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

高能粒子辐射与冰表面的相互作用对空间科学的研究特别感兴趣。在我们的太阳系中，卫星和彗星的表面受到粒子辐射。此外，宇宙辐射与小冰团(尘埃颗粒)的相互作用也是相关的。最近的太空任务--例如罗塞塔对丘留莫夫-格拉西缅科彗星的任务--将注意力集中在冰面的物理和化学上。此外，这种研究与质谱学分析技术有关，在质谱学技术中，冰冻的生物样品被二次离子质谱仪(SIMS)研究，或者活性物质被包裹在惰性冰基质中(基质隔离光谱学)。这个项目的目的是利用分子动力学模拟来加深我们对高能粒子与冰表面相互作用的理解。这类过程与空间科学有关；其中包括太阳风、磁层离子和宇宙辐射与行星和卫星、彗星和被冰覆盖的尘埃颗粒的冰面的相互作用。现代的reax势允许对支配能量碰撞的排斥相互作用和分子固体中的键进行建模，例如将在该项目中使用的冰混合物中的键。因此，模拟碰撞中和碰撞后发生的键的解离和形成，从而也可以通过反应形成新的分子成为可能。在这个项目中，我们的目标是获得关于粒子辐照对冰表面的改性和溅射侵蚀的新的理论信息。要研究的典型情景包括与太阳风、木星磁层和宇宙辐射中包含的离子的相互作用。

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.