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采用分子动力学的方法研究二氧化硅表面二氧化碳的结构和扩散性质。二氧化碳在二氧化硅固体表面形成高密度层;而在远离固体表面处,流体的密度分布类似于宏观二氧化碳,取向分布比较随机。受固体表面的影响,二氧化碳的C-C径向分布函数第一峰的高度比宏观二氧化碳高。二氧化碳的密度分布和自由能分布有一明显的“镜面对称”的结构,高密度区域对应自由能的深阱。二氧化硅中的二氧化碳的自扩散行为是各向异性的,z方向的扩散由于固体面的作用明显受阻。由取向相关函数积分得到的二氧化硅表面流体的取向相关时间比宏观流体大的多,二氧化碳分子在固体表面再定位比较缓慢。
The structure and diffusion properties of carbon dioxide on silica surface were investigated by molecular dynamics method. Carbon dioxide forms a high-density layer on the surface of silica solid, while at a distance from the solid surface, the density distribution of the fluid is similar to that of macro-carbon dioxide, and the orientation distribution is relatively random. Affected by the solid surface, the C-C radial distribution of carbon dioxide has a higher first peak height than macro-carbon dioxide. The density distribution and free energy distribution of carbon dioxide have a clear “mirror symmetry ” structure, high density region corresponds to the deep well of free energy. The self-diffusion of carbon dioxide in silica is anisotropic, and the diffusion in the z-direction is significantly obstructed by the effect of the solid surface. The orientation time of the silica surface fluid integrated by the orientation correlation function is much larger than that of the macroscopic fluid, and the carbon molecules are reoriented relatively slowly on the solid surface.