Benzine Omar, Bruns Sebastian, Pan Zhiwen, Durst Karsten, Wondraczek Lothar
Otto Schott Institute of Materials Research University of Jena Fraunhoferstrasse 6 07743 Jena Germany.
Department of Materials Science Physical Metallurgy Technical University of Darmstadt Alarich-Weiss-Straße 2 64287 Darmstadt Germany.
Adv Sci (Weinh). 2018 Aug 29;5(10):1800916. doi: 10.1002/advs.201800916. eCollection 2018 Oct.
Microscopic deformation processes determine defect formation on glass surfaces and, thus, the material's resistance to mechanical failure. While the macroscopic strength of most glasses is not directly dependent on material composition, local deformation and flaw initiation are strongly affected by chemistry and atomic arrangement. Aside from empirical insight, however, the structural origin of the fundamental deformation modes remains largely unknown. Experimental methods that probe parameters on short or intermediate length-scale such as atom-atom or superstructural correlations are typically applied in the absence of alternatives. Drawing on recent experimental advances, spatially resolved Raman spectroscopy is now used in the THz-gap for mapping local changes in the low-frequency vibrational density of states. From direct observation of deformation-induced variations on the characteristic length-scale of molecular heterogeneity, it is revealed that rigidity fluctuation mediates the deformation process of inorganic glasses. Molecular field approximations, which are based solely on the observation of short-range (interatomic) interactions, fail in the prediction of mechanical behavior. Instead, glasses appear to respond to local mechanical contact in a way that is similar to that of granular media with high intergranular cohesion.
微观变形过程决定了玻璃表面缺陷的形成，从而决定了材料对机械失效的抵抗力。虽然大多数玻璃的宏观强度并不直接取决于材料成分，但局部变形和裂纹萌生受到化学和原子排列的强烈影响。然而，除了经验性的认识之外，基本变形模式的结构起源在很大程度上仍然未知。在没有其他选择的情况下，通常会应用探测短或中等长度尺度参数（如原子-原子或超结构相关性）的实验方法。基于最近的实验进展，空间分辨拉曼光谱现在被用于太赫兹间隙，以绘制低频振动态密度的局部变化。通过直接观察分子不均匀性特征长度尺度上的变形诱导变化，发现刚性涨落介导了无机玻璃的变形过程。仅基于短程（原子间）相互作用观察的分子场近似在预测机械行为方面失败了。相反，玻璃似乎以类似于具有高颗粒间内聚力的颗粒介质的方式对局部机械接触做出反应。
