Minina Elena S, Blaak Ronald, Kantorovich Sofia S
Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria. Ural Federal University, Lenin av. 51, 620000 Ekaterinburg, Russia.
J Phys Condens Matter. 2018 Apr 11;30(14):145101. doi: 10.1088/1361-648X/aab137. Epub 2018 Feb 21.
In this work, we investigate the pressure and compressibility factors of bidisperse magnetic fluids with relatively weak dipolar interactions and different granulometric compositions. In order to study these properties, we employ the method of diagram expansion, taking into account two possible scenarios: (1) dipolar particles repel each other as hard spheres; (2) the polymer shell on the surface of the particles is modelled through a soft-sphere approximation. The theoretical predictions of the pressure and compressibility factors of bidisperse ferrofluids at different granulometric compositions are supported by data obtained by means of molecular dynamics computer simulations, which we also carried out for these systems. Both theory and simulations reveal that the pressure and compressibility factors decrease with growing dipolar correlations in the system, namely with an increasing fraction of large particles. We also demonstrate that even if dipolar interactions are too weak for any self-assembly to take place, the interparticle correlations lead to a qualitative change in the behaviour of the compressibility factors when compared to that of non-dipolar spheres, making the dependence monotonic.
在这项工作中，我们研究了具有相对较弱偶极相互作用和不同粒度组成的双分散磁性流体的压力和压缩因子。为了研究这些性质，我们采用图解展开法，考虑两种可能的情况：（1）偶极粒子像硬球一样相互排斥；（2）粒子表面的聚合物壳通过软球近似来建模。双分散铁磁流体在不同粒度组成下的压力和压缩因子的理论预测得到了通过分子动力学计算机模拟获得的数据的支持，我们也对这些系统进行了分子动力学模拟。理论和模拟均表明，系统中的压力和压缩因子随着偶极相关性的增加而降低，即随着大颗粒比例的增加而降低。我们还证明，即使偶极相互作用太弱而无法发生任何自组装，与非偶极球体相比，粒子间的相关性也会导致压缩因子行为的定性变化，使这种依赖性变得单调。
