2024/03/01 by Eirik F. Kjønstad, Kjønstad, Eirik F., Sara Angelico +3 · 4 citations
Chemistry · Physics and Astronomy · #Advanced NMR Techniques and Applications #Chemical Physics (physics.chem-ph) #FOS: Physical sciences #Nuclear physics research studies #Quantum chaos and dynamical systems
paper · pdf · doi:10.48550/arxiv.2403.01007
openalex publication_date 2024/03/01 · openalex created_date 2024/03/06 · openalex updated_date 2026/07/28
Coupled cluster theory is one of the most accurate electronic structure methods for predicting ground and excited state chemistry. However, the presence of numerical artifacts at electronic degeneracies, such as complex energies, has made it difficult to apply it in nonadiabatic dynamics simulations. While it has already been shown that such numerical artifacts can be fully removed by using similarity constrained coupled cluster (SCC) theory [J. Phys. Chem. Lett. 2017, 8, 19, 4801-4807], simulating dynamics requires efficient implementations of gradients and nonadiabatic couplings. Here, we present an implementation of nuclear gradients and nonadiabatic derivative couplings at the similarity constrained coupled cluster singles and doubles (SCCSD) level of theory, thereby making possible nonadiabatic dynamics simulations using a coupled cluster theory that provides a correct description of conical intersections between excited states. We present a few numerical examples that show good agreement with literature values and discuss some limitations of the method.