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

堪萨斯大学的Ward Thompson获得了化学系化学理论、模型和计算方法项目的奖励，以开发预测化学系统中动力学对温度依赖性的方法。在实验室或工业环境中，改变这些外部性质是控制化学反应的关键方法。因此，了解这些变量如何影响化学过程中重要运动的时间尺度是很重要的。这些知识还提供了对决定时间尺度的分子水平运动的见解。例如，在这个项目中开发的方法允许在单一温度下通过模拟直接计算任何时间尺度（如化学反应发生的时间）的温度依赖性。同时，它们提供了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。除了随温度变化的性能外，还可以计算其他性能（如压力或系统成分）的影响。虽然这些方法适用于任何化学系统，但汤普森团队专注于液体动力学。该奖项还支持一项面向小学生的拓展计划，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是做什么的，并鼓励他们通过与研究生和教师的活动和互动，将自己视为科学家。所开发的方法分为三类：1)在单一温度下通过模拟计算反应和其他动力学过程的活化能。这些方法提供了其他无法获得的信息：不同的相互作用对活化能的贡献。2)评价温度以外的物理条件（如压力或化学势）对动态时间尺度变化的影响。这使得在单一压力下模拟的激活体积等数据成为可能。3)计算速率常数和其他动态时间尺度相对于底层哈密顿量（如质量或势参数）分量的导数的方法，以深入了解机制、力场和动力学同位素效应。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识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.