Theoretical Studies of Intermolecular Forces

在这个由化学系化学理论、模型和计算方法计划资助的项目中，特拉华大学的Krzysztof Szalewicz教授正在开发理论和计算方法来建模和理解分子间作用力。当两个分子相邻放置时，每个分子都以比将原子结合在一起形成分子的化学力小一个数量级的弱力作用于它的伙伴。许多物理、化学和生物现象都源于这种分子间作用力。分子间力的知识对于解释各种现象是必要的，包括晶体和蛋白质的结构和功能。Szalewicz教授和他的同事们正在开发新的想法，以改进分子间力的建模并扩大其适用范围。预计这项研究将对计量标准、能源勘探、大气建模、了解星际云中的过程、模拟生物现象和预测药物的结晶形态产生影响。这些计算方法是在研究界免费提供的软件中实施的。要预测团簇、生物分子聚集体和凝聚相的性质，需要知道系统的势能面，也称为力场，它描述了分子之间可能的相互取向和分离。这样的表面可以通过对称性适应微扰理论(SAPT)的从头算方法来计算。SAPT提供了一种独特的能力，可以根据导致静电、交换、诱导和色散对相互作用能量的贡献的四种基本物理机制来解释依赖于分子间力的性质。SAPT是基于密度泛函理论(DFT)描述的单体，这种方法被称为SAPT(DFT)，它与常规SAPT一样准确，但速度快得多。Szalewicz教授正在努力进一步发展SAPT，并扩大其适用范围。并努力将SAPT的适用范围扩大到拥有数百个原子的分子，这是朝着基于物理的生物分子力场方向迈出的一步，这可能会将生物分子模拟的可靠性提高到一个新的水平。

In this project funded by the Chemical Theory, Models and Computational Methods program in the Division of Chemistry, Professor Krzysztof Szalewicz of the University of Delaware is developing theoretical and computational methods to model and understand intermolecular forces. When two molecules are placed next to each other, each molecule acts on its partner with a weak force that is an order of magnitude weaker than the chemical forces that bind atoms together into molecules. A broad range of physical, chemical, and biological phenomena originate from such intermolecular forces. Knowledge of intermolecular forces is necessary to interpret a variety of phenomena including the structure and function of crystals and proteins. Professor Szalewicz and his coworkers are developing new ideas to improve the modeling of intermolecular forces and to extend their range of applicability. This research is expected to have an impact on metrology standards, energy resource exploration, atmospheric modeling, understanding processes in interstellar clouds, simulating biological phenomena, and predicting the crystalline forms of drugs. These computational approaches are being implemented in software that is freely available to the research community. To predict properties of clusters, biomolecular aggregates, and condensed phases, one needs to know the potential energy surfaces, also called force fields, of the system that describe the possible mutual orientations and separations between molecules. Such surfaces can be computed via ab initio approaches using symmetry-adapted perturbation theory (SAPT). SAPT provides a unique ability to interpret properties dependent on intermolecular forces in terms of the four fundamental physical mechanisms that lead to the electrostatic, exchange, induction, and dispersion contributions to the interaction energies. SAPT is based on monomers described by density-functional theory (DFT), a method denoted as SAPT (DFT), and is as accurate as the regular SAPT but significantly faster. Professor Szalewicz is working to develop SAPT further and increase its range of applicability. and strives to expand SAPT's range of applicability to molecules with hundreds of atoms, a step in the direction of physics-based biomolecular force fields which may bring biomolecular simulations to a new level of reliability.