title: Thermodynamic stability of stoichiometric LaFeO3and BiFeO3: a hybrid DFT study.
abstract: BiFeO3perovskite attracts great attention due to its multiferroic properties and potential use as a parent material for Bi1-xSrxFeO3-δand Bi1-xSrxFe1-yCoyO3-δsolid solutions in intermediate temperature cathodes of oxide fuel cells. Another iron-based LaFeO3perovskite is the end member for well-known solid solutions (La1-xSrxFe1-yCoyO3-δ) used for oxide fuel cells and other electrochemical devices. In this study an ab initio hybrid functional approach was used for the study of the thermodynamic stability of both LaFeO3and BiFeO3with respect to decompositions to binary oxides and to elements, as a function of temperature and oxygen pressure. The localized (LCAO) basis sets describing the crystalline electron wave functions were carefully re-optimized within the CRYSTAL09 computer code. The results obtained by considering Fe as an all-electron atom and within the effective core potential technique are compared in detail. Based on our calculations, the phase diagrams were constructed allowing us to predict the stability region of stoichiometric materials in terms of atomic chemical potentials. This permits determining the environmental conditions for the existence of stable BiFeO3and LaFeO3. These conditions were presented as contour maps of oxygen atoms' chemical potential as a function of temperature and partial pressure of oxygen gas. A similar analysis was also performed using the experimental Gibbs energies of formation. The obtained phase diagrams and contour maps are compared with the calculated ones.
authors.affiliation: Max Planck Institute for Solid State Research, Heisenbergstr. 1, Stuttgart 70569, Germany. eheif5719@sbcglobal.net eheif5719@twc.com.
authors.forename: Eugene
authors.identifier: http://orcid.org/0000-0002-1667-5104
authors.initials: E
authors.lastname: Heifets
authors.affiliation: Max Planck Institute for Solid State Research, Heisenbergstr. 1, Stuttgart 70569, Germany. eheif5719@sbcglobal.net eheif5719@twc.com and Institute for Solid State Physics, The University of Latvia, Riga, 8 Kengaraga str., Riga 1063, Latvia.
authors.forename: Eugene A
authors.initials: EA
authors.lastname: Kotomin
authors.affiliation: National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoye shosse 31, Moscow 115409, Russia and Photochemistry Center RAS Federal State Institution, Federal Research Center Crystallography and Photonics Russian Academy of Science, 7a Novatorov St., Moscow, 119421, Russia.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Bagaturyants
authors.affiliation: Max Planck Institute for Solid State Research, Heisenbergstr. 1, Stuttgart 70569, Germany. eheif5719@sbcglobal.net eheif5719@twc.com.
authors.forename: Joachim
authors.initials: J
authors.lastname: Maier