Density functional theory (DFT) has been regularly exploited for meticulous studying of complex surface interactions at a molecular orbital scale. However, DFT calculations usually yield inaccurate thermodynamics results that contradict experimental findings. A clear example is the CO adsorption puzzle caused by the wrong estimation of adsorption sites, especially for the (111) transition metal surfaces. The puzzle is still not fully resolved and a complete adsorption picture is yet to be reported. Herein, we demonstrate the reliability of DFT calculations for the study of local bond properties, despite the wrong energetics predictions. We also highlight the importance of considering a comprehensive analysis of all the possible adsorption sites over distinctive surface facets. Each surface facet, with its unique arrangement of atoms, results in a varying adsorbate behavior, although the same adsorption site is studied. Investigating these variations gives insights about the influence of surface atomic arrangement on the orbitals' interactions. Within the investigation, it is found that the varying density of orbitals, with the matching symmetry for interaction at different adsorption sites, affects the magnitude of orbital interaction, and thus, acts as an additional factor for determining the site preference. Based on the frontier (5Ïƒ and 2Ï€*) orbital energy description, calculated using RPBE functional, new perceptions to the understanding of the adsorption puzzle have been exposed. In addition, we emphasize the significance of considering a holistic analysis of adsorbate orbitals, not only limited to the main CO frontier orbitals. This approach leads to a better understanding of the surface bonding and CO final structure. This investigation can help in providing guidelines for innovating design principles for materials, based on the required adsorbate behavior and charge transport phenomena, to be used for catalysis and sensors applications.
MS in Physics
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(2019).First principles insights on CO adsorption on metal surfaces [Master's Thesis, the American University in Cairo]. AUC Knowledge Fountain.
Gameel, Kareem. First principles insights on CO adsorption on metal surfaces. 2019. American University in Cairo, Master's Thesis. AUC Knowledge Fountain.