Nonlocal Density Functional Theory of Molecules and Solids

宾夕法尼亚大学的陶建民得到了化学学部化学理论、模型和计算方法项目的支持，开发了密度泛函理论（DFT）的改进方法。在电子材料、器件以及化学和物理过程的计算机辅助设计中，电子性质的准确预测起着决定性的作用。虽然许多基于波函数的方法精度很高，但它们的计算成本过于昂贵，无法用于实际应用。对于大型多原子系统，DFT是唯一一种既能满足精度要求又能满足效率要求的方法，因此它是应用最广泛的电子结构方法。然而，常用的密度泛函无法达到普遍的精度。Tao和同事专注于开发具有更广泛适用性的功能。这些功能被用于研究不同系统的性质，如（水）团簇和发光低聚物和聚合物。这项工作涉及方法开发和数值应用。该项目还包括主要针对本科生的暑期拓展项目。本研究项目的目标是开发和应用非局部密度泛函（DFT），包括一种新的用于远距离范德华相互作用的非局部相关能泛函。这项工作的重点是解决或减轻常用密度泛函遇到的一些长期存在的困难。DFT方法的一个主要突出问题是密度泛函可能对一个或多个系统类别准确，但不是对所有系统准确，或者对一个或多个属性准确，但不是对所有属性准确。该项目的目标是开发具有普遍准确性和更广泛适用性的密度泛函，以便在相同的基础上使用相同的密度泛函解决各种化学和物理问题。这样的密度泛函必须是非局部的，因为库仑相互作用的性质是非局部的。本科生、研究生和博士后都参与了这个项目的各个方面。

Jianmin Tao of the University of Pennsylvania is supported by the Chemical Theory, Models and Computational Methods program in the Chemistry Division to develop improved methods for density functional theory (DFT). In the computer-aided design of electronic materials, devices, as well as chemical and physical processes, accurate prediction of electronic properties plays a decisive role. While many wave function-based methods are highly accurate, their computational costs are too expensive to be generally useful for practical applications. For large many-atom systems, DFT is the only method with both the required accuracy and efficiency and for that reason it is the most widely used electronic structure method. However, commonly-used density functionals are unable to achieve universal accuracy. Tao and coworkers focus on developing functionals with a wider range of applicability. These functionals are being used to study the properties of diverse systems such as (water) clusters and light-emitting oligomers and polymers. The work involves both method development and numerical application. The project also includes summer outreach programs aimed primarily at undergraduates.The goal of this research project is the development and application of nonlocal density functionals (DFT), including a new nonlocal correlation energy functional for long-range van der Waals interactions. The focus of this effort is on solving or mitigating some long-standing difficulties that commonly-used density functionals encounter. A major outstanding problem for DFT methodology is that a density functional may be accurate for one or more classes of systems, but not for all systems, or for one or more properties, but not for all properties. A goal of this project is to develop a density functional with universal accuracy and wider applicability so that diverse chemical and physical problems can be solved on the same footing, with the same density functional. Such a density functional must be nonlocal, because the nature of the Coulomb interaction is nonlocal. Undergraduates, graduate students and postdocs are involved in various aspects of this project.