Towards an accurate description of perovskite ferroelectrics: exchange and correlation effects

Abstract

Using the van der Waals density functional with C09 exchange (vdW-DF-C09), which has been applied to describing a wide range of dispersion-bound systems, we explore the physical properties of prototypical ABO3 bulk ferroelectric oxides. Surprisingly, vdW-DF-C09 provides a superior description of experimental values for lattice constants, polarization and bulk moduli, exhibiting similar accuracy to the modified Perdew-Burke-Erzenhoff functional which was designed specifically for bulk solids (PBEsol). The relative performance of vdW-DF-C09 is strongly linked to the form of the exchange enhancement factor which, like PBEsol, tends to behave like the gradient expansion approximation for small reduced gradients. These results suggest the general-purpose nature of the class of vdW-DF functionals, with particular consequences for predicting material functionality across dense and sparse matter regimes.

Towards photoferroic materials by design: recent progress and perspectives

“…The Berry phase formula can thus be used to calculate changes in polarization under structural deformations and the spontaneous polarization can be defined as the polarization relative to a nonferroelectric structural phase. Equation (1) has been applied to predict the spontaneous polarization of a wide range of ferroelectrics and yield reasonable agreement with experimental values [92], although the results can be somewhat dependent on the choice of exchange-correlation functional [81]. Moreover, the expression provides an easy way to calculate the Born effective charges [93], which determine the atomic displacements under an applied electric field and account for the splitting of longitudinal optical phonons at the Brillouin zone center [94].…”

Discovery of ABO3 perovskites as thermal barrier coatings through high-throughput first principles calculations

“…Automatic calculations are performed via our developed code adopting Vienna Ab initio Simulation Package (VASP.5.4.4) based on density functional theory (DFT) [14]. The generalized-gradient approximation (GGA-PBEsol) [15] is used as the exchange correlation functional in this work due to its good reproduction of experimental perovskite structures [16]. A 500 eV cutoff energy and a 4 × 4 × 4 k-points mesh over Brillouin zone (BZ) in Morhorst-Pack method are adopted [17].…”

Property control from polyhedral connectivity in ABO3 oxides

“…Polar distortions are intricately linked to the elastic properties of a material, 59 and polar phases of PbTiO 3 , BaTiO 3 , and KNbO 3 are known to have reduced bulk moduli compared to centrosymmetric phases. 60,61 Lines and Glass in their book Principles and Applications of Ferroelectrics and Related Materials 59 note that the direct coupling between optical soft modes and the acoustic modes gives rise to variations in the elastic constants with temperature on passing through the transition temperature. To the extent of our knowledge, however, there does not seem to be an accepted explanation for why the elastic constants (and therefore bulk modulus) would be different between the centrosymmetric and polar phases far away from the Curie temperature.…”