| Autor: |
Prates Ramalho JP; Departamento de Química, Centro de Química de Évora e Centro Hercules, Universidade de Évora, R. Romão Ramalho, 59, 7000 Évora, Portugal., Illas F; Departament de Ciència dels Materials i Química Física & Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, C/Martí i Franquès 1, 08028 Barcelona, Spain., Gomes JR; CICECO, Departamento de Química, Universidade de Aveiro, Campus Universitário de Santiago, P-3810-193 Aveiro, Portugal. jrgomes@ua.pt. |
| Abstrakt: |
The geometry, energy and stretching frequency of carbon monoxide on the rutile TiO 2 (110) surface for coverages between 0.125 and 1.5 ML are investigated by means of density functional theory calculations. Four different approaches were considered, namely, the PBE exchange-correlation functional and the PBE-D2, vdW-DF and vdW-DF2 methods incorporating van der Waals dispersion interactions of different theoretical complexity and empiricism. It is found that upon the increase of the surface coverage, the adsorption becomes less favorable due to lateral destabilizing interactions between adsorbed molecules. The preferred geometry for CO changes from an upright configuration at 0.125 ML to tilted configurations at 1.5 ML and the tilting of the C-O axis from the surface normal increases with the increase of the surface coverage. At 1 ML, all computational approaches predict alternate tilted configurations which contradict the interpretation of recent experimental infrared reflection-absorption spectroscopic findings suggesting upright CO geometries. Encouragingly, a very good agreement between calculated and experimental shifts of the C-O stretching frequency of adsorbed CO at different coverages with respect to gaseous CO species was reached. |
