Generalized coupled cluster theory for ground and excited state intersections

F Rossi, EF Kjønstad, S Angelico… - The Journal of Physical …, 2024 - ACS Publications
Coupled cluster theory in the standard formulation is unable to correctly describe conical
intersections among states of the same symmetry. This limitation has restricted the practical …

Photoinduced hydrogen dissociation in thymine predicted by coupled cluster theory

EF Kjønstad, OJ Fajen, AC Paul, S Angelico… - Nature …, 2024 - nature.com
The fate of thymine upon excitation by ultraviolet radiation has been the subject of intense
debate. Today, it is widely believed that its ultrafast excited state gas phase decay stems …

Coupled cluster theory for nonadiabatic dynamics: nuclear gradients and nonadiabatic couplings in similarity constrained coupled cluster theory

EF Kjønstad, S Angelico, H Koch - Journal of Chemical Theory …, 2024 - ACS Publications
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 …

[HTML][HTML] A MASH simulation of the photoexcited dynamics of cyclobutanone

JE Lawrence, IM Ansari, JR Mannouch… - The Journal of …, 2024 - pubs.aip.org
In response to a community prediction challenge, we simulate the nonadiabatic dynamics of
cyclobutanone using the map** approach to surface hop** (MASH). We consider the …

Prediction of photodynamics of 200 nm excited cyclobutanone with linear response electronic structure and ab initio multiple spawning

D Hait, D Lahana, OJ Fajen, ASP Paz… - The Journal of …, 2024 - pubs.aip.org
Simulations of photochemical reaction dynamics have been a challenge to the theoretical
chemistry community for some time. In an effort to determine the predictive character of …

Analytic Non-adiabatic Couplings for Selected Configuration Interaction via Approximate Degenerate Coupled Perturbed Hartree–Fock

JP Coe - Journal of Chemical Theory and Computation, 2023 - ACS Publications
We use degenerate perturbation theory and assume that for degenerate pairs of orbitals, the
coupled perturbed Hartree–Fock coefficients are symmetric in the degenerate basis to show …

Analytic Evaluation of Nonadiabatic Couplings within the Complex Absorbing Potential Equation-of-Motion Coupled-Cluster Method

K Chatterjee, Z Koczor-Benda, X Feng… - Journal of Chemical …, 2023 - ACS Publications
We present the theory for the evaluation of nonadiabatic couplings (NACs) involving
resonance states within the complex absorbing potential equation-of-motion coupled-cluster …

Understanding failures in electronic structure methods arising from the geometric phase effect

EF Kjønstad, H Koch - arxiv preprint arxiv:2411.08209, 2024 - arxiv.org
We show that intermediate normalization of the electronic wave function, where a constant
component is enforced, will lead to an asymptotic discontinuity at one point along any path …

Dissecting the ingredients of optimally tuned range-separated hybrid models for reliable description of non-adiabatic couplings

T Izadkhast, M Alipour - The Journal of Chemical Physics, 2023 - pubs.aip.org
Perusing the non-radiative processes requires a reliable prediction of non-adiabatic
couplings (NACs) describing the interaction of two Born–Oppenheimer surfaces. In this …