title: Molecular dynamics of single-particle impacts predicts phase diagrams for large scale pattern formation.
abstract: Energetic particle irradiation can cause surface ultra-smoothening, self-organized nanoscale pattern formation or degradation of the structural integrity of nuclear reactor components. A fundamental understanding of the mechanisms governing the selection among these outcomes has been elusive. Here we predict the mechanism governing the transition from pattern formation to flatness using only parameter-free molecular dynamics simulations of single-ion impacts as input into a multiscale analysis, obtaining good agreement with experiment. Our results overturn the paradigm attributing these phenomena to the removal of target atoms via sputter erosion: the mechanism dominating both stability and instability is the impact-induced redistribution of target atoms that are not sputtered away, with erosive effects being essentially irrelevant. We discuss the potential implications for the formation of a mysterious nanoscale topography, leading to surface degradation, of tungsten plasma-facing fusion reactor walls. Consideration of impact-induced redistribution processes may lead to a new design criterion for stability under irradiation.
authors.affiliation: Department of Mathematics, Southern Methodist University, Dallas, Texas 75205, USA. snorris@smu.edu
authors.forename: Scott A
authors.initials: SA
authors.lastname: Norris
authors.forename: Juha
authors.initials: J
authors.lastname: Samela
authors.forename: Laura
authors.initials: L
authors.lastname: Bukonte
authors.forename: Marie
authors.initials: M
authors.lastname: Backman
authors.forename: Flyura
authors.initials: F
authors.lastname: Djurabekova
authors.forename: Kai
authors.initials: K
authors.lastname: Nordlund
authors.forename: Charbel S
authors.initials: CS
authors.lastname: Madi
authors.forename: Michael P
authors.initials: MP
authors.lastname: Brenner
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Aziz
mesh_terms: D004735:Energy Transfer; D007477:Ions / Q000737:chemistry*; D008956:Models, Chemical; D056004:Molecular Dynamics Simulation; D049329:Nanostructures; D009688:Nuclear Reactors / Q000295:instrumentation*; D011839:Radiation, Ionizing; D013499:Surface Properties
chemical_list: D007477:Ions