Intermolecular Forces from Interacting Densities

来自奥克兰大学的Maria Szczesniak-Bryant和Grzegorz Chalasinki得到了化学系化学理论、模型和计算方法计划的支持，以开发理论和计算方法来研究弱的、非共价相互作用。这种闭壳原子和分子之间的相互作用支配着一系列广泛的化学和物理现象，从蛋白质的结构和自组装到材料的性质和“稀疏物质”。计算化学越来越多地转向密度泛函理论(DFT)来现实地描述这些力。虽然DFT本身不能实现这一目标，但基于DFT的对称性适应微扰理论在实现这一描述方面取得了重大进展。然而，微扰理论也有其局限性，尤其是在收敛方面。研究人员正在开发一种基于密度泛函理论的替代方法，该方法不基于微扰理论，可以提供同样准确的、潜在准确的相互作用能量。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成分，如静电、交换、诱导和色散。该项目中开发的形式化方法可以扩展到大量的交互子系统。私人投资促进机构打算将这一方法进一步推广到开壳案件。该方法源于DFT中超分子相互作用能的精确定义，因此，它还可以指导为处理分子间作用力而设计的新的交换关联泛函的构建。该项目为奥克兰大学的学生，特别是本科生提供了一个从事与开发和测试新的计算方法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(一流研究机构)的研究人员和学生之间的合作。拟议中的计划将培训研究生方法开发和计算机编程--这是当今知识经济中非常需要的技能。作为该项目的结果而开发的计算机代码将是开放源码的，并可免费向广大研究人员提供。

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.