Pangburn Todd O, Bevan Michael A
Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843-3122, USA.
J Chem Phys. 2005 Nov 1;123(17):174904. doi: 10.1063/1.2074887.
In this paper, we investigate the effects of using inverse analyses developed for monodisperse particles to extract particle-particle and particle-surface potentials from simulated interfacial colloidal configurations having finite-size polydispersity. Forward Monte Carlo simulations are used to generate three-dimensional equilibrium configurations of log normal-distributed polydisperse particles confined by gravity near an underlying surface. Particles remain levitated above the substrate and stabilized against aggregation by repulsive electrostatic Derjaguin-Landau-Verwey-Overbeek pair potentials. An inverse Ornstein-Zernike analysis and an inverse Monte Carlo simulation method are used to obtain interactions from simulated distribution functions as a function of polydispersity (sigma), relative range of repulsion (kappa a), and projected interfacial concentration (rho). Both inverse analyses successfully recover input potentials for all monodisperse cases, but fail for polydispersities often encountered in experiments. For different conditions (sigma, kappa a, and rho), our results indicate softened short-range repulsion, anomalous long-range attraction, and apparent particle overlaps, which are similar to commonly reported observations in optical microscopy measurements of quasi-two-dimensional interfacial colloidal ensembles. By demonstrating signatures of, and limitations due to, polydispersity when extracting pair potentials from measured distribution functions, our specific goal is to provide a basis to objectively interpret and resolve the effects of polydispersity in optical microscopy experiments.
在本文中，我们研究了使用为单分散颗粒开发的反演分析方法，从具有有限尺寸多分散性的模拟界面胶体构型中提取颗粒间和颗粒-表面势能的效果。正向蒙特卡罗模拟用于生成由重力限制在下层表面附近的对数正态分布多分散颗粒的三维平衡构型。颗粒保持悬浮在基底上方，并通过排斥性静电德亚金-朗道-韦弗-奥弗贝克对势来稳定以防止聚集。使用反演奥恩斯坦-泽尔尼克分析和反演蒙特卡罗模拟方法，从模拟分布函数中获取作为多分散性（σ）、相对排斥范围（κa）和投影界面浓度（ρ）函数的相互作用。两种反演分析在所有单分散情况下都成功恢复了输入势能，但在实验中经常遇到的多分散性情况下却失败了。对于不同条件（σ、κa和ρ），我们的结果表明短程排斥软化、长程异常吸引以及明显的颗粒重叠，这与在准二维界面胶体集合体的光学显微镜测量中通常报道的观察结果相似。通过展示从测量分布函数中提取对势时多分散性的特征和局限性，我们的具体目标是为客观解释和解决光学显微镜实验中多分散性效应提供基础。
