title: Surface hopping trajectory simulations with spin-orbit and dynamical couplings.
abstract: In this paper we consider the inclusion of the spin-orbit interaction in surface hopping molecular dynamics simulations to take into account spin forbidden transitions. Two alternative approaches are examined. The spin-diabatic one makes use of eigenstates of the spin-free electronic Hamiltonian and of Ŝ(2) and is commonly applied when the spin-orbit coupling is weak. We point out some inconsistencies of this approach, especially important when more than two spin multiplets are coupled. The spin-adiabatic approach is based on the eigenstates of the total electronic Hamiltonian including the spin-orbit coupling. Advantages and drawbacks of both strategies are discussed and illustrated with the help of two model systems.
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Risorgimento 35, 56126 Pisa, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Granucci
authors.forename: Maurizio
authors.initials: M
authors.lastname: Persico
authors.forename: Gloria
authors.initials: G
authors.lastname: Spighi