First-principles study of high-field piezoelectricity in tetragonal PbTiO3

TL;DR

This study uses first-principles calculations to explore the nonlinear piezoelectric response of tetragonal PbTiO3 under high electric fields, revealing a nearly linear c/a ratio dependence up to 500 MV/m and significant non-linearities under different boundary conditions.

Contribution

It provides the first-principles analysis of high-field piezoelectricity in PbTiO3, highlighting the effects of boundary conditions on nonlinear response.

Findings

c/a ratio depends linearly on electric field up to 500 MV/m

High fields cause little saturation in piezoelectric response

Modified boundary conditions induce strong non-linearities

Abstract

We calculate from first principles the nonlinear piezoelectric response of ferroelectric PbTiO3 for the case of a polarization-enhancing electric field applied along the tetragonal axis. We focus mainly on the case of fixed in-plane lattice constants, corresponding to epitaxially constrained thin films. We find that the dependence of the c/a ratio on electric field is almost linear in the range up to 500 MV/m, with little saturation. This result contrasts with expectations from Landau-Devonshire approaches based on experimental results obtained at lower fields, but is in qualitative agreement with a recent experiment in which higher fields were attained using pulsed-field methods. We also study cases in which the in-plane epitaxy constraint is removed, or an artificial negative pressure is applied, or both. These calculations demonstrate that PbTiO3 can show a strikingly non-linear piezoelectric response under modified elastic boundary conditions.