Dresden 2026 – scientific programme

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O: Fachverband Oberflächenphysik

O 37: Electronic structure theory I

O 37.1: Invited Talk

Tuesday, March 10, 2026, 10:30–11:00, TRE/PHYS

Calculations of excited electronic states by converging on saddle points on the electronic energy surface — •Hannes Jonsson — University of Iceland, Reykjavik, Iceland

Calculations of excited electronic states are important in various contexts, e.g. photocatalysis and molecular motors. They are challenging as commonly used optimization methods are based on minimization and thereby converge on the ground state. A time-dependent formulation of density functional theory (TD-DFT), especially within the linear response and adiabatic approximations, is therefore often used to estimate excited states, but can fail especially when significant charge transfer occurs and when states are close in energy. Alternatively, by converging on a saddle point on the electronic energy surface, the orbitals can be optimised for an excited state to provide a solution of the underlying Kohn-Sham equations with higher energy than the ground state. This turns out to a give more robust estimate of the excitation energy than TD-DFT with computational effort similar to that of a ground state calculation. Several applications of this approach with commonly used density functionals will be presented, as well as calculations using a self-interaction corrected functional giving improved results. In particular, excited states involving twisting of a C=C bond, e.g. in molecular motors, and Rydberg states have been analysed. As a solid state application, the various states involved in the optical preparation of a pure spin state in nitrogen/vacancy defect in diamond will be presented. The results show close agreement with more computationally demanding calculations as well as experiments.

Keywords: excited state; density functional; saddle point; molecular motor; defect state