A new off‐lattice Monte Carlo model for polymers: A comparison of static and dynamic properties with the bond‐fluctuation model and application to random media
A new off‐lattice Monte Carlo model for polymers: A comparison of static and dynamic properties with the bond‐fluctuation model and application to random media
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聚合物的新离格蒙特卡罗模型：静态和动态特性与键涨落模型的比较及其在随机介质中的应用
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发表时间：
1993
期刊：
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通讯作者：
W. Paul
中科院分区：
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作者：
I. Gerroff;A. Milchev;K. Binder;W. Paul
采用链长为N=64、单体数为16 384个的多链聚合物体系，采用链接单元蒙特卡罗方法研究了三维连续空间中的多链聚合物体系模型。链由具有硬核的珠子组成，这些珠子由相当坚硬的谐波键连接，珠子之间的相互作用是排斥性的Lennard - Jones型相互作用，使得链在随机运动中不能相互交叉。在RISC工作站上，该模型仅比键波动晶格模型慢约4倍，时间相关均方位移和松弛函数的定性行为与后者非常相似。对于无障碍模型，通过适当调整链长和体积分数，可以近似地映射到晶格键波动模型上。但目前模型的独特优势在于，它可以很容易地应用于随机介质（由随机放置的刚性障碍物描述），而不会出现这种系统的晶格模型中出现的严重遍历问题（锁定构型）。结果表明，链的静态特性几乎不受障碍物的影响，而链的运动在这种冰冻环境中大大减缓。
A model for a multichain polymer system in three‐dimensional continuous space is studied by link cell Monte Carlo methods, using systems up to chain length N=64 and up to 16 384 monomers. The chains consist of beads with a hard core connected by rather stiff harmonic bonds, with a repulsive Lennard‐Jones‐type interaction between beads chosen such that chains cannot cross each other during their random motions. On RISC workstations the model performs only about a factor of 4 slower than the bond fluctuation lattice model, the qualitative behavior of the time‐dependent mean‐square displacements and relaxation functions being rather similar to the latter. For the model without obstacles, it is shown that the present continuum model can be approximately mapped on the lattice bond fluctuation model by a suitable rescaling of chain length and volume fraction. But the distinctive advantage of the present model is that it can be applied easily to random media (described by randomly placed rigid obstacles), without the severe ergodicity problems (locked‐in configurations) arising in lattice models for such systems. It is shown that static properties of the chains stay nearly unaffected by the obstacles, while the chain motions are considerably slowed down in this frozen environment.