Institute of Mathematics, Department of Mathematical Physics, Ural Federal University, Lenin av. 51, 620000 Ekaterinburg, Russia.
Institute for Computational Physics, Universiät Stuttgart, Allmandring 3, 70569 Stuttgart, Germany.
J Chem Phys. 2013 Dec 14;139(22):224905. doi: 10.1063/1.4834635.
In the present manuscript we develop a theoretical approach to describe the pair correlation function of bidisperse magnetic dipolar hard- and soft-spheres. We choose bidisperse system as the first step to allow for polydispersity when studying thermodynamics of magnetic fluids. Using diagram technique we calculate the virial expansion of the pair correlation function up to the first order in density and fourth order in the dipolar strength. Even though, the radial distribution functions are extremely sensitive to the steric potential, we show that the behaviour of the isotropic centre-centre structure factor is almost indifferent to the type of the short-range repulsion. We extensively compare our theoretical results to the data of molecular dynamics simulations, which helps us to understand the range of validity of the virial expansion both on density and magnetic dipolar strength. We also investigate the influence of the granulometric composition on the height, width, and position of the structure factor first peak in order to clarify whether it is possible to extract structural information from experimentally measured small angle neutron scattering intensities.
在本手稿中，我们开发了一种理论方法来描述双分散磁性偶极硬软球的对关联函数。我们选择双分散系统作为第一步，以便在研究磁性液体的热力学时考虑多分散性。使用图论技术，我们计算了对关联函数的 virial 展开，直到密度的一阶和偶极强度的四阶。尽管如此，径向分布函数对位阻势极其敏感，但我们表明各向同性中心-中心结构因子的行为几乎不受短程排斥类型的影响。我们广泛地将我们的理论结果与分子动力学模拟的数据进行比较，这有助于我们理解 virial 展开在密度和磁偶极强度上的有效性范围。我们还研究了粒度组成对结构因子第一峰的高度、宽度和位置的影响，以澄清是否可以从实验测量的小角度中子散射强度中提取结构信息。
