Radiation damage on molecular scale commonly occurs due to exposure to UV light or ionizing radiation as applied e.g. for food preservation, waste water treatment, medical treatments, or originating from the sun. Initially, radiation creates highly reactive electronic defects such as electron holes and excess electrons.
These defects can attack organic molecules directly or are converted to intermediate free radicals that react rapidly with most molecules and are responsible for e.g. DNA damage. Free radical scavengers provide protection by capturing these highly reactive species. We propose to study the chemistry of electronic defects in aqueous solution such as formed by irradiation using parameter free, atomistic and electronic modelling based on density functional theory.
The insight gained from this modelling should complement the vast body of experimental research. A computational approach may in particular help rationalizing the transient electronic states playing a role during the early steps of radiation damage, which are less accessible to experiment. We will study the formation of solvated electrons, hydroxyl radicals and other small radicals in water, and investigate the process in presence of free radical scavengers.
The ultimate aim is the simulation of radiation damage to DNA in aqueous solution. Given the extended nature of the electronic defects and high transient mobilities following photoionization or radiolysis, the simulated systems will have to be large, requiring highly accurate and fast electronic structure calculations for up to several thousand atoms.
Moreover, the strong coupling to molecular motion in finite temperature liquid solutions leading to relaxation and solvation can only be treated by molecular dynamics techniques, and requires simulation over periods of time in the order of picoseconds. In order to achieve this, we will validate and expand the capabilities of the density functional program CP2K/QUICKSTEP.
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