Study of rutile (110) surface STM image via ab-initio simulation

First principle calculations based on DFT have been applied to study various properties of rutile (110) surface. We used a nine-layer slab model with stoichiometric formula of TiO₂ and the vacuum length of the cell fixed at 1.5 nm. The interactions between ionic core and valence electrons were represented by pesudopotentials. After analyzing the results, we found that an admixture bonding states existed in titanium dioxide: A stronger ionic bond accompanied by a weaker covalent bond between Ti and O. STM (Scanning tunneling microscope) image of Rutile (110) surface has been successfully simulated by DFT calculations, which was in accord with the Tersoff-Hamann's theory. A positive basis voltage of 2 V was added to simulate STM experimentd conditions in imaging process. The distance between tip and surface were also changed step by step. By analyzing the electron density map and DOS plot, it is clear that electron factors dominated the STM image of rutile (110) surface and the jut in the image corresponded to 5-coordinated Ti atom rather than the bridge oxygen on the top.