Figure 3. Four different sites of the MgO (100) surface.
Branda et al. [45] found that dissociative adsorption occurs at the sites with defects (edge and apical) resulting in the consequent H transfer from the OH group in ethanol to the O atom of the MgO surface. However, when ethanol is adsorbed on the surface without defects (terrace) two bonds are formed: 1) a hydrogen bond between the H of the ethanol molecule and an O of the surface; and 2) an interaction between a Mg atom of the surface and the O of ethanol. In the present study, we also considered terrace and O- and Mg-apical ethanol adsorption. In agreement with the result of Branda et al. ,[45] we found that nondissociative adsorption of ethanol occurs on the terrace site. However, the adsorption of ethanol molecule on the apical sites is dissociative only in the O-apical case while no ethanol dissociation occurs when ethanol is adsorbed on the Mg-apical site. The computed absorption energies (E ads) are -21.0, -29.0 and -37.9 kcal/mol for the terrace, Mg-apical, and O-apical sites, respectively.