Eur. Phys. J. B 57, 291-297 (2007)
https://doi.org/10.1140/epjb/e2007-00163-x

DFT study of BaTiO₃ (001) surface with O and O₂ adsorption

¹ Laboratoire des Matériaux, Surfaces et Procédés pour la Catalyse (LMSPC), UMR 7515, CNRS-ECPM, Université Louis Pasteur, 25 rue Becquerel, 67087 Strasbourg Cedex 2, France
² Département de Physique, Faculté des Sciences, Université de Mahajanga, BP 652, 401 Mahajanga, Madagascar
³ Groupe de Simulations Numériques en Magnétisme et Catalyse, Département de Physique, Faculté des Sciences, Université Marien Ngouabi, BP, 00069 Brazzaville, Congo
⁴ Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), UMR 7504, CNRS, Université Louis Pasteur, BP 43, 23 rue du Loess, 67034 Strasbourg Cedex 2, France

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

Received: 15 December 2006
Revised: 20 March 2007
Published online: 6 June 2007

Abstract

Progress of scanning tunneling microscopy (STM) allowed to handle various molecules adsorbed on a given surface. New concepts emerged with molecules on surfaces considered as nano machines by themselves. In this context, a thorough knowledge of surfaces and adsorbed molecules at an atomic scale is thus particularly invaluable. In this work, within the framework of density functional theory (DFT), we present an electronic and structural ab initio study of a BaTiO₃ (001) surface (perovskite structure) in its paraelectric phase. As far as we know the atomic and molecular adsorption of oxygen at surface is then analyzed for the first time in the literature. Relaxation is taken into account for several layers. Its analysis for a depth of at least four layers enables us to conclude that a reasonable approximation for a BaTiO₃ (001) surface is provided with a slab made up of nine plans. The relative stability of two possible terminations is considered. By using a kinetic energy cut off of 400 eV, we found that a surface with BaO termination is more stable than with TiO₂ termination. Consequently, a surface with BaO termination was chosen to adsorb either O atom or O₂ molecule and the corresponding calculations were performed with a coverage 1 on a (1×1) cell. A series of cases with O₂ molecule adsorbed in various geometrical configurations are also analyzed. For O₂, the most favorable adsorption is obtained when the molecule is placed horizontally, with its axis, directed along the Ba-Ba axis and with its centre of gravity located above a Ba atom. The corresponding value of the adsorption energy is -9.70 eV per molecule (-4.85 eV per O atom). The molecule is then rather extended since the O–O distance measures 1.829 Å. By comparison, the adsorption energy of an O atom directly located above a Ba atom is only -3.50 eV. Therefore we are allowed to conclude that the O–O interaction stabilizes atomic adsorption. Also the local densities of states (LDOS) corresponding to various situations are discussed in the present paper. Up to now, we are not aware of experimental data to be compared to our calculated results.