Data_Sheet_1_Mechanisms of Silica Fracture in Aqueous Electrolyte Solutions.pdf

Glassy silicates are substantially weaker when in contact with aqueous electrolyte solutions than in vacuum due to chemical interactions with preexisting cracks. To investigate this silicate weakening phenomenon, classical molecular dynamics (MD) simulations of silica fracture were performed using the bond-order based, reactive force field ReaxFF. Four different environmental conditions were investigated: vacuum, water, and two salt solutions (1M NaCl, 1M NaOH) that form relatively acidic and basic solutions, respectively. Any aqueous environment weakens the silica, with NaOH additions resulting in the largest decreases in the effective fracture toughness (eKIC) of silica or the loading rate at which the fracture begins to propagate. The basic solution leads to higher surface deprotonation, narrower radius of curvature of the crack tip, and greater weakening of the silica, compared with the more acidic environment. The results from the two different electrolyte solutions correspond to phenomena observed in experiments and provide a unique atomistic insight into how anions alter the chemical-mechanical fracture response of silica.

玻璃态硅酸盐与水性电解质溶液接触时的强度远低于真空环境下的强度，这是由于其与预先存在的裂纹发生了化学相互作用。为研究这一硅酸盐弱化现象，本研究采用基于键序的反应力场ReaxFF，开展了二氧化硅断裂的经典分子动力学（MD）模拟。本研究共考察了四种不同的环境条件：真空、纯水，以及两种盐溶液（1M氯化钠、1M氢氧化钠），二者分别形成偏酸性和偏碱性的溶液环境。所有水性环境均会弱化二氧化硅，其中添加氢氧化钠的环境会使二氧化硅的有效断裂韧性（effective fracture toughness，eKIC）以及裂纹开始扩展的加载速率出现最大幅度的下降。与偏酸性环境相比，碱性环境会使二氧化硅表面发生更高程度的去质子化，裂纹尖端的曲率半径更小，进而对二氧化硅的弱化作用更强。两种电解质溶液的模拟结果与实验中观测到的现象一致，并为揭示阴离子如何改变二氧化硅的化学-机械断裂响应提供了独特的原子尺度视角。