First Row Transition Metal Atom Adsorption On-Top of F°_s Defects of a MgO(100) Surface

Abstract

We performed periodic density functional calculations to study the reactivity of F°s defects on MgO(100) toward the first row of transition metal atoms at low coverage. The F°s center interaction strength with the first row of transition metal atoms is explained by the filling of bonding and antibonding orbitals and by the respective positions of the metal and vacancy levels. The vacancy levels are those of a dummy atom with a diffuse s-type orbital and empty p-type orbitals. Under adsorption, most of the metal atoms maintain their atomic configuration. Exceptions concern Ti, Co, and Ni that have different spin states. Across the period, the adsorption energy exhibits two maxima. The largest metal adsorption energies are found for Ti and V on one hand and Co, Ni, and Cu on the other hand. For these atoms, the highest antibonding σ-orbital is empty and the occupancy of π-orbitals provides additional stability. Interactions of metal orbitals of appropriate symmetry with empty p-type vacancy orbitals and surface Mg 2+ orbitals yield stabilization.

First-row transition metal atoms adsorption on rutile TiO2(110) surface

“…Let us now compare metal adsorption on TiO 2 with that on the F°site of an O defective MgO(100) surface [6] taking for reference the adsorption on the perfect MgO(100) surface; we have both cases an increase of the adsorption energy due to high-HOMO levels. For the adsorption on the F°site, the increase relative to the perfect MgO surface is only due to a higher HOMO, the F°center being a stronger donor than the surface oxygen.…”

“…In spite of the difficulty of calculating E atom , such definition is necessary to focus on the interaction between the surface and a single metal atom. This definition has also been used for similar studies on MgO(100) [5][6][7]. E system is the spinpolarized total energy of the whole system (adsorbate/ substrate).…”

“…We have recently presented investigations on the MgO(100) surface [5][6][7] because of its simple and stable structure that offers a reference case for modeling. Metal adsorption at low coverage on this oxide occurs on the top of surface oxygen and this is suitable for a detailed MO analysis based on local atomic orbitals.…”

“…As for the studies on MgO(100) [5][6][7], we investigate transition metal adsorption for the first-row transition metals of the Mendeleev table. As in our previous studies, we also consider K and Ca being very electropositive, they are both able to significantly reduce the support.…”

Alkali metal atom adsorption on-top of the F s 0 defective center of MgO(001) surface

“…Table 1 summarizes the adsorption energies of alkali metal atom on top of the F 0 s center of MgO(001), and the distances of the alkali metal atom to the average surface plane and to the nearest magnesium atoms. The adsorption energy for all the alkali atoms on top of the F 0 s center is more or less smaller than that of the most transition metals on the same MgO(001) site [12] . The trend of the decreasing adsorption energy from light atoms to heavy atoms except the cesium atom which will be discussed later is observed.…”