  We present a detailed investigation of the structure and activity of extended
defects namely monoatomic steps on (1x1)-TiO2(110). Specifically, the two most
stable <001> and <1-11> step edges are considered. Employing an automated
genetic algorithm that samples a large number of candidates for each step edge,
more stable, reconstructed structures were found for the <1-11> step edge,
while the bulk truncated structures were recovered for the <001> step edge. We
demonstrate how oxygen vacancies along these defects have lower formation
energies than on flat terraces and how water and methanol molecules adsorb
dissociatively on reduced <1-11> step edges. Our findings are in agreement with
earlier experimental results and indicate an important contribution from step
edges to the reactivity of the TiO2(110) surface.
