Abstract Atomic oxygen erosion is a significant threat to exterior spacecraft polymers. Polyhedral oligomeric silsesquioxane (POSS) is a potential kind of material in resisting AO diffusion erosion, but lack of mechanism studies for application supports. In this research, we used the first-principles calculations to investigate the mechanism based on two types of nominally hydrated POSS named T8 (Si8O12H8) and T10 (Si10O15H10). According to the results, we found that the minimum energy path (MEP) of AO diffusing inside POSS is the adjacent-edge-path rather than the center-path. We also found the energy barriers that hinder the diffusion motion of AO inside POSS are originated from the structural distortion of POSS, which are negatively correlated to Si-O bond length and positively correlated to structural compactness. Thus, compacter POSS structures with shorter Si-O bond length are expected to give better AO diffusion resistance properties.

中文翻译：

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多面体低聚倍半硅氧烷笼内原子氧扩散的第一性原理见解

摘要 原子氧侵蚀是对外部航天器聚合物的重大威胁。多面体低聚倍半硅氧烷 (POSS) 是一种潜在的抗 AO 扩散侵蚀材料，但缺乏应用支持的机理研究。在这项研究中，我们使用第一性原理计算来研究基于两种名义水合 POSS T8 (Si8O12H8) 和 T10 (Si10O15H10) 的机理。根据结果​​，我们发现 POSS 内部 AO 扩散的最小能量路径 (MEP) 是相邻边缘路径而不是中心路径。我们还发现阻碍 AO 在 POSS 内部扩散运动的能垒源于 POSS 的结构畸变，其与 Si-O 键长呈负相关，与结构紧密度呈正相关。因此，