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

• Published in: The European physical journal. B, Condensed matter physics Vol. 57; no. 3; pp. 291 - 297
• Main Authors: RAKOTOVELO, G, MOUSSOUNDA, P. S, HAROUN, M. F, LEGARE, P, RAKOTOMAHEVITRA, A, PARLEBAS, J. C
• Format: Journal Article
• Language: English
• Published: Les Ulis Springer 01.01.2007; Berlin EDP sciences; Springer Nature B.V; Springer-Verlag
• Subjects: Adsorption; Barium oxides; Barium titanates; Center of gravity; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Density functional theory; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Impurity and defect levels; energy states of adsorbed species; Kinetic energy; Mathematical analysis; Perovskite structure; Perovskites; Physics; Scanning tunneling microscopy; Solid surfaces and solid-solid interfaces; Surface and interface electron states; Surface chemistry; Surface structure and topography; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Titanium dioxide; Oxygen; Surface electron state; Interatomic interaction; Barium titanates; Perovskites; Coverage rate; Surface structure; Scanning tunneling microscopy; Surface termination; Adsorption; Density functional method; Adsorption structure; Ab initio calculations
• ISSN: 1434-6028; 1434-6036
• DOI: 10.1140/epjb/e2007-00163-x

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.