Department of Materials Science and Engineering, The University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, United Kingdom.
J Chem Phys. 2012 Aug 14;137(6):064116. doi: 10.1063/1.4742187.
We present the results obtained from a systematic equilibrium molecular dynamics study of the effect of torsional flexibility on the diffusion and viscosity of a series of linear alkanes. To make unambiguous comparisons between molecules with torsional flexibility and those without, we use the frozen distribution sampling (FDS) method introduced by Travis et al. [J. Chem. Phys. 98, 1524 (1993); J. Chem. Phys. 102, 2174 (1995)] but modified and updated for increased efficiency. We first demonstrate comprehensively that FDS guarantees corresponding thermodynamic states. We then show that removal of torsional flexibility results in a significant lowering of the diffusion coefficient (and corresponding increase in shear viscosity) and furthermore that this effect increases with increasing chain length. The results are discussed in terms of the possible mechanism giving rise to this dynamic coupling phenomenon.
我们呈现了通过系统平衡分子动力学研究扭转灵活性对一系列线性烷烃扩散和粘度的影响所得到的结果。为了在具有扭转灵活性的分子和没有扭转灵活性的分子之间进行明确的比较，我们使用了 Travis 等人引入的冻结分布采样（FDS）方法[J. Chem. Phys. 98, 1524 (1993); J. Chem. Phys. 102, 2174 (1995)]，但进行了修改和更新以提高效率。我们首先全面证明了 FDS 保证了相应的热力学状态。然后我们表明，去除扭转灵活性会导致扩散系数显著降低（并相应地剪切粘度增加），而且这种影响随着链长的增加而增加。结果根据导致这种动态耦合现象的可能机制进行了讨论。
