Multiregional hybrid method and its application: formation of an atomic protrusion at an atomic force microscope tip...

We present a multiregional hybrid scheme which incorporates first-principles (FP), tight-binding (TB), and molecular mechanical calculations. The key to this hybrid scheme is to find an explicit description of the FP-TB region coupling. We apply it to the atomic structure of a clean silicon atomic force microscope tip, and find the formation of a distinct atomic protrusion at the tip apex. The present study gives the reason why the atomic protrusion exits at the apex despite the fact that the atomic geometry of the very end of the tip is practically uncontrollable in the tip preparation.