Photo-initiated charge-transfer processes play a central role in biophysical systems such as human vision and photosynthesis. While researchers have successfully mimicked these processes for simple isolated systems, our understanding of photo-initiated mechanisms in realistic and complex environments is still in its infancy. In particular, recent experiments have shown that simple descriptions of solvent interactions (either via classical force fields or effective solvent models) are unable to accurately capture the electron dynamics in these environments. These ongoing observations open an entirely new computational area of research in the properties of light-activated processes in explicit solvent, with the opportunity to deeply understand the real-time electron dynamics in large complex systems.<br/><br/>To this end, we have developed a new real-time time-dependent density functional tight binding (RT-TDDFTB) code that efficiently runs on massively-parallelized GPUs. This GPU-enhanced capability allows efficient calculations of real-time electron dynamics of donor-acceptor complexes in the presence of explicit solvent molecules - <i>all treated at the quantum mechanical level</i>. Furthermore, and most importantly, the use of GPUs allows us to calculate the electron dynamics of large solvated systems (~10,000 atoms), whereas conventional approaches are computationally limited to only hundreds of atoms. Using a custom-built GPU cluster with a GTX Titan processor in our laboratory, we are able to understand and rationalize electron-hole recombination effects as a function of solvent polarity, configuration, and energy transfer. Furthermore, this new computational capability gives us mechanistic insight into the electron dynamics of complex environments with the goal of probing charge-transfer dynamics in large systems.

GPU-enabled real-time electron dynamics of large light-harvesting systems in explicit solvent

249th National Meeting (2015)

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