Interaction of energetic particles with ice surfaces: molecular dynamics simulation using the REAX potential

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The interaction of energetic particle radiation with ice surfaces is of interest in particular for investigations in the space sciences. In our solar system the surfaces of moons and comets are subject to particle irradiation. Furthermore, the interaction of cosmic radiation with small ice clusters (dust particles) is relevant. Recent space missions - such as the ROSETTA mission to comet Churyumov-Gerasimenko - directed attention to the physics and chemistry of ice surfaces. In addition, such studies are relevant for the analytical technique of mass spectrometry, where either icy biological samples are studied by SIMS (secondary ion mass spectrometry) or reactive species are enclosed in an inert ice matrix (matrix isolation spectroscopy). The objective of this project is to use molecular dynamics simulation for enhancing our understanding of the interaction of energetic particles with ice surfaces. Such processes are relevant for the space sciences; they include the interaction of the solar wind, of magnetospheric ions and of cosmic radiation with the icy surfaces of planets and moons, comets and ice-covered dust particles. Modern REAX potentials allow to model both the repulsive interaction governing energetic collisions and the bonds in molecular solids, such as in the ice mixtures that will be used in this project. Thus the simulation of bond dissociations and formations occurring during and after impact, and hence also the formation of new molecules by reactions, become feasible. In this project we aim at obtaining novel theoretical information on the modification and sputter erosion of ice surfaces by particle irradiation. Typical scenarios to be studied include the interaction with ions contained in the solar wind, in the magnetosphere of Jupiter and in the cosmic radiation.