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arXiv 2007.06779cond-mat.soft
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打击乐器-Yevick结构因素简化

Percus-Yevick Structure Factors Made Simple

Robert Botet, Sylvie Kwok, Bernard Cabane

摘要:

通过小角X射线散射测量颗粒分散体的结构因子S(q)提供了一种研究胶体颗粒空间排列的独特方法。然而,不可能从S(q)中找到粒子的确切位置,因为SAXS信号中固有地缺乏一些信息。分析实验结构因子的两种标准方法是将其与从模拟系统计算的结构因子或从近似系统计算的分析结构因子进行比较。对于单分散硬球的液体,后一种方法通过与Percus-Yevick闭合方程一起使用的Ornstein-Zernike方程提供分析结构因子。以这种方式获得的结构因子不足以用于多分散颗粒的更常见的分散体。然而,Vrij,Bloom和Stell能够证明相同的数学框架可以扩展到产生实验结构因子的精确近似值。尽管如此,由于其数学复杂性,这种解决方案仍然没有得到充分利用。在目前的工作中,我们推导和报告的完整的Percus-Yevick解决方案一般多分散硬球系统在一个简洁的形式,是直接使用。解的形式足够简单,可以给出几个重要的粒子半径分布(舒尔茨,截断正态和逆高斯)的现成解。我们还详细讨论了幂律半径分布的情况下,相关的情况下,系统的阿波罗包装的球体,最近发现实验中的高内相比乳液。

英文摘要:

Measuring the structure factor, S(q), of a dispersion of particles by Small-Angle X-ray Scattering provides a unique method to investigate the spatial arrangement of colloidal particles. However, it is impossible to find the exact location of the particles from S(q) because some information is inherently lacking in the SAXS signal. The two standard ways to analyse an experimental structure factor are then to compare it either to structure factors computed from simulated systems, or to analytical structure factors calculated from approximated systems. For liquids of monodisperse hard spheres, the latter method provides analytical structure factors through the Ornstein-Zernike equation used with the Percus-Yevick closure equation. The structure factors obtained in this way were not adequate for the more common dispersions of polydisperse particles. However, Vrij, Bloom and Stell were able to demonstrate that the same mathematical framework could be extended to yield accurate approximations for the experimental structure factor. Still, this solution has remained underused because of its mathematical complexity. In the present work, we derive and report the complete Percus-Yevick solution for general polydisperse hard-spheres systems in a concise form that is straightforward to use. The form of the solution is made simple enough to give ready solutions of several important particle-radius distributions (Schulz, truncated normal and inverse Gaussian). We also discuss in detail the case of the power-law radius distribution, relevant in the case of systems made of an Apollonian packing of spheres, as recently discovered experimentally in high internal-phase-ratio emulsions.

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