The pseudoatomic orbital basis: electronic accuracy and soft-mode distortions in ABO${}_3$ perovskites

Abstract

The perovskite oxides are known to be susceptible to structural distortions over a long wavelength when compared to their parent cubic structures. From an ab initio simulation perspective, this requires accurate calculations including many thousands of atoms; a task well beyond the remit of traditional plane wave-based density functional theory (DFT). We suggest that this void can be filled using the methodology implemented in the large-scale DFT code, CONQUEST, using a local pseudoatomic orbital (PAO) basis. Whilst this basis has been tested before for some structural and energetic properties, none have treated the most fundamental quantity to the theory, the charge density $n(\mathbf{r})$ itself. An accurate description of $n(\mathbf{r})$ is vital to the perovskite oxides due to the crucial role played by short-range restoring forces (characterised by bond covalency) and long range coulomb forces as suggested by the soft-mode theory of Cochran and Anderson. We find that modestly sized basis sets of PAOs can reproduce the plane-wave charge density to a total integrated error of better than 0.5% and provide Bader partitioned ionic charges, volumes and average charge densities to similar degree of accuracy. Further, the multi-mode antiferroelectric distortion of PbZrO${}_3$ and its associated energetics are reproduced by better than 99% when compared to plane-waves. This work suggests that electronic structure calculations using efficient and compact basis sets of pseudoatomic orbitals can achieve the same accuracy as high cutoff energy plane-wave calculations. When paired with the CONQUEST code, calculations with high electronic and structural accuracy can now be performed on many thousands of atoms, even on systems as delicate as the perovskite oxides.

References in corpus (10)

• Restoring the density-gradient expansion for exchange in solids and surfaces
• Generalized gradient approximation for solids and their surfaces
• Accurate and efficient algorithm for Bader charge integration
• Libxc: a library of exchange and correlation functionals for density functional theory
• Recent progress with large-scale ab initio calculations: the CONQUEST code
• Large scale and linear scaling DFT with the CONQUEST code
• First-principles study of the multi-mode anti-ferroelectric transition of PbZrO3
• Highly accurate local basis sets for large-scale DFT calculations in CONQUEST
• Structure-Property Relation of SrTiO3-LaAlO3 Interfaces
• First principles soft mode lattice dynamics of PbZr${}_{0.5}$Ti${}_{0.5}$O${}_3$ and shortcomings of the virtual crystal approximation

Cited by in corpus (2)

• Polar morphologies from first principles: PbTiO${}_3$ films on SrTiO${}_3$ substrates and the $p(2\times \Lambda )$ surface reconstruction
• Origin of ferroelectric domain wall alignment with surface trenches in ultrathin films