Reduced Scaling Many-Body Electronic Structure Methods: Improved Accuracy and Precision

弗吉尼亚理工学院和州立大学的Edward Valeev获得了化学系化学理论、模型和计算方法项目的奖励，以开发有效和准确的方法来研究大分子、晶体固体和界面的电子性质。通过应用量子力学定律来描述原子、分子和固体中电子的行为，就有可能预测我们周围物质的性质。不幸的是，精确的计算和理论建模的电子行为的系统中有几个原子是超出了能力，即使是目前最强大的超级计算机，由于急剧增加的计算成本与电子的数量。Valeev和他的同事正在开发一种方法，可以将精确计算的计算成本降低许多数量级，并使具有数千个原子的系统的预测模拟成为可能。这些进步对于我们设计具有特定功能的分子和材料的能力至关重要，例如创造将太阳光转化为燃料的新催化剂。 所开发的方法正被纳入广泛使用的软件包，这些软件包可提高国家和国际研究人员的研究能力。（如图解微扰理论和耦合团簇）与相对于系统大小的缩减标度（通过利用算子和状态的低秩和稀疏结构）和精度（通过经由显式相关建立正确的分析结构）。这一发展建立在Valeev及其同事最近的进展基础上，这些进展表明，具有单重、双重和微扰三重的完整基组耦合簇计算可以在具有一千多个原子的闭壳层分子上进行。该项目扩展了处理具有开壳层电子态的分子、电子态的流形以及晶体固体的电子态的方法。秩压缩的效率正在通过将表示定制为特定的电子结构模型来提高。最后，该项目将这些想法应用于高阶耦合团簇模型，以将其适用性扩展到30-50个原子的系统。 除了通过广泛使用的软件包提供这些代码外，正在进行的工作还为研究生和博士后研究员提供了出色的培训。该奖项反映了NSF的法定使命，并被认为值得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来支持。

Edward Valeev of Virginia Polytechnic Institute and State University is supported by an award from the Chemical Theory, Models and Computational Methods Program in the Chemistry Division to develop efficient and accurate methods for studying the electronic properties of large molecules, crystalline solids, and interfaces. It is possible to predict the properties of matter around us by applying the laws of quantum mechanics to describe the behavior of electrons in atoms, molecules, and solids. Unfortunately, exact computational and theoretical modeling of electron behavior in systems with more than a few atoms is beyond the ability of even the most powerful supercomputers currently available due to the steep increase of computational cost with the number of electrons. Valeev and co-workers are developing methods that reduce the computational cost of accurate calculations by many orders of magnitude and make predictive simulations possible for systems with thousands of atoms. Such advances are crucial for our ability to design molecules and materials for particular functions, such as creating new catalysts for converting solar light into fuel. The methods developed are being included in widely-used software packages that may enhance research capabilities for national and international researchers.This project focuses on the development of many-body electronic structure methods (such as the diagrammatic perturbation theory and coupled-cluster) with reduced scaling with respect to system size (by exploiting low-rank and sparse structure of the operators and states) and precision (by building in the correct analytic structure via explicit correlation). This development builds upon recent advances by Valeev and co-workers that demonstrated that complete basis set coupled-cluster with singles, doubles, and perturbative triples calculations could be performed on closed-shell molecules with more than a thousand atoms. This project extends the approach to the treatment of molecules with open-shell electronic states, to manifolds of electronic states, and to electronic states of crystalline solids. The efficiency of the rank compression is being improved by tailoring representations to the particular electronic structure model. Lastly, the project applies these ideas to the high-order coupled-cluster models to extend their applicability to systems with 30-50 atoms. In addition to making these codes available through a widely-used software package, the work being done provides excellent training for graduate students and postdoctoral fellows.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.