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arXiv 1503.00959cond-mat.soft
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单Polymer体系格子模型的Monte Carlo模拟

Monte Carlo Simulations of Lattice Models for Single Polymer Systems

Hsiao-Ping Hsu

摘要:

用Monte Carlo方法研究了线性高分子链在稀溶液中的行为,并采用了截断的Rosenbluth方法,得到了链长为$N \sim {\cal O}(10^4)$的线性高分子链.基于固定键长的标准简立方晶格模型(SCLM)和键长介于$2$和$\sqrt{10}$之间的键涨落模型(BFM),研究了简立方晶格上的自回避行走(SAW)、无规行走(RWs)和不可逆无规行走(NRRWs)描述的聚合物链的构象.除了柔性链,我们还将我们的研究扩展到由弯曲势控制的不同刚度的半柔性链。从取向相关性提取的链的持久长度估计的所有情况下。我们表明,链的基础上BFM是更灵活的比那些基于SCLM为一个固定的弯曲能量。这两个晶格模型之间的微观差异进行了讨论,并在文献中给出的标度律的理论预测检查和验证。我们的模拟澄清,一个不同的映射比率之间的粗粒度模型和原子现实的描述聚合物是需要在粗粒度的方法,由于不同的交叉渐近行为。

英文摘要:

Single linear polymer chains in dilute solutions under good solvent conditions are studied by Monte Carlo simulations with the pruned-enriched Rosenbluth method up to the chain length $N \sim {\cal O}(10^4)$. Based on the standard simple cubic lattice model (SCLM) with fixed bond length and the bond fluctuation model (BFM) with bond lengths in a range between $2$ and $\sqrt{10}$, we investigate the conformations of polymer chains described by self-avoiding walks (SAWs) on the simple cubic lattice, and by random walks (RWs) and non-reversible random walks (NRRWs) in the absence of excluded volume (EV) interactions. In addition to flexible chains, we also extend our study to semiflexible chains for different stiffness controlled by a bending potential. The persistence lengths of chains extracted from the orientational correlations are estimated for all cases. We show that chains based on the BFM are more flexible than those based on the SCLM for a fixed bending energy. The microscopic differences between these two lattice models are discussed and the theoretical predictions of scaling laws given in the literature are checked and verified. Our simulations clarify that a different mapping ratio between the coarse-grained models and the atomistically realistic description of polymers is required in a coarse-graining approach due to the different crossovers to the asymptotic behavior.

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