Dynamics of Rigid and Flexible Constraints for Polymers. Effect of the Fixman Potential
Dynamics of Rigid and Flexible Constraints for Polymers. Effect of the Fixman Potential
复制标题
聚合物刚性和柔性约束的动力学。
DOI：
10.1021/ma00145a036
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发表时间：
1985
期刊：
影响因子：
5.5
通讯作者：
R. Yaris
中科院分区：
文献类型：
--
作者：
D. Perchak;J. Skolnick;R. Yaris
聚合物的模型通常可以分为两类：（a）柔性的，其中键长和价角被强调和势约束到几乎恒定的值，和（B）刚性的，其中约束B是几何的，即，固定键长和键角。一般来说，这些系统的统计力学是不同的。通过引入基于无约束坐标的度量行列式的补偿势（Fixman势），使刚性模型再现平衡柔性结果。目前尚不清楚是否也再现了相应的动态。本文研究了Fixman势对系统动力学的影响。我们已经进行了布朗动力学模拟的三种模型的正丁烷类分子：柔性，刚性，刚性加Fixman潜力。结果表明，对于某些自相关函数的二面角，有一个明确的，虽然很小，刚性和柔性模型之间的动力学差异在低摩擦极限。在高摩擦下，差异减小，动力学基本相同。在这两种情况下，Fixman势的影响都很小。
Models of polymers can generally be divided into two classes: (a) flexible, wherein bond lengths and valence angles are constrained to nearly constant values by strong, harmonic potentials, and (b) rigid, wherein the constrainb are geometric, Le., fixed bond lengths and angles. In general, the statistical mechanics of such systems differ. By introduction of a compensating potential based on the metric determinant of the unconstrained coordinates (the Fixman potential), the rigid model can be made to reproduce the equilibrium flexible results. It is not clear whether the corresponding dynamics are also reproduced. The purpose of the present work is to investigate the effect of the Fixman potential on dynamics. We have performed Brownian dynamics simulations of three models of a n-butane-like molecule: flexible, rigid, and rigid-plus-Fixman potential. Results show that for certain autocorrelation functions of the dihedral angle, there is a definite, though small, difference in dynamics between the rigid and flexible models in the low-friction limit. At high friction the difference has decreased and the dynamics are essentially the same. The effect of the Fixman potential is minimal in both cases.