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

在化学系化学理论、模型和计算方法计划的支持下，普渡大学的亚当·沃瑟曼教授正在开发先进的理论和方法，用于计算机模拟分子和材料的电子结构，并具有新的能力，以实现对这些系统的性质的高精度预测和实验解释。此外，分子碎片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精确度和效率，以应对具有挑战性的“强关联类型”系统。在这些体系中，电子相关效应占主导地位，通常不能用最广泛使用的电子结构方法Kohn-Sham密度泛函理论进行标准近似。除了拟议的研究工作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地位将继续下去。其他教育活动包括由PI联合举办的关于依赖时间的DFT的两年一次的学校和研讨会，以及PI将继续举办的关于“科学和社会进步”的留学课程。在这个奖项下，沃瑟曼研究小组将专注于两个主要方面：(1)提高处于最先进密度泛函近似范围之外的系统的密度泛函理论(DFT)计算的准确性；以及(2)提高此类计算的效率。这种分离是由于最近密度-势反转技术的发展，这些技术允许计算精确的非加性非相互作用动能。为了实现第一个目标，Wasserman和他的团队将使用碎片密度的重叠泛函来构建和测试碎片间交换关联能量泛函的物理激励近似。为了实现第二种方法，将遵循双管齐下的方法，其中(A)将基于对非可加动能泛函的精确约束来开发半局部碎片密度泛函；(B)将训练好的神经网络用于将非局部效应结合到针对完全非相互作用动能泛函的准广义梯度近似(GGA)泛函中。所有的进展将通过用于密度嵌入计算的开源代码提供给更广泛的科学界。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.