title: Thermodynamic Stability of BiFeO3(0001) Surfaces from ab Initio Theory.
abstract: The relative stability of multiferroic BiFeO3(0001) surfaces, which is the (111) facet in the pseudocubic notation, with different stoichiometry is systematically studied by using ab initio thermodynamic approach in order to obtain insights into the stable surface terminations. We predict that under most chemical potential conditions the thermodynamically favored terminations for the negative and positive surfaces are -Bi-O2and -Fe-O3-Bi, respectively. The predicted difference in oxygen content between the negative and positive surfaces is consistent with experimental observations at the BiFeO3/metal interfaces ( Nat. Mater. , 2014 , 13 , 1019 , DOI: 10.1038/nmat4058 ; Adv. Mater. , 2015 , 27 , 6934 , DOI: 10.1002/adma.201502754 ). We determine the atomic geometries and electronic states as well as the magnetic properties for the negatively and positively polarized stable surfaces. Our results demonstrate that not only the stoichiometry and atomic geometries but also the electronic and magnetic properties of the BiFeO3(0001) surfaces show strong dependence on the ferroelectric polarization direction. Therefore, we expect that the surface physical and chemical properties of the BiFeO3(0001) surfaces can be easily tuned by an external electric field.
authors.affiliation: School of Materials Science and Engineering, Kunming University of Science and Technology , Kunming 650093, PR China.
authors.forename: Jian-Qing
authors.identifier: http://orcid.org/0000-0003-4352-0789
authors.initials: JQ
authors.lastname: Dai
authors.affiliation: School of Materials Science and Engineering, Kunming University of Science and Technology , Kunming 650093, PR China.
authors.forename: Jie-Wang
authors.initials: JW
authors.lastname: Xu
authors.affiliation: School of Materials Science and Engineering, Kunming University of Science and Technology , Kunming 650093, PR China.
authors.forename: Jian-Hui
authors.initials: JH
authors.lastname: Zhu
keywords: (0001); BiFeO3; ab initio calculations; polar surfaces; thermodynamic stability