Massively Parallel Real-Time TDDFT Simulations of Electronic Excitations in DNA by Energetic Protons*

In electronic stopping processes, electronic excitations are produced by fast-moving ions. This phenomenon is at the heart of DNA damage via ion irradiation, which is central to ion beam cancer therapy. A molecular-level understanding of this process is necessary to advance medical technology. Unfortunately, experimental studies remain scarce due to their requirement for extensive use of synchrotron facilities. Quantum-mechanical simulations on supercomputers offer an alternative route for investigating this problem. We will discuss results acquired from our highly scalable implementation of real-time time-dependent density functional theory (RT-TDDFT) simulations (1,2) on current generation HPC systems, as well as next-generation many-integrated-core architectures. This cutting-edge application of RT-TDDFT simulations has unveiled details of energy transfer, electronic excitations, and charge fluctuations in DNA under ion irradiation that would be unattainable without petascale simulations.
(1) A. Schleife, E. W. Draeger, Y. Kanai, and A. A. Correa,J. Chem. Phys. 137, 22A546 (2012).
(2) A. Schleife, E. W. Draeger, V. M. Anisimov, A. A. Correa, and Y. Kanai, Comput. Sci. Eng. 16, 54 (2014).