Ab-initio calculations for the interpretation of scanning probe microscopy

Scanning tunneling microscope and atomic force microscope are both capable of imaging solid surfaces with atomic resolution. However, the relation of the tunneling current or atomic forces to the real atomic and electronic structure of the imaged surface is not straightforward. In order to facilitate the interpretation of data yielded by this microscopic methods, extensive ab-initio calculations will be performed, simulating the interaction of the scanning tip with selected types of surfaces. Relaxation of the tip and surface structure due to their interaction will be taken into account. Tunneling conductance and the interaction force will be calculated as functions of the tip position. Graphite and silicon surfaces covered with adsorbates as well as surfaces of metallic alloys will be chosen for the simulations. Results obtained for several plausible models of the probing tip will be compared. The possibilities of achieving chemical identification of individual atoms and performing deliberate atomic manipulations with the scanning tip will be explored.