Role of the Band Gap for the Interaction Energy of Coadsorbed Fragments

Abstract

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Effects of the cooperative interaction on the diffusion of hydrogen on MgO(100)

“…In particular, we investigate the activation energy (∆E a ), calculated relative to initial and final structures, and the differential adsorption energy of H atoms (δE ads,H ). As pointed out in our previous work, 26 the pairing energy (or cooperative binding) is large (∆E pairing around 2 eV). This makes the adsorption of an additional Ho that adsorbs on a configuration with an unpaired 1Hm (i.e.…”

“…S1), and it can partially be derived from our previous work. 26 In the following, we investigate the effects of the donor-acceptor interaction between the adsorbed atoms (H + /H − ) on the reaction path and transition state of hydrogen diffusion on MgO(100).…”

“…on 1Hm, 1Ho-2Hm) much more favorable than on a configuration with an already paired H (i.e., on 1Ho-1Hm). 26 For the 1Ho structure, the minimum energy path indicates that the structure of the transition state has the hydrogen atom in the bridge position (two Mg or two O atoms) at a distance of d = 2.56 Å relative to the two neighboring Mg atoms [ Fig. 1(c)].…”

“…It results in spontaneous ionization and the Fermi level shifts to the conduction band edge because an extra electron is added to the system. [25][26][27][28] When 2H are co-adsorbed, in the ground state configuration, one hydrogen atom binds a) Author to whom correspondence should be addressed: isabela.traistaru@ ccodn.ro and isabelac.man@gmail.com. Telephone: +4021 316 7900.…”

“…This effect is called interaction/cooperative/pairing energy (∆E pairing ) and has been shown to exist on a number of oxide surfaces and electron donor and acceptor fragments to have a one-to-one correlation with the value of the bandgap. 26 In this work, we go beyond the effects of the cooperative adsorption on the binding energy and we investigate the impact of co-adsorbates on H diffusion on a MgO(100) surface, which is an elementary step in surface chemical reactions. The diffusion of H has been previously studied but, so far, the effects of co-adsorption have not been considered.…”