Modelling surface restructuring by slow highly charged ions

We theoretically investigate surface modifications on alkaline earth halides due to highly charged ion impact, focusing on recent experimental evidence for both etch pit and nano-hillock formation on CaF2 [A. El-Said et al, PRL 109, 117602 (2012)]. We discuss mechanisms for converting the projectile potential and kinetic energies into thermal energy capable of changing the surface structure. A proof-of-principle classical molecular dynamics simulation suggests the existence of two thresholds which we associate with etch pit and nano-hillock formation in qualitative agreement with experiment.