Surface sensitivity in lithium-doping of MgO: A density functional theory study with correction for on-site Coulomb interactions

Reference:

Scanlon, D. O., Walsh, A., Morgan, B. J., Nolan, M., Fearon, J. and Watson, G. W., 2007. Surface sensitivity in lithium-doping of MgO: A density functional theory study with correction for on-site Coulomb interactions. Journal of Physical Chemistry C, 111 (22), pp. 7971-7979.

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Official URL:

http://dx.doi.org/10.1021/jp070200y

Abstract

Catalytic conversion of methane to higher hydrocarbons takes place on lithium-doped MgO. To date, investigations of the Li-doping process have been confined to the bulk and the ( 100) surface. In this paper, we describe an investigation of the surface dependence of Li-doping of MgO through an in-depth study of the ( 100), ( 110), and ( 111) low index surfaces using density functional theory with correction for on-site Coulomb interactions (DFT+U). Three competing defect configurations were investigated on each of the surfaces; substitution of Li for Mg with the formation of a compensating oxygen hole state, substitution of Li for Mg with the addition of a Li surface interstitial and the clustering of two Li ions with the formation of a neutral [Li'(Mg) VO Li'(Mg)] oxygen vacancy. Our results demonstrate that the energetics associated with the Li-doping of MgO are strongly surface dependent. On the ( 100) surface, there is an energy cost associated with Li-doping, whereas on the ( 110) and ( 111) surfaces Li-doping is energetically favored. The implications of the results for the catalytic activity of the different surface terminations of MgO are discussed.

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