Atomistic simulations of the formation and destruction of nanoindentation contacts in tungsten

Atomistic simulations of contact formation, indentation, subsequent pulling, and contact failure between a tungsten tip and a tungsten substrate are presented. Different combinations of [111] and [110] crystal directions parallel to the direction of indentation are investigated. The simulations are performed using a Finnis-Sinclair potential for tungsten and a displacement controlled, quasistatic simulation scheme. The simulation setup and the tip geometry are inspired by low temp. scanning tunneling microscope indentation-retraction expts. In the case of identical cryst. orientation of tip and substrate, deformation during indentation and the early stages of retraction is carried exclusively by prismatic dislocation loops. When the so formed nanocontact between the tip and substrate gets smaller, the deformation mechanism changes to at. rearrangements within the neck. For configurations with different crystallog. orientation of the tip and substrate, the deformation is mainly carried by local at. rearrangements within the interface region. Failure of the contact always occurs at the interface. In all cases debris is leftover on the substrate. The simulation results are discussed in the framework of nanoindentation and contact failure. The importance of the atomistic structure of interfaces in nanoscale contact problems is highlighted. [on SciFinder (R)]