(209b) Structural and Stability Trends in Single (ABO3) Perovskite Oxides from DFT-Optimized Bond Valence Structures

Ternary perovskite oxides (ABO₃) are a diverse class of technically important materials that exhibit exceptional properties for a variety of applications; as such, ternary perovskite material properties have been characterized in several high-throughput density functional theory (DFT) investigations. To ensure computational tractability, however, these previous investigations employ structural and stability approximations that are not rigorously supported. Neglecting these assumptions, we report a comprehensive investigation of 200 experimental ABO₃ compositions generated in all possible ternary perovskite geometries— as dictated by the 11 unique Glazer tilts— and optimized with DFT. Glazer tilt enumeration was performed with the Structure Prediction and Diagnostic Software (SPuDS) optimization package— which uses a bond valence method (BVM) based global instability index (GII) minimization procedure to predict octahedral (BO₆) tilting— and relaxed with GGA+U parameters compatible with the Materials Project (MP) database. We report a general linear correlation between GII and DFT energy that enables GII minimized structures to predict DFT optimized structures, particularly those that exhibit significant octahedral tilting. ~95% of DFT predicted ground states arise from the heavily distorted a-b+a- (orthorhombic) Glazer tilt, verifying that BO₆ distortions are the primary mode of stabilization in these compositions. Furthermore, we define the “energetic well depth” to be the difference between the undistorted a0a0a0 (cubic) geometry and the DFT predicted ground state, and show that linear scaling of the well depth energy predicts the decomposition enthalpy of the ground state— computed relative to MP tabulated competing phases— with RMSE = 40 meV/atom. By leveraging this relationship and slightly modifying the GII minimization procedure used by SPuDS to improve cubic lattice predictions, stability can be rapidly and accurately predicted from a single DFT optimization of the 5-atom cubic geometry. This study thereby constitutes the first time an integrated SPuDS+DFT scheme has been used to examine perovskite oxides, and represents a valuable addition to the growing arsenal of high-throughput investigative tools for targeted ABO₃ applications.