Abstract
Sparse-matter problems have compelled the development of methods to account for nonlocal, noncovalent interactions in density functional theory. These soft-matter functionals have been mostly focused on long range interactions, while many interesting problems in physics and chemistry (such as catalysis, self-assembly, solid-electrolyte interfaces) lie at the intersection between dense and sparse matter. Using the van der Waals density functional with C09 exchange (vdW-DF-C09), which has been applied in 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 as the gradient expansion approximation for small reduced gradients. These results emphasize the general-purpose nature of the class of vdW-DF functionals, with particular consequences for predicting material functionality across dense and sparse matter regimes.
