A posteriori localization of many‐body excited states through simultaneous diagonalization. Issue 2 (10th October 2022)

• Record Type: Journal Article
• Authors: Blanc, Ambre; Monari, Antonio; Tremblay, Jean Christophe
• Is Part Of: Journal of computational chemistry. Volume 44:Issue 2(2023)
• Page Start: 105
• Page End: 116
• Publication Date: 2022-10-10
• Subjects: excited states -- localization -- particle‐hole pairs; Chemistry -- Data processing -- Periodicals; 542.85
• DOI: 10.1002/jcc.27019
• Languages: English
• ISSNs: 0192-8651

Abstract

Abstract: In this paper we propose a numerical method to localize many‐electron excited states. To characterize the electronic structure of the electronic excited states of a system, quantum chemistry methods typically yield a delocalized description of the excitations. Some a priori localization methods have been developed to provide an intuitive local picture of the excited states. They typically require a good strategy to separate the system of interest from its environment, or a set of a priori localized orbitals, that may reduce their computational accuracy. Here, we introduce an a posteriori method to localize delocalized many‐body excited states directly obtained from quantum chemistry calculations. A localization metric for the excited states is defined from their representation as electron–hole pairs, which is encoded in the transition density matrix. This novel a posteriori strategy thus allows to localize excitons within a volume around selected fragments of a complex molecular system without tempering with its quantum chemical treatment. The method is tested on π ‐stacked oligomers of phenanthrenes and pyrenes. It is found to efficiently localize and separate the excitons according to their character while preserving the information about delocalized many‐body states at a low computational cost. Abstract : A novel method allows to localize many‐body excited states from their representation as electron–hole pairs. The method uses simultaneous diagonalization to efficiently transform, localize, and separate excitons at low computational cost.