Reduced-Scaling Coupled Cluster Theory in the Frequency and Time Domains

在化学系化学理论、模型和计算方法计划的支持下，弗吉尼亚理工学院和州立大学的Daniel Crawford教授将开发能够对分子，特别是手性分子进行计算表征的方法和途径。手性分子表现出利手；因此，分子有左旋和右旋两种形式，这些形式使平面偏振光波朝着相反的方向旋转。了解手性分子对制药工业特别重要，因为一种手性形式可能具有很大的药用价值，而另一种形式可能没有价值甚至有毒。准确预测手性分子的光学性质是计算化学的一项艰巨任务。虽然简单分子性质的计算机模型已经很好地建立了，但手性分子与光的相互作用即使对于最先进的计算方法也是独特的挑战。在这项研究项目中，克劳福德教授和他的同事们正在努力开发健壮而准确的计算技术，这些技术比目前的方法耗时更少。这些计算工具有可能帮助研究人员更好地理解手性分子结构之间的关系以及它们与光的相互作用。此外，这项研究计划将为研究生和本科生提供基本理论和量子化学方法发展方面的教育和培训。在这个项目中开发的软件将包括在PSI4中，这是一个广泛使用的计算化学包，社区可以免费获得。克劳福德博士是PSI4的主要开发者之一。在这个奖项下，丹尼尔·克劳福德教授和弗吉尼亚理工大学的同事们将通过互补的方法简化耦合簇理论，努力推进手部特征的高精度建模。Crawford小组将扩展他们最近的合作工作，开发一种“图解”随机耦合簇方法，该方法将高精度耦合簇方法的解决方案的存储成本降低100倍(通过四次激发)，以利用他们新开发的方法来降低基本相关波函数的维度。此外，在他们证明引入依赖时间的外部电场产生的波函数稀疏性远远大于场扰动波函数的稀疏性之后，Crawford团队将开发一种局部相关的实时耦合集群方法，旨在利用现有的线性缩放框架。最后，他们将利用先进的相关波函数开发和实现第一批振动圆二色谱模拟。这些新模型的开发将涉及到与实验者和理论家的密切合作，这是克劳福德实验室研究的一个标志。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 Daniel Crawford of Virginia Polytechnic Institute and State University will develop methods and approaches that enable the computational characterization of molecules, especially chiral molecules. A chiral molecule displays handedness; thus, there are left-handed and right-handed forms of the molecule and these forms rotate plane-polarized light waves in opposite directions. Understanding chiral molecules is especially important to the pharmaceutical industry as one chiral form may be of great medicinal value, while the other form may be of no value or even toxic. The accurate prediction of the optical properties of chiral molecules is a daunting task for computational chemistry. While computer models of simple molecular properties are well established, interactions of chiral molecules with light present unique challenges even for state-of-the-art computational methods. In this research project, Professor Crawford and coworkers are working to develop robust and accurate computational techniques that are less time-intensive than current methods. These computational tools have to potential to help researchers better understand the relationship between chiral molecular structures and their interactions with light. Further, this research program will the provide for the education and training of graduate and undergraduate students in the fundamental theory and development of quantum chemical methods. Software developed during this project will be included in PSI4, a widely used computational chemistry package that is freely available to the community. Dr. Crawford is one of the lead developers of PSI4.Under this award, Professor Daniel Crawford and coworkers at Virginia Tech will endeavor to advance the high-accuracy modeling of chiroptical properties by streamlining coupled cluster theory through complementary approaches. The Crawford group will be extending their recent collaborative work on the development of a "diagrammatic" stochastic coupled cluster approach that exhibits a hundred-fold reduction in the memory costs for the solution of high-accuracy coupled cluster methods (through quadruple excitations) to take advantage of their newly developed methods for reducing the dimensionality of the underlying correlated wave functions. In addition, following their demonstration that the introduction of a time-dependent external electric field yields substantially greater wave function sparsity than that of the field-perturbed wave function, the Crawford team will develop a locally correlated real-time coupled cluster approach that is designed to take advantage of existing linear-scaling frameworks. Finally, they will develop and implement the first simulations of vibrational circular dichroism spectroscopy using advanced correlated wavefunctions. Development of these new models will involve close collaborations with both experimentalists and theorists, a hallmark of studies in the Crawford laboratory.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.