TiO2 , surface relaxation

It is comforting that the elemental rules for predicting surface terminations outlined in section 3.1.1. work so well for predicting the structure of the (1x1) terraces and the step edges of all the orientations of both rutile and anatase. The extensive theoretical work has helped to refine the understanding of surface relaxations, and the level of detail on the atomic geometry of the TiO2(110) surface is certainly comparable to that of certain elemental semiconductors or metals. 

Fig. 4. Model of the TiO2(110) surface. The relaxations of surface atoms, determined with SRXD are indicated [34]. The labels refer to the relaxations listed in Table 1.

In Fig. 15a, O atoms would move to the right and Ti atoms to the left. The net effect of these displacement is to increase the effective coordination of the 5-fold coordinated Ti atoms [109]. To my knowledge, no experimental data on relaxations of the TiO2(100)(lxl) surface exist. X-ray photoelectron and Auger electron diffraction were performed but are insensitive to the details of the surface structure [111]. 

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