Trajectory surface hopping molecular dynamics simulation by spin-flip time-dependent density functional theory

This paper presents the nonadiabatic molecular dynamics simulation combined with the spin-flip time-dependent density functional theory (SF-TDDFT). In contrast to the conventional single-reference electronic structure methods, which have difficulty in describing the S₀/S₁ conical intersections, the SF-TDDFT can yield the correct topology of crossing points. Thus, one expects that the method can take naturally into account the S₁ → S₀ nonadiabatic transitions. We adopt Tully's fewest switch surface hopping algorithm by introducing the analytic SF-TDDFT nonadiabatic coupling vector. We apply the proposed method to the photoisomerization reactions of E-azomethane, methanimine, and ethene molecules and reproduce the results of previous studies based on the multireference methods. The proposed approach overcomes the ad hoc treatment of S₁ → S₀ transition at the single-reference calculation level and affords both the dynamics on the S₁ state and the recovery of the S₀ state with modest computational costs.