Quantum molecular dynamics simulations of the effect of secondary modes on the photoisomerization of a retinal chromophore model

Abstract

In this paper, we report on the performance of various quantum molecu- lar dynamics simulation methods in describing the photo-induced nonadi- abatic dynamics underlying the isomerization process of the retinal chromophore in rhodopsin. We focus on purely quantum vibronic wavepacket techniques and on various trajectory-based schemes, discussing their capability of accurately capture the isomerization process using a two-dimensional two-state model system coupled to an environment of secondary harmonic modes. Numerical results of various algorithms and time-independent grid schemes for the purely quantum approaches are presented, which also serve as benchmark for the trajectory-based calculations. Independent-trajectory and coupled-trajectory methods are compared as well, devoting particular attention to the scaling of their computational cost when increasing the number of degrees of freedom.

Different flavors of exact-factorization-based mixed quantum-classical methods for multistate dynamics

“…MCTDH used as a reference in Section 3, or ab initio multiple spawning used as a reference in ref. 46, EF-based MQC methods offer a generally significantly lower computational cost, 76 while generally being less accurate. An advantage compared to MCTDH however, aside from scaling linearly instead of exponentially with the number of degrees of freedom, is that, like other trajectory-based methods, EF-based MQC methods can be run with arbitrary potentials, including analytical, semi-empirical, ab initio potential energy surfaces computed on-the-fly or even hybrid QM/MM potentials, while MCTDH is only well-suited for systems where the wavefunction is expressed as a sum of products of single-particle wavefunctions, so the potentials should be compatible with this formalism.…”