Hartree-Fock studies of the ferroelectric perovskites

Abstract

Abstract. Within an ab-initio HF scheme, we use both Berry-phase calculations and supercell calculations in order to compute the dynamical charges for lattice dynamics and the electronic dielectric constant for KNbO 3 and BaTiO 3 . Comparison with experimental data indicates that HF provides a description of the electronic properties of this material whose accuracy is of the same order as the LDA one. There are however significant differences between the two sets of results, whose origin is scrutinized. Motivated by the study of surface and domain-boundary properties, we also present some results for BaTiO 3 slabs, including both genuinely isolated and periodically repeated slabs with different terminations. The capability of dealing with a genuinely isolated slab is a virtue of the localized-basis implementation adopted here. We demonstrate, amongst other things, the nontrivial dynamical-charge neutrality of BaTiO 3 [001] surfaces.

Theory of ferroelectrics: a vision for the next decade and beyond

“…Using plane waves and pseudopotentials, Padilla and Vanderbilt found an average relaxed surface energy of 1260 erg/cm 2 [50]. Hartree-Fock calculations using Gaussian basis sets gave 1690 erg/cm 2 (unrelaxed) [51]. The differences in basis sets as well as Hartree-Fock versus LDA may be responsible for the differences.…”

“…The isolated slab Hartree Fock study is the most straightforward to interpret, and they found results similar to bulk BaTiO 3 . The use of isolated, rather than periodic, slabs, greatly facilities interpretation of results for asymmetric or polar slabs [51].…”

Ab initioHartree-Fock Born effective charges of LiH, LiF, LiCl, NaF, and NaCl

“…For ionic systems, the HF method provides a powerful alternative in that it performs much better than the local-density approximation based schemes. 25,26 The other advantage of the HF method is that it can be systematically improved, both by perturbative as well as nonperturbative methods, to account for many-body effects. 27 Recently, we have developed a Wannier-functionbased ab initio HF approach to compute the ground-state properties of crystalline insulators.…”

“…This Berry-phase-based approach to macroscopic polarization of dielectrics has come to be known as the ''modern theory of polarization'' ͑MTP͒ in the current physics literature. 16 The MTP has been used both within the density-functional theory ͑DFT͒ based implementations, 2,3,13,[17][18][19][20][21][22] as well as the wave-function-based Hartee-Fock [23][24][25] ͑HF͒ formulations, to evaluate a variety of polarization-related properties.…”