Dipartimento di Fisica, Università dell'Aquila, V. Vetoio 10, Loc. Coppito, I-67100 L'Aquila, Italy.
J Chem Phys. 2012 Jun 14;136(22):224905. doi: 10.1063/1.4728338.
We consider a coarse-grained model in which polymers under good-solvent conditions are represented by soft spheres whose radii, which should be identified with the polymer radii of gyrations, are allowed to fluctuate. The corresponding pair potential depends on the sphere radii. This model is a single-sphere version of the one proposed in Vettorel et al. [Soft Matter 6, 2282 (2010)], and it is sufficiently simple to allow us to determine all potentials accurately from full-monomer simulations of two isolated polymers (zero-density potentials). We find that in the dilute regime (which is the expected validity range of single-sphere coarse-grained models based on zero-density potentials) this model correctly reproduces the density dependence of the radius of gyration. However, for the thermodynamics and the intermolecular structure, the model is largely equivalent to the simpler one in which the sphere radii are fixed to the average value of the radius of gyration and radii-independent potentials are used: for the thermodynamics there is no advantage in considering a fluctuating sphere size.
我们考虑一种粗粒化模型，其中在良溶剂条件下的聚合物由软球表示，其半径（应与回旋半径的聚合物半径相对应）允许波动。相应的对势能取决于球体半径。该模型是 Vettorel 等人提出的模型的单球版本[Soft Matter 6, 2282 (2010)]，它足够简单，可以使我们从两个孤立聚合物（零密度势）的全单体模拟中准确地确定所有势。我们发现，在稀溶液中（基于零密度势的单球粗粒化模型的预期有效范围），该模型正确地再现了回转半径的密度依赖性。然而，对于热力学和分子间结构，该模型在很大程度上等同于更简单的模型，其中球体半径固定为回转半径的平均值，并使用与半径无关的势：对于热力学，考虑波动的球体尺寸没有优势。
