Svaneborg Carsten, Everaers Ralf
University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
ENSL, CNRS, Laboratoire de Physique and Centre Blaise Pascal de l'École Normale Supérieure de Lyon, F-69342 Lyon, France.
J Chem Phys. 2023 Feb 7;158(5):054903. doi: 10.1063/5.0123431.
We present a computationally efficient multiscale method for preparing equilibrated, isotropic long-chain model polymer melts. As an application, we generate Kremer-Grest melts of 1000 chains with 200 entanglements and 25 000-2000 beads/chain, which cover the experimentally relevant bending rigidities up to and beyond the limit of the isotropic-nematic transition. In the first step, we employ Monte Carlo simulations of a lattice model to equilibrate the large-scale chain structure above the tube scale while ensuring a spatially homogeneous density distribution. We then use theoretical insight from a constrained mode tube model to introduce the bead degrees of freedom together with random walk conformational statistics all the way down to the Kuhn scale of the chains. This is followed by a sequence of simulations with carefully parameterized force-capped bead-spring models, which slowly introduce the local bead packing while reproducing the larger-scale chain statistics of the target Kremer-Grest system at all levels of force-capping. Finally, we can switch to the full Kremer-Grest model without perturbing the structure. The resulting chain statistics is in excellent agreement with literature results on all length scales accessible in brute-force simulations of shorter chains.
我们提出了一种计算效率高的多尺度方法，用于制备平衡的、各向同性的长链模型聚合物熔体。作为一个应用，我们生成了具有200个缠结和每条链25000 - 2000个珠子的Kremer - Grest熔体，其涵盖了直至并超过各向同性 - 向列相转变极限的实验相关弯曲刚度。在第一步中，我们采用晶格模型的蒙特卡罗模拟来平衡管尺度以上的大规模链结构，同时确保空间均匀的密度分布。然后，我们利用约束模式管模型的理论见解，引入珠子自由度以及随机游走构象统计，直至链的库恩尺度。接下来是一系列使用精心参数化的力帽珠子 - 弹簧模型的模拟，这些模拟在所有力帽水平上缓慢引入局部珠子堆积，同时再现目标Kremer - Grest系统的更大尺度链统计。最后，我们可以切换到完整的Kremer - Grest模型而不干扰结构。所得的链统计在短链的暴力模拟可及的所有长度尺度上与文献结果高度一致。
