Eur. Phys. J. B 78, 353-358 (2010)
https://doi.org/10.1140/epjb/e2010-10680-0

Adsorption and co-adsorption of CH₃ and H on flat and defective nickel (111) surfaces

¹ Laboratoire des Matériaux, Surfaces et Procédés pour la Catalyse (LMSPC is a partner of the European Laboratory for Catalysis and Surface Science (ELCASS).) , UMR 7515, CNRS-ECPM, Université de Strasbourg, 25 rue Becquerel, 67087 Strasbourg Cedex 2, France
² Groupe de Simulations Numériques en Magnétisme et Catalyse, Département de Physique, Faculté des Sciences, Université Marien NGouabi, BP 69, Brazzaville, Congo
³ Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), UMR 7504 CNRS-UDS, Université de Strasbourg, 23 rue du Loess, BP 43, 67034 Strasbourg Cedex 2, France

Corresponding author: ^b parlebas@ipcms.u-strasbg.fr

Received: 6 September 2010
Published online: 22 November 2010

Abstract

We use a periodic density functional theory (DFT) code to study the adsorption of CH₃ and H, as well as their co-adsorption on a Ni(111) surface with and without Ni ad-atom, at a surface coverage of 0.25 monolayer (ML). We systematically investigate the site preference for CH₃ and H. Then we combine CH₃ and H in many co-adsorbed configurations on both surfaces. Methyl and hydrogen adsorption on a flat Ni(111) surface favours the hollow site over the top site. The presence of a Ni ad-atom stabilizes the adsorption of CH₃ better than a flat surface, while hydrogen is more stable on a flat Ni(111) surface. When H and CH₃ are co-adsorbed at nearest Ni neighbours on the (111) surface, their interaction is always repulsive. However, the dissociative adsorption of CH₄ is stabilised when the fragments are infinitely separated. For the co-adsorbed fragments CH₃ and H, in the presence of an ad-atom, the repulsive interaction is lowered, so that the dissociative form of CH₄ is locally stable.