Correlation between the Madelung field and the reactivity of the MgO low-coordinated surface sites

Abstract

We study correlations between Madelung constants, charges of surface ions, and chemical activity of low-coordinated sites of the MgO crystal surface with respect to dissociative adsorption of hydrogen. The ab initio Embedded Cluster model [Puchin et al., Phys. Rev. B 47, 6226 (1993)] employed in this study allowed us to reproduce correctly both short range and long range (Madelung) parts of the interaction between ions in a quantum cluster and the rest of the crystal. Our results show that sites having the same coordination numbers may have different properties, depending on values of Madelung constants. Lower Madelung constants correspond to lower ionicity, higher energy of H2 adsorption, stronger O–H and Mg–H bonds, and larger spatial separation of two adsorbed hydrogen atoms.

A theoretical approach for modeling reactivity at solid–liquid interfaces

“…This is important for an accurate representation of the cluster electron density, correct positions of the crystal electronic band edges with respect to vacuum, and redox potentials of molecular solutes. As described below and in our previous study, 26 several hundred point charges are often sufficient to approximate the Madelung potential in the cluster with an accuracy of about 1%. A self-consistent treatment of the solvent polarization can be achieved by using dielectric continuum solvation methods.…”

Reduction of benzaldehyde on alkaline earth metal oxides

“…In this case, the presence of surface adsorbed hydrogen over alkali earth metal oxides has been proved [16]. The experimental evidence that the low-coordination sites are responsible for H 2 dissociation has also been confirmed by theoretical investigations [17]. The presence of a totally dehydration surface is therefore necessary for both heterolytic dissociative hydrogen adsorption [16].…”

Metal Oxide Surfaces and Their Interactions with Aqueous Solutions and Microbial Organisms

“…In contrast, many experimental studies performed under UHV conditions with low concentrations of water at the interface show little or no indication of surface hydroxylation. 15 The extensive number of experimental 15,65,100,[102][103][104][105][107][108][109][110][768][769][770][771][772][773][774][775][776][777][778][779] and theoretical studies [96][97][98]106,748,754,763,775,[780][781][782][783][784][785][786][787][788][789][790][791][792][793] that probed the structure and reactivity of MgO (100) and the chemistry of water on MgO illustrates the complexity of this "simple" system. Empirical observations of molecular adsorption and chemidissociation vary depending on the experimental m...…”