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.