Persistence Length, End-to-End Distance, and Structure of Coarse-Grained Polymers
Persistence Length, End-to-End Distance, and Structure of Coarse-Grained Polymers
复制标题
DOI：
10.1021/acs.jctc.7b01229
复制
发表时间：
2018-04-01
影响因子：
5.5
通讯作者：
Bernstein, Noam
中科院分区：
文献类型：
--
作者：
Salerno, K. Michael;Bernstein, Noam
与全原子(AA)分子动力学模拟相比，粗粒(CG)聚合物模拟可以获得更长的时间和更长的长度；然而，并不是所有的CG模型都正确地在所有长度尺度上再现聚合物的性质。在这里，我们通过在单个CG珠子中结合A主链碳原子，从聚乙烯(PE)和聚四氟乙烯(PTFE)熔体模拟中获得粗晶原子位置数据。由此产生的CG变量沿着链主干具有依赖于粗粒化尺度A的相关性，并且通常不通过独立的键长、键角和扭角分布来再现。通过构造与模拟CG势等价的CG变量分布，我们能够以较低的计算代价评估不同CG模型的键取向关联。只包含非键、键长和键角相互作用的CG模型和势，正确地再现了CG变量分布，但不一定再现链的刚性，高估了持续长度L-p和末端到末端的距离<；R-2>；(1/2)。虽然包含独立扭转角的CG模型与键-取向关联相匹配，并且<；R-2>；(1/2)更好，但只有包含键和扭转角之间关联的近似模型才与真实的键-取向关联匹配。
Coarse-grained (CG) polymer simulations can access longer times and larger lengths than all-atom (AA) molecular dynamics simulations; however, not all CG models correctly reproduce polymer properties on all length scales. Here we coarse-grain atomistic position data from polyethylene (PE) and polytetrafluoroethylene (PTFE) melt simulations by combining A backbone carbon atoms in a single CG bead. Resulting CG variables have correlations along the chain backbone that depend on the coarse-graining scale A and are generally not reproduced by independent bond-length, bond-angle and torsion-angle distributions. By constructing distributions of CG variables equivalent to those from simulated CG potentials we are able to evaluate the bond orientation correlation for different CG models at reduced computational cost. CG models and potentials that include only nonbonded, bond-length, and bond-angle interactions computed by Boltzmann inversion correctly reproduce the CG variable distributions but do not necessarily reproduce the chain stiffness, overestimating the persistence length L-p and end-to-end distance < R-2 >(1/2) with increasing lambda. While CG models that include an independent torsion angle match the bond-orientation correlation and < R-2 >(1/2) better, only approximate models that include correlations between bond and torsion angles match the true bond-orientation correlation.