Departamento de Física Aplicada, Cinvestav-Mérida, AP 73 "Cordemex," 97310 Mérida, Yucatán, Mexico.
Departamento de Ingeniería Física, División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, 37150 León, Guanajuato, Mexico.
J Chem Phys. 2022 Aug 21;157(7):074903. doi: 10.1063/5.0099919.
Depletion forces are fundamental for determining the phase behavior of a vast number of materials and colloidal dispersions and have been used for the manipulation of in- and out-of-equilibrium thermodynamic states. The entropic nature of depletion forces is well understood; however, most theoretical approaches, and also molecular simulations, work quantitatively at moderate size ratios in much diluted systems since large size asymmetries and high particle concentrations are difficult to deal with. The existing approaches for integrating out the degrees of freedom of the depletant species may fail under these extreme physical conditions. Thus, the main goal of this contribution is to introduce a general physical formulation for obtaining the depletion forces even in those cases where the concentration of all species is relevant. We show that the contraction of the bare forces uniquely determines depletion interactions. Our formulation is tested by studying depletion forces in binary and ternary colloidal mixtures. We report here results for dense systems with total packing fractions of 45% and 55%. Our results open up the possibility of finding an efficient route to determine effective interactions at a finite concentration, even under non-equilibrium thermodynamic conditions.
耗散力对于确定大量材料和胶体分散体的相行为至关重要，并且已经被用于操纵平衡和非平衡热力学状态。耗散力的熵性质已被很好地理解；然而，由于大的尺寸不对称和高粒子浓度难以处理，大多数理论方法以及分子模拟在适度的尺寸比和高度稀释的系统中定量工作。在这些极端物理条件下，排除消耗物种自由度的现有方法可能会失败。因此，这项工作的主要目标是引入一种通用的物理公式，即使在所有物种浓度都相关的情况下，也可以获得耗散力。我们表明，裸力的收缩唯一地决定了耗散相互作用。我们的公式通过研究二元和三元胶体混合物中的耗散力进行了测试。我们报告了总堆积分数为 45%和 55%的密集系统的结果。我们的结果为在有限浓度下确定有效相互作用开辟了可能性，即使在非平衡热力学条件下也是如此。
