Symmetry Projected Coupled Cluster Theory

William Marsh Rice大学的Gustavo Scuseria获得了化学学部化学理论、模型和计算方法项目的奖励，为具有挑战性的分子开发了准确且负担得起的计算方法。我们感兴趣的系统有几个电子，它们以相互影响的方式导致许多具有相似能量的状态。这种类型的系统被称为“强相关”，并且可以表现出新的特性，这些特性有可能刺激许多领域的技术进步。然而，这些系统在理论上是具有挑战性的，并且对于当前的计算方法来说往往是难以处理的。Scuseria教授的团队正在开发一种精确的新方法，可以应用于大型、现实的系统，同时在强相关系统中提供优越的结果。研究人员正在努力继续开发新方法，并将该方法应用于过渡金属簇和多环芳烃等重要系统，以便为技术相关系统提供有用的见解。Scuseria博士参与了休斯顿地区的外展活动。具体来说，他正在与莱斯大学的拉丁美洲研究生协会组织活动。他就学术界和工业界的就业机会提供非正式的建议。Scuseria博士还参与了Rice Science Cafe，在那里与公众讨论有关科学和技术的想法。强相关性无处不在，在技术上也很重要，但不幸的是，除了少数计算方法之外，无法准确描述强相关性。一种比较有前途的处理强相关的方法是使用对称投影，即恢复一个破对称波函数的对称保持分量。对称投影是一个黑盒子，对称投影平均场方法可以应用于具有几十个甚至几百个强相关电子的系统。为了达到强相关系统的定量精度，Scuseria小组正致力于将对称投影平均场方法扩展到对称投影耦合聚类理论。该理论结合了对称投影对强相关描述的优点和耦合簇理论对弱相关描述的优点，成为黑盒多参考耦合簇理论的一种形式。这种新方法有可能在同等基础上有效可靠地处理弱相关性和强相关性，同时提供属性和其他期望值的直接计算。Scuseria小组继续发展和扩展对称投射耦合团簇理论，他们目前的应用是显示自旋受挫和伴随磁序的强相关系统，这应该为未来的技术发展提供有价值的见解。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。

Gustavo Scuseria of William Marsh Rice University is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry Division to develop accurate and affordable computational methods for challenging molecules. The systems of interest have several electrons that influence each other in ways that lead to many states with similar energies. Systems of this type are called "strongly-correlated" and can exhibit novel properties which have the potential to spur technological advancement in a number of fields. However, these systems are challenging to theoretically describe and are often intractable for current computational methods. Professor Scuseria's group is developing a new approach that is accurate and can be applied to large, realistic systems, all the while giving superior results for strongly correlated systems. The researchers are working both to continue to develop the new approach and to apply the method to important systems like transition-metal clusters and polycyclic aromatic hydrocarbons in order to provide useful insights into technologically-relevant systems. Dr. Scuseria is involved in outreach activities in the Houston area. Specifically he is organizing events with the Latin American Graduate Student Association at Rice University. He provides informal advice about job opportunities in academia as well as in industry. Dr. Scuseria is also involved in the Rice Science Cafe, where ideas about science and technology are discussed with the general public. Strong correlations are ubiquitous and technologically important, but unfortunately cannot be accurately described except by a handful of computational approaches. One of the more promising approaches for the treatment of strong correlation is the use of symmetry projection, i.e. recovering the symmetry-preserving component of a broken-symmetry wavefunction. Symmetry projection is black box, and symmetry projected mean-field methods can be applied to systems with dozens or even hundreds of strongly correlated electrons. In order to reach quantitative accuracy for strongly-correlated systems, the Scuseria group is working to extend their symmetry projected mean-field methods to symmetry projected coupled cluster theory. This theory combines the advantages of symmetry projection for the description of strong correlation on the one hand with coupled cluster theory for the description of weak correlation on the other, becoming a form of black-box multireference coupled cluster theory. The new approach has the potential to efficiently and reliably treat weak and strong correlations on equal footing while affording the straightforward computation of properties and other expectation values. While the Scuseria group continues to develop and extend symmetry projected coupled cluster theory, their current applications of the approach are strongly correlated systems which display spin frustration and accompanying magnetic order, which should provide valuable insights for future technological development.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.