Strong Influence of Decoherence Corrections and Momentum Rescaling in Surface Hopping Dynamics of Transition Metal Complexes

Abstract

The reliability of different parameters in the surface hopping method is assessed for a vibronic coupling model of a challenging transition metal complex, where a large number of electronic states of different multiplicities are met within a small energy range. In particular, the effect of two decoherence correction schemes and of various strategies for momentum rescaling and treating frustrating hops during the dynamics is investigated and compared against an accurate quantum dynamics simulation. The results show that surface hopping is generally able to reproduce the reference but also that small differences in the protocol used can strongly affect the results. We find a clear preference for momentum rescaling along only one degree of freedom, using either the nonadiabatic coupling or the gradient difference vector, and trace this effect back to an enhanced number of frustrated hops. Furthermore, reflection of the momentum after frustrated hops is shown to work better than to ignore the process completely. The study also highlights the importance of the decoherence correction but neither of the two methods employed, en-ergy based decoherence or augmented fewest switches surface hopping, performs completely satisfactory and we trace this effect back to a lack of size-consistency. Finally, the effect of different methods for analysing the populations is highlighted. More generally, the study emphasises the importance of the often neglected parameters in surface hopping and shows that there is still need for simple, robust, and generally applicable correction schemes.

Competing ultrafast photoinduced electron transfer and intersystem crossing of [Re(CO)$$_3$$(Dmp)(His124)(Trp122)]$$^+$$ in Pseudomonas aeruginosa azurin: a nonadiabatic dynamics study

“…First, all nonadiabatic dynamics simulations published so far [17][18][19][20]22] and the present results strongly indicate that the lifetime of a pure 1 MLCT is on the order of only 10 fs, after which a spin-mixed 1,3 MLCT wave function is formed due to the large SOCs. Hence, it is very unlikely that the 1 MLCT → 1 CS pathway is of high relevance.…”

“…Furthermore, the curvature of the excited-state potentials is likely to be different from the one of the ground-state potential. However, it is unclear how severe the latter approximation is, as LVC models worked well for the [Re(CO) 3 (Phen)(Im)] + complex without Trp [17][18][19][20].…”

“…The ultrafast dynamics of the small system (shown in Fig. 1c) was studied in detail with quantum chemistry [14][15][16], quantum dynamics [17][18][19], model-potentialbased surface hopping [20], or QM/MM-based surface hopping [16,[21][22][23]. These studies have firmly established the importance of the environment effects on the In contrast to the small system, the photocycle of the medium and large systems-both of which include the Trp amino acid-has been investigated to a much smaller extent.…”

Unconventional two-step spin relaxation dynamics of [Re(CO)3(im)(phen)]+ in aqueous solution

“…The fact that both simulations nd this ultrafast initial decay is encouraging, showing that very distinct treatments of nuclear motion (quantum-mechanical vs. surface hopping, see also ref. 48) do not affect this purely electronic ISC process. However, for later times it is not possible to clearly identify a decay of the singlet population in ref.…”

Excited-state dynamics of molecules with classically driven trajectories and Gaussians

“…It is interesting to note, however, that only a few works have been highlighting the role of such decoherence correction for the nonadiabatic dynamics of molecules (see, e.g. [171,[183][184][185][186]). In the following, we introduce some preliminary calculations aiming at assessing the role of a decoherence correction (EDC) in TSH for the molecule DMABN, and comparing the outcome of TSH dynamics with the one of AIMS.…”