Restricted open-shell Kohn–Sham theory for π–π transitions. II. Simulation of photochemical reactions

We present first principles molecular dynamics simulations of the photochemistry of butadiene and cyclohexadiene. The excited state is described with restricted open-shell Kohn–Sham theory. We observe cis–trans isomerizations for 1,3-butadiene and conrotatory ring opening of cyclohexadiene. The excitation of a sample of several butadiene molecules leads to the formation of an excimer.