The transient (or permanent) structural modifications which occur during local deformation of oxide glasses are typically studied on the basis of short-range data, for example, obtained through vibrational spectroscopy. This is in contrast to macroscopic observations, where variations in material density can usually not be explained using next-neighbor correlations alone. Recent experiments employing low-frequency Raman spectroscopy have pointed-out this issue, emphasizing that the deformation behavior of glasses is mediated through structural heterogeneity and drawing an analogy to granular media. Here, we provide additional support to this understanding, using an alternative experimental method. Structural modification of vitreous silica in the stress field of a sharp diamond indenter tip was monitored by in-situ small-angle X-ray scattering. The influenced zone during loading and after unloading was compared, demonstrating that changes in the position of the first sharp diffraction peak (FSDP) directly in the center of the indent are of permanent character. On the other hand, variations in the amplitude of electron density fluctuations (AEDF) appear to fully recover after load release. The lateral extent of the modifications and their relaxation are related to the short- to intermediate-range structure and elastic heterogeneity pertinent to the glass network. With support from Finite Element Analysis, we suggest that different structural length scales govern shear deformation and isotropic compaction in vitreous silica.

通常基于例如通过振动光谱法获得的短程数据来研究在氧化物玻璃的局部变形期间发生的瞬时（或永久）结构改变。这与宏观观察相反，在宏观观察中，通常不能仅使用邻域相关性来解释材料密度的变化。最近使用低频拉曼光谱的实验指出了这个问题，强调玻璃的变形行为是通过结构异质性来介导的，并且类似于颗粒介质。在这里，我们使用替代的实验方法为这种理解提供了额外的支持。玻璃二氧化硅在尖锐的金刚石压头应力场中的结构改变通过监测。原位小角度X射线散射。比较了加载过程中和卸载后的影响区域，表明直接在压痕中心的第一个尖锐衍射峰（FSDP）位置的变化具有永久性。另一方面，负载释放后，电子密度波动（AEDF）的幅度变化似乎已完全恢复。修饰的横向范围及其松弛与玻璃网络相关的短至中程结构和弹性异质性有关。在有限元分析的支持下，我们建议使用不同的结构长度尺度控制玻璃状石英中的剪切变形和各向同性压实。