Heifets Eugene, Kotomin Eugene A, Bagaturyants Alexander A, Maier Joachim
Max Planck Institute for Solid State Research, Heisenbergstr. 1, Stuttgart 70569, Germany.
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.
Phys Chem Chem Phys. 2017 Feb 1;19(5):3738-3755. doi: 10.1039/c6cp07986e.
BiFeO perovskite attracts great attention due to its multiferroic properties and potential use as a parent material for BiSrFeO and BiSrFeCoO solid solutions in intermediate temperature cathodes of oxide fuel cells. Another iron-based LaFeO perovskite is the end member for well-known solid solutions (LaSrFeCoO) 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 LaFeO and BiFeO with 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 BiFeO and LaFeO. 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.
BiFeO钙钛矿因其多铁性特性以及作为BiSrFeO和BiSrFeCoO固溶体的母体材料在氧化物燃料电池中温阴极的潜在用途而备受关注。另一种铁基LaFeO钙钛矿是用于氧化物燃料电池和其他电化学装置的著名固溶体（LaSrFeCoO）的端元。在本研究中，采用了一种从头算混合泛函方法来研究LaFeO和BiFeO相对于分解为二元氧化物和元素的热力学稳定性，作为温度和氧压的函数。在CRYSTAL09计算机代码中仔细重新优化了描述晶体电子波函数的局域（LCAO）基组。详细比较了将Fe视为全电子原子以及在有效核势技术下获得的结果。基于我们的计算，构建了相图，使我们能够根据原子化学势预测化学计量材料的稳定区域。这允许确定稳定的BiFeO和LaFeO存在的环境条件。这些条件以氧原子化学势作为温度和氧气分压函数的等高线图形式呈现。还使用实验生成吉布斯自由能进行了类似的分析。将获得的相图和等高线图与计算得到的进行了比较。
