Molecular dynamics in low-spin excited states

A Kohn–Sham-like formalism is introduced for the treatment of excited singlet states. Motivated by ideas of Ziegler’s sum method and of restricted open-shell Hartree–Fock theory, a self-consistent scheme is developed that allows the efficient and accurate calculation of excited state geometries. Vertical as well as adiabatic excitation energies for the ${\mathrm{n\to \pi }}^{*}$ transitions of several small molecules are obtained with reasonable accuracy. As is demonstrated for the cis-trans isomerization of formaldimine, our scheme is suited to perform molecular dynamics in the excited singlet state. This represents a first step towards the simulation of photochemical reactions of large systems.