Intermolecular Forces from Interacting Densities

来自奥克兰大学的Maria Szczesniak-Bryant和Grzegorz Chalasinki获得了化学学部化学理论、模型和计算方法项目的奖励，他们开发了研究弱、非共价相互作用的理论和计算方法。这种闭壳原子和分子之间的相互作用控制着从蛋白质结构和自组装到材料和“稀疏物质”性质的广泛的化学和物理现象。计算化学越来越多地转向密度泛函理论（DFT）来真实地描述这些力。虽然单靠DFT无法实现这一目标，但基于DFT的对称自适应摄动理论在这方面取得了重大进展。然而，微扰理论也有其局限性，尤其是在考虑收敛性时。研究人员正在开发一种替代的基于dft的方法，这种方法不以微扰理论为基础，可以提供同样精确的、潜在精确的相互作用能量。在该方法中，相互作用能被定义为单体密度的泛函，它可以准确地包括相互作用能的所有基本组成部分，如静电、交换、感应和色散。在这个项目中开发的形式体系可以扩展到大量的交互子系统。pi打算将这种方法进一步推广到开壳情况。所提出的方法来源于DFT中超分子相互作用能的精确定义，因此，它也可以指导用于处理分子间力的新的交换相关泛函的构建。该项目为奥克兰大学的学生，特别是本科生提供了一个参与与新计算方法的开发和测试相关的基础研究的机会。拟议的活动促进了奥克兰（一所中等规模的地区性大学）和华沙大学（一所主要研究机构）的研究人员和学生之间的合作。该计划将培养研究生在方法开发和计算机编程方面的技能，这些技能在当今的知识经济中非常需要。该项目开发的计算机代码将是开源的，并免费提供给广泛的研究人员社区。

Maria Szczesniak-Bryant and Grzegorz Chalasinki from Oakland University are supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry division to develop theoretical and computational methods to study weak, non-covalent interactions. Such interactions between closed-shell atoms and molecules govern a wide spectrum of chemical and physical phenomena from protein structure and self-assembly to the properties of materials and "sparse matter". Computational chemistry increasingly turns to density functional theory (DFT) for a realistic description of these forces. While DFT alone cannot accomplish this goal, the symmetry adapted perturbation theory based on DFT made major inroads toward such a description. Yet perturbation theory, too, has its limitations especially as concerns convergence. The researchers are developing an alternative DFT-based method which is not grounded in perturbation theory and which can provide equally accurate, potentially exact, interaction energies. In the proposed approach the interaction energy is defined as a functional of monomer densities and it can accurately include all the essential components of interaction energy such as electrostatic, exchange, induction, and dispersion. The formalism developed in this project is expandable to large number of interacting subsystems. The PIs intend to further generalize this approach to the open-shell case. The proposed method is derived from the exact definition of supermolecular interaction energy within DFT and, therefore, it can also guide the construction of new exchange-correlation functionals designed for the treatment of intermolecular forces.This project offers students at Oakland University, particularly undergraduates, an opportunity to engage in basic research related to development and testing of new computational methodologies. The proposed activities promote the collaboration between researchers and students from Oakland, a mid-size regional University, and the University of Warsaw, a prime research institution. The proposed program will train graduate students in method development and computer programming - the skills in much demand in today's knowledge-based economy. The computer codes developed as a result of this project will be open-source and available free of charge to a broad community of researchers.