Adsorption of CO on MgO supported alkali monolayers: a periodic density functional local density approximation and generalized gradient approximation study

• Published in: Surface science Vol. 445; no. 2-3; pp. 495 - 505
• Main Authors: Snyder, James A., Jaffe, John E., Lin, Zijing, Hess, Anthony C., Gutowski, Maciej
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 20.01.2000; Amsterdam Elsevier Science; New York, NY
• Subjects: Adatoms; Alkali metal monolayers; Carbon monoxide; Catalysis; Chemisorption; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Density functional calculations; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Impurity and defect levels; energy states of adsorbed species; Magnesium oxide; Physics; Surface and interface electron states; Alkali metal monolayers; Chemisorption; Magnesium oxide; Adatoms; Density functional calculations; Carbon monoxide; Catalysis; Inorganic compounds; Theoretical study; Electron transfer; Electronic density of states; Preadsorption; Electronic structure; Sodium; Binding energy; Adsorbed state; Vibrational modes; Magnesium oxides; Density functional method; Potassium; Local density approximation
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/S0039-6028(99)01120-6

The adsorption of CO on the MgO supported Na and K monolayers was investigated using a periodic density functional method. We found that the cooperative (non-pairwise) interaction present among the three constituents of the complex system, the MgO slab, the alkali metal monolayer, and the CO monolayer, is very small and that the only role of MgO is to support the alkali metal monolayer. Our calculations predict weakening of the CO bond due to the presence of the alkali metal monolayer, reflected by an elongation of the CO bond by 0.005Å and a redshift of the CO stretching frequency by ca. 30cm−1 in comparison with the corresponding gas phase values. The calculated density of states for the Mg⋯M, CO, and Mg⋯M⋯CO systems (M=Na, K) indicates that the electron transfer from the valence band of the alkali metal to the antibonding π∗ orbital of CO is the source of the CO bond weakening. Our estimate of the binding energy for CO on the MgO⋯M substrate is 5.1 and 5.0kcal/mol for M=Na and K, respectively.