Porous amorphous silica (a-SiO₂) is of both fundamental and practical interests, as they exhibit a large specific surface area and tunable porous network. However, the brittle nature of a-SiO₂ and the presence of pre-existing cracks at both micro- and nano-scales lead to complex mechanical behavior. In this study, we systematically investigate the effects of pre-existing crack and its orientation on the mechanical properties of a-SiO₂ with varying pore shapes using reactive molecular dynamics simulations. We demonstrate that pore shape will primarily influence the Young’s modulus (E) and critical energy release rate ($G_{\mathrm{IC}}$). We further investigate the impact of pore shape and crack orientation by local characterization of the structural parameters. By defining the high stress and inter-mediate regions, the overall mechanical properties are found to be greatly influenced by the pore shape which can be reflected through the spatial distribution of von Mises stress. Overall, $G_{\mathrm{IC}}$ is found to increase with the increase of ligament length (also known as pore wall thickness). Meanwhile, the effect of the pre-existing crack on the crack propagation process is confirmed by analyzing the density distribution evolution. These results highlight the interplay between pore morphology and crack orientation in controlling the fracture behaviors in brittle porous materials.

多孔无定形二氧化硅（a-SiO ₂）具有基本的比表面积和实用性，因为它们具有较大的比表面积和可调的多孔网络。然而，a-SiO ₂的脆性以及在微米和纳米尺度上都存在预先存在的裂纹会导致复杂的机械性能。在这项研究中，我们使用反应分子动力学模拟系统地研究了预先存在的裂纹及其取向对具有变化孔形的a-SiO ₂力学性能的影响。我们证明孔的形状将主要影响杨氏模量（E）和临界能量释放率（$G_{\mathrm{我知道了}}$）。我们通过结构参数的局部表征进一步研究孔的形状和裂纹取向的影响。通过定义高应力和中间区域，发现整体机械性能受孔形状的影响很大，孔的形状可以通过冯·米塞斯应力的空间分布反映出来。全面的，$G_{\mathrm{我知道了}}$发现随着韧带长度（也称为孔壁厚度）的增加而增加。同时，通过分析密度分布的演变过程，可以确定预先存在的裂纹对裂纹扩展过程的影响。这些结果突显了在控制脆性多孔材料的断裂行为时，孔隙形态与裂纹取向之间的相互作用。