Density Functional Theory of Molecular Fragments: Strong Electron Correlation Beyond Density Functional Approximations

在化学系化学理论、模型和计算方法项目的支持下，普渡大学的Adam Wasserman教授正在开发先进的理论和方法，用于分子和材料的电子结构的计算机模拟，具有新的能力，可以高度准确地预测这些系统的性质和解释实验。此外，分子片段密度泛函理论的新方法旨在为日益复杂的系统提供计算效率。沃瑟曼博士和他的研究小组将专注于提高这些方法的准确性和效率，以应对具有挑战性的“强相关类型”系统。在这些系统中，电子相关效应占主导地位，通常无法基于Kohn-Sham密度泛函理论（最广泛使用的电子结构方法）进行标准近似。除了拟议的研究工作所产生的更广泛的影响外，PI在普渡大学拉丁美洲学生社区中的领导作用将继续下去。其他教育活动包括由私人学院协办的两年一次的“随时离散傅里叶变换”学校及工作坊，以及私人学院将继续举办的“科学与社会进步”海外研修班。根据该奖项，Wasserman研究小组将专注于两个主要推力：(1)提高密度泛函理论（DFT）计算的准确性，这些系统超出了最先进的密度泛函近似的范围；(2)提高此类计算的效率。这种分离是由于最近的密度势反演技术的发展而成为可能的，该技术允许计算数值精确的非加性非相互作用动能。为了实现第一个目标，Wasserman和他的团队将采用碎片密度的重叠泛函来构建和测试碎片间交换相关能量泛函的物理动机近似。为了实现第二个目标，将采用双管齐下的方法，其中(a)将根据非加性动能泛函的精确约束开发半局部碎片密度泛函；(b)将使用训练好的神经网络将非局部效应纳入完整的非相互作用动能泛函的元广义梯度近似（GGA）泛函中。所有的进展都将通过密度嵌入计算的开源代码提供给更广泛的科学界。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。

With support from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry, Professor Adam Wasserman of Purdue University is developing advanced theories and methods for computer simulation of the electronic structure of molecules and materials with new capabilities to enable highly accurate prediction of properties and interpretation of experiment for these systems. In addition, the new method of density functional theory of molecular fragments aims to provide computational efficiency for systems of ever-increasing complexity. Dr. Wasserman and his research group will focus on improving both the accuracy and the efficiency of these methods for the challenging systems of the “strongly-correlated type.” These systems in which electron correlation effects dominate, are typically out of reach for standard approximations based on Kohn-Sham Density Functional Theory, the most widely used electronic structure method. In addition to the broader impact resulting from the proposed research efforts, the PI's leadership within the Latin-American community of Purdue students will continue. Other educational activities include a bi-annual School and Workshop on Time-dependent DFT co-organized by the PI and a study-abroad course on “Science and social progress” that the PI will continue organizing.Under this award, the Wasserman research group will focus on two major thrusts: (1) Improving the accuracy of density-functional theory (DFT) calculations for systems that lie beyond the reach of state-of-the-art density-functional approximations; and (2) Improving the efficiency of such calculations. This separation is made possible by the development of recent density-to-potential inversion techniques that allow for the calculation of numerically exact non-additive noninteracting kinetic energies. To achieve the first goal, Wasserman and his group will employ an overlap functional of the fragment densities to construct and test physically motivated approximations for the inter-fragment exchange-correlation energy functional. To achieve the second, a two-pronged approach will be followed in which (a) a semi-local fragment-density functional will be developed based on exact constraints for the non-additive kinetic-energy functional; and (b) a trained neural network will be used to incorporate non-local effects into a meta-generalized gradient approximation (GGA) functional for the full noninteracting kinetic energy functional. All advances will be made available to the broader scientific community through open-source codes for density embedding calculations.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.