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M. Reticcioli, I. Sokolovic, M. Schmid, U. Diebold, M. Setvin, C. Franchini:
"Interplay between Adsorbates and Polarons: CO on Rutile TiO₂(110)";
Physical Review Letters, 122 (2019), 0168051 - 0168056.

Polaron formation plays a major role in determining the structural, electrical, and chemical properties ofionic crystals. Using a combination of first-principles calculations, scanning tunneling microscopy, andatomic force microscopy, we analyze the interaction of polarons with CO molecules adsorbed on the reducedrutile TiO2ð110Þsurface. Adsorbed CO shows attractive coupling with polarons in the surface layer, andrepulsive interaction with polarons in the subsurface layer. As a result, CO adsorption depends on thereduction state of the sample. For slightly reduced surfaces, many adsorption configurations with comparableadsorption energies exist and polarons reside in the subsurface layer. At strongly reduced surfaces, twoadsorption configurations dominate: either inside an oxygen vacancy, or at surface Ti5csites, coupled with asurface polaron. Similar conclusions are predicted for TiO2ð110Þsurfaces containing near-surface Tiinterstitials. These results show that polarons are of primary importance for understanding the performanceof polar semiconductors and transition metal oxides in catalysis and energy-related applications.