First-principles study ofPbTiO3under uniaxial strains and stresses

Abstract

The behavior of PbTiO3 under uniaxial strains and stresses is investigated from first-principles calculations within density functional theory. We show that irrespectively of the uniaxial mechanical constraint applied, the system keeps a purely ferroelectric ground-state, with the polarization aligned either along the constraint direction (F Ez phase) or along one of the pseudo-cubic axis perpendicular to it (F Ex phase). This contrasts with the cases of isotropic or biaxial mechanical constraints for which novel phases combining ferroelectic and antiferrodistortive motions have been previously reported. Under uniaxial strain, PbTiO3 switched from a F Ex ground state under compressive strain to F Ez ground-state under tensile strain, beyond a critical strain η c zz ≈ +1%. Under uniaxial stress, PbTiO3 exhibits either a F Ex ground state under compression (σzz < 0) or a F Ez ground state under tension (σzz > 0). Here, however, an abrupt jump of the structural parameters is also predicted under both compressive and tensile stresses at critical values σzz ≈ +2 GPa and −8 GPa. This behavior appears similar to that predicted under negative isotropic pressure and might reveal practically useful to enhance the piezoelectric response in nanodevices.

Calculation of strained BaTiO3 with different exchange correlation functionals examined with criterion by Ginzburg-Landau theory, uncovering expressions by crystallographic parameters

“…Specifically, the lattice symmetry of the equilibrium phase at 0 K of BaTiO 3 and many other ferroelectric oxides is different from that at RT, whereas ab initio calculations are generally for 0 K. For example, benchmark tests of ab initio calculations of ferroelectrics are mostly comparisons between calculations for 0 K and experiments at RT for stressfree cases, 10,11,26,27 with the notable exception of PbTiO 3 . 28 Here, BaTiO 3 and SrTiO 3 have special significance for theoretical comparisons due to the critical dependence of the experimental values on sample quality 12,13 and the availability of many reports of experiments using high-quality single crystals. For example, the high quality of these crystals is evidenced in the high transparency used in electro-optics and the observations of the negative carrier type (n-type) conduction by oxygen vacancy.…”

Finite-strain Landau theory applied to the high-pressure phase transition of lead titanate

“…It was the discovery of this transition [1], which occurs only at extreme pressures up to 125 GPa and temperatures of some 2500 K, that finally elucidated the unusual seismic properties of the earth's core-mantle D boundary layer. In addition to external hydrostatic pressure [2], electronic, magnetic, and optical properties of materials may also be strongly affected by chemical pressure [3] or uniaxial stress [4]. High pressure also plays an important role in the synthesis of bulk multiferroic materials and provides insight into the complex interplay between magnetic and electronic properties and structural instabilities [5].…”

Principles of surface potential estimation in mixed electrolyte solutions: Taking into account dielectric saturation

“…Although dielectric saturation is only important within the first hydration shell of the ion, it is non-negligible for ions in water [24]. The dielectric saturation of water strongly affects the EDL capacitance of an electrolytically top-gated graphene due to the strong electric field near the surface [20,25,26]. Therefore, the electrical potential and structure of EDL can be strongly affected by the dielectric saturation at the charged interfaces.…”