Trisilanol polyhedral oligomeric silsesquioxane (POSS) are a category of inorganic–organic material that comprise an inorganic open cage silica structure, organic attachments, and silanol (SiOH) groups. Recently, trisilanol POSS was added to Al-based alloys, and found to promote substantial microstructural refinement, and improved mechanical strength and fatigue life compared to conventional compositions. Such microstructural modifications and property enhancements are usually attributed to silanolAl bonds that formed within the liquid-state, prior to solidification. However, details of such high-temperature chemical interactions remain unclear. Here, we performed molecular dynamics simulations at 1500 K, to probe the chemical interactions between isolated trisilanol POSS molecule and discreet Al atoms. Al atoms modified the silanol groups to form, two energetically favorable coordinate complexes: monodentate SiOAl and bidentate (SiO)Al. Such complexes were formed by Al atoms attracting electrons towards themselves from the POSS molecule. Crucially, this bonding mechanism allowed trisilanol POSS to organize the neighboring Al atoms into geometric motifs that can potentially serve as nucleation sites within liquid-Al, and facilitate microstructural refinement.

中文翻译：

---

分离的多面体低聚倍半硅氧烷三硅烷醇与铝之间相互作用的从头算分子动力学研究

三硅烷醇多面体低聚倍半硅氧烷（POSS）是一类无机-有机材料，包含无机开笼二氧化硅结构、有机附着物和硅烷醇（SiOH）基团。最近，三硅醇 POSS 被添加到铝合金中，与传统成分相比，发现可显着细化微观结构，并提高机械强度和疲劳寿命。这种微观结构的改变和性能的增强通常归因于凝固之前在液态内形成的硅醇铝键。然而，这种高温化学相互作用的细节仍不清楚。在这里，我们在 1500 K 下进行了分子动力学模拟，以探讨孤立的三硅烷醇 POSS 分子和离散的 Al 原子之间的化学相互作用。 Al 原子修饰硅烷醇基团，形成两种能量上有利的配位络合物：单齿 SiOAl 和二齿 (SiO)Al。这种复合物是由 Al 原子从 POSS 分子吸引电子而形成的。至关重要的是，这种键合机制使三硅烷醇 POSS 将相邻的铝原子组织成几何图案，这些图案可以作为液态铝内的成核位点，并促进微观结构的细化。