and obtain energy surfaces at that given constant load. Evidently that means, that the distance between the slabs has to be adjusted accordingly. Employing this process, which was also used in a very similar way by Cahangirov et al. [@cahangirov:12], we construct quantum mechanical energy- and force-maps for the quasi-static sliding system, both with and without relaxation of atoms.

It has to be pointed out that this model is not intended to simulate a macroscopic copper on copper system which would feature multiple grains, oxidation, impurities, and other imperfections. The aim is rather to study a model for dissipative sliding under idealized and controlled conditions. We believe that the modeled system and the computational method are ideally suited for this endeavor for the following reasons: i) commensurate sliding of a Cu(111) tip on Cu(111) was previously found to exhibit wearless atomic stick-slip motion, both in molecular dynamics simulations [@sorensen:96; @martini:09], and experiments in ultra-high vacuum [@bennewitz:99]. This is in contrast to results for Cu(100) on Cu(100) where both plastic deformations and wear play an important role [@sorensen:96; @nieminen:92]. ii) Garvey et al. showed in a recent series of papers on KCl sliding on Fe(100) that the investigation of shearing interfaces 