Mixed Quantum-Classical Study of the Nonadiabatic Dynamics in Photosynthetic Systems

Abstract

Quantum mechanics often participates importantly in the dynamics of biological systems. Understanding such an aspect becomes crucial when investigating nonadiabatic events within biological molecular complexes. Indeed, nonadiabaticity is an essential element in many fundamental processes such as electron and energy transfers. However, due to the immense size of any biological system, purely quantum mechanical descriptions are simply intractable. For this reason, mixed quantum-classical approaches, where an important part of the system is handled quantum mechanically and its remainder is treated through relatively simple classical mechanics, have become widely applied. Poisson bracket mapping equation (PBME), as an example of the mixed quantum-classical approach, is an attractive scheme with its applicability even to very large systems. Here, we show that PBME can be efficiently applied to studying photosynthetic energy transfer processes and to elucidating the detailed role of the surrounding protein. We will also discuss its limitations in comparison with the results of a more rigorous approach. We will also propose a simple scheme to improve the long-time behavior of PBME in terms of correct population distributions. Future prospects will also be discussed.