Molecular Dynamic Simulations of the Collision between Copper Ions, SF6 Molecules and a Polyethylene Surface: A Study of Decomposition Products and an Evaluation of the Self‐Diffusion Coefficients

Abstract

AbstractMolecular dynamics simulations are used to study the interaction between incident copper ions, SF6 molecules and a polyethylene surface. Average particle velocities from 15 to 21 km · s−1 are tested in steps of 2 km · s−1. The damage to the polyethylene crystal is reviewed in terms of material heating, local molecular disorder and bond breaking accompanied by particle emissions. Two types of emitted particles are distinguished to explain the degradation of the polymer. The first corresponds to free radicals with molecular formula CnH2n+1 and the second takes into account all other possible molecules, especially hydrogen atoms and carbonaceous molecules. The formation of CuF molecules during the interaction is shown and this result is discussed on the basis of other theoretical results concerning the calculations of plasma composition. The self‐diffusion coefficients of the emitted atoms are calculated by using two different methods: the alternative Green‐Kubo expression, based on the integrated velocity autocorrelation function, and the Einstein expression, based on the mean‐square displacement autocorrelation function.magnified image