Removing the Barriers to the Calculation of Activation Energies, Activation Volumes, and Mechanistic Insight for Chemical Dynamics

堪萨斯大学的沃德·汤普森得到了化学部化学理论、模型和计算方法项目的支持，以开发预测化学体系中动力学的温度相关性的方法。改变这种外部性质是在实验室或工业环境中控制化学的关键方法。因此，重要的是要了解这些变量如何影响化学中涉及的重要运动的时间尺度。这一知识还提供了对决定时间尺度的分子水平运动的洞察。例如，该项目中开发的方法允许从单一温度下的模拟直接计算任何时间标度(如发生化学反应的时间)的温度依赖性。同时，它们还提供了有关影响温度依赖性的分子相互作用的信息。目前，没有其他方法可以提供这样的信息。除了随温度变化的特性外，还可以计算压力或系统组成等其他性质的影响。虽然这些方法适用于任何化学体系，但汤普森团队专注于液体中的动力学。该奖项还支持一项面向小学生的外展计划，以提高他们对科学的兴趣和动力。它的目的是让学生看到科学家的工作，并通过与研究生和教职员工的活动和互动鼓励他们将自己视为科学家。已开发的方法分为三类：1)那些能够从单一温度下的模拟计算反应和其他动力学过程的活化能的方法。这些方法提供了原本无法获得的信息：不同相互作用对活化能的贡献。2)用物理条件而不是温度，如压力或化学势来评估动态时间尺度的变化。这使得像激活体积这样的量可以在单个压力下从模拟中获得。3)计算速率常数和其他动力学时标相对于基础哈密顿量分量的导数的方法，例如质量或势参数，以深入了解机制、力场和动力学同位素效应。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Ward Thompson of the University of Kansas is supported by an award from the Chemical Theory, Models, and Computational Methods program in the Division of Chemistry to develop methods for predicting the temperature dependence of dynamics in chemical systems. Changing such external properties is a key way to control chemistry in a laboratory or industrial setting. Thus, it is important to understand how these variables affect the timescales of the important motions involved in the chemistry. This knowledge also provides insight into the molecular-level motions that determine the timescale. The methods developed in this project, for example, allow the direct calculation of the temperature dependence of any timescale (such as the time for a chemical reaction to take place) from simulations at a single temperature. At the same time, they give information about the molecular interactions that influence the temperature dependence. Currently, no other method can provide such information. In addition to the behavior with temperature, the effect of other properties such as pressure or system composition may be calculated. While the approaches apply to any chemical system, the Thompson group is focusing on dynamics in liquids. The award also supports an outreach program for elementary school students to increase their interest in and motivation for science. It is designed to let the students see what scientists do and encourage them to view themselves as scientists through activities and interactions with graduate students and faculty. The methods developed fall into three categories: 1) Those enabling the calculation of activation energies for reactions and other dynamical processes from simulations at a single temperature. These approaches provide otherwise unattainable information: the contributions of different interactions to the activation energy. 2) Those evaluating changes in dynamical timescales with physical conditions other than temperature, such as pressure or chemical potential. This makes quantities like the activation volume available from simulations at a single pressure. 3) Approaches for calculating derivatives of rate constants and other dynamical timescales with respect to components of the underlying Hamiltonian, such as masses or potential parameters, to gain insight into mechanisms, force fields, and kinetic isotope effects.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.