title: Stability of rocksalt (111) polar surfaces: beyond the octopole.
abstract: Stable polar oxide surfaces must be simultaneously electrostatically compensated and in thermodynamic equilibrium with the environment. As a paradigm, the MgO(111)-p(2x2) reconstructed surface is shown to involve combinations of Mg-covered terminations with peculiar insulating electronic structure, favored in O-poor conditions, and the O-terminated octopole, stabler in more O-rich environments. Such a picture, which could not have been foreseen by either experiments or simulations separately, goes beyond the Wolf model and reconciles the theory with the experimental data taken in variable thermodynamic conditions.
authors.affiliation: Groupe de Physique des Solides, UMR 7588 CNRS and Universités Paris 6 - Paris 7, Campus de Boucicaut, 140 rue de Lourmel, 75015 Paris, France.
authors.forename: Fabio
authors.initials: F
authors.lastname: Finocchi
authors.forename: Antoine
authors.initials: A
authors.lastname: Barbier
authors.forename: Jacques
authors.initials: J
authors.lastname: Jupille
authors.forename: Claudine
authors.initials: C
authors.lastname: Noguera