Molecular dynamics of high pressure reactions in condensed

压力是决定化学反应的选择性、方向和速率的重要物理参数。压力对化学动力学的影响在过去的50年里得到了很好的研究，并收集了大量的实验数据。然而，尽管它们被定性地理解，但由于缺乏足够的理论来定量地解释高压效应，所有这些数据都没有得到充分利用。幸运的是，最近计算机技术的进步似乎为解决这个问题提供了一个适当的工具。 反应机理通常是根据过渡态的性质来讨论的，通过过渡态，反应物转化为产物。传统上，实验测量的压力对反应速率的影响用所谓的活化体积表示，其代表过渡态和反应物体积的差异。由于反应物的体积很容易通过实验获得，因此活化体积提供了过渡态体积的直接测量，从而提供了对这些瞬态物质的独特一瞥。 我们提出了一种计算活化体积的新方法。在我们的方法中，微观反应系统的体积被确定为溶剂中系统的阿基米德位移体积，并且被发现为纯溶剂（N个颗粒）和包含系统的溶剂（N+1个颗粒）的体积之间的差。初步结果表明，体积计算精度较高。

Pressure is an important physical parameter that determines selectivity, direction, and rates of chemical reactions. The effects of pressure on chemical kinetics are well studied and a vast amount of experimental data has been collected over the last fifty years. However, although they are qualitatively understood, all these data are greatly underutilized because of the lack of an adequate theory that accounts quantitatively for high-pressure effects. Fortunately, the recent advancement of computer technology seems to provide a proper instrument for tackling this problem.    Reaction mechanisms are usually discussed in terms of properties of transient states (transition states), through which reactants transform into products. Traditionally, the experimentally measured effects of pressure on reaction rates are expressed in terms of so-called volumes of activation, which represent the difference in volumes of transition states and reactants. Since the volumes of reactants are readily available experimentally, the volumes of activation provide a direct measure of the transition state volumes and thus a unique glimpse at these transient species.    We propose a new method for calculating activation volumes. Within our approach, the volume of a microscopic reaction system is determined as an Archimedean displacement volume of the system in a solvent and is found as a difference between the volumes of the pure solvent (N particles) and the solvent containing the system (N+1 particles). Preliminary results indicate that the volumes can be calculated with high precision.