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首页> 外文期刊>The Journal of Chemical Physics >The short-time dynamics of molecular reorientation in liquids. I. The instantaneous generalized Langevin equation [Review]
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The short-time dynamics of molecular reorientation in liquids. I. The instantaneous generalized Langevin equation [Review]

机译：液体中分子重新定向的短期动态。一，瞬时广义朗文方程[综述]

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Up until relatively recently, experimental measurements of the rotational dynamics of small molecules in liquids were largely confined to seeing the effects of rotational diffusion. The molecular character of the process seemed of little relevance. However, newer measurements have begun to look in some detail at the microscopics behind molecular reorientation. We show in this paper that it is possible to understand the short-time dynamics of rotation in liquids at a molecular level by looking at the instantaneous normal modes of the remaining degrees of freedom. With the aid of some other, properly short-time, approximations, the reorientational dynamics can be cast into the form of an instantaneous generalized Langevin equation-one defined for each liquid configuration. One therefore obtains fully molecular expressions for the instantaneous rotational friction and fluctuating torque felt by a solute. The average friction so obtained seems to describe the basic nondiffusional aspects of rotation reasonably accurately and lends itself-as we illustrate in the companion paper-to more detailed investigations into the actual molecular mechanisms behind rotational relaxation. In the course of this work we also show that just as the autocorrelation function for the force on a rigid bond yields an accurate portrayal of the friction needed to study vibrational relaxation, quantitatively accurate results for the rotational friction can be provided by using molecular dynamics to compute the torque autocorrelation function for an orientationally rigid solute. (C) 2000 American Institute of Physics. [S0021-9606(00)50217-7]. [References: 113]
机译：直到最近，对液体中小分子旋转动力学的实验测量还主要局限于观察旋转扩散的影响。该过程的分子特征似乎无关紧要。然而，新的测量方法已经开始在分子重新定向背后的显微镜下更加详细地观察。我们在本文中表明，可以通过观察剩余自由度的瞬时正常模式来了解分子水平上液体中旋转的短时动力学。借助其他适当的短时近似，可以将重新定向动力学转换为瞬时广义Langevin方程的形式-为每种液体配置定义一个。因此，人们获得了由溶质感受到的瞬时旋转摩擦和波动扭矩的完整分子表达式。如此获得的平均摩擦似乎可以合理准确地描述旋转的基本非扩散方面，并且如我们在随附文件中所说明的那样，很适合对旋转松弛背后的实际分子机理进行更详细的研究。在这项工作的过程中，我们还表明，正如刚性键上力的自相关函数可以精确地描述研究振动松弛所需的摩擦力一样，可以通过使用分子动力学来提供旋转​​摩擦的定量精确结果。计算定向刚性溶质的转矩自相关函数。 （C）2000美国物理研究所。 [S0021-9606（00）50217-7]。 [参考：113]

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