Abstract
We report an implementation of the linear vibronic coupling (LVC) model within the surface hopping dynamics approach and present utilities for parameterizing this model in a blackbox fashion. This results in an extremely efficient method to obtain qualitative and even semi-quantitative information about the photodynamical behavior of a molecule, and provides a new route toward benchmarking the results of surface hopping computations. The merits and applicability of the method are demonstrated in a number of applications. First, the method is applied to the SO2 molecule showing that it is possible to compute its absorption spectrum beyond the Condon approximation, and that all the main features and timescales of previous on-the-fly dynamics simulations of intersystem crossing are reproduced while reducing the computational effort by three orders of magnitude. The dynamics results are benchmarked against exact wavepacket propagations on the same LVC potentials and against a variation of the electronic structure level. Four additional test cases are presented to exemplify the broader applicability of the model. The photodynamics of the isomeric adenine and 2-aminopurine molecules are studied and it is shown that the LVC model correctly predicts ultrafast decay in the former and an extended excited-state lifetime in the latter. Futhermore, the method correctly predicts ultrafast intersystem crossing in the modified nucleobase 2-thiocytosine and its absence in 5-azacytosine while it fails to describe the ultrafast internal conversion to the ground state in the latter.
Highlights
Different strategies have been developed for reducing the number of electronic structure computations in trajectory dynamics simulations
None of these approaches is in routine use, which probably derives from the fact that they do require a significant amount of electronic structure computations and expert knowledge to be applied successfully
Despite the huge popularity of surface hopping and vibronic coupling (VC) models individually, it is difficult to find any combined application of both methods in the literature,[38] and certainly no generally applicable implementation is available. Such a combination will be highly desirable as it allows speeding up surface hopping simulations by orders of magnitude when compared to on-the-fly dynamics and allows for including essentially an unlimited number of degrees of freedom as opposed to quantum dynamics
Summary
Different strategies have been developed for reducing the number of electronic structure computations in trajectory dynamics simulations. Paper last 30 years, the vibronic coupling (VC) model.[25] VC models provide a description of the main physics of interacting potential surfaces, including the conical shape of their intersections, using only a minimum number of parameters with clear physical meaning They can be parameterized using standardized protocols[25,26,27,28,29] and are commonly used in the context of quantum dynamics, in particular within the wellestablished multiconfigurational time-dependent Hartree (MCTDH) method,[30] and have been shown to be powerful for describing ultrafast nonadiabatic processes in organic and inorganic molecules,[31,32,33,34] in transition metal complexes[27,35,36] and at interfaces.[37] Despite the huge popularity of surface hopping and VC models individually, it is difficult to find any combined application of both methods in the literature,[38] and certainly no generally applicable implementation is available. We deem a general implementation of LVC surface hopping highly desirable
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