnants of the isotropic-nematic transition.
分子各向异性在液体的玻璃化转变中起着重要作用。最近，通过对椭球形胶体悬浮液进行光学显微镜实验发现了一种新型的块状玻璃态。“液体玻璃”是向列型液晶的无序类似物，其中旋转运动受阻但粒子可自由扩散。随着排列粒子簇相互缠绕，整体向列序受到抑制。我们进行布朗动力学模拟以测试软椭球形粒子密集系统的结构和动力学。如实验中所见并符合模式耦合理论的预测，在我们模拟的时间尺度上，旋转运动被冻结但平移运动在液体玻璃中持续存在。对平移和旋转的动态结构函数的分析分别证实了旋转和平移存在两个独立的玻璃化转变。尽管平衡态应为向列型，但排列结构仍然很小且取向序随尺寸增加迅速衰减。长波长涨落是各向同性 - 向列型转变的残余。
