First-principles study of the influence of (110) strain on the ferroelectric trends of TiO$_2$

TL;DR

This study uses first-principles density functional theory to analyze how uniaxial (110) strain influences ferroelectric properties and phase transitions in TiO₂ (rutile), revealing strain-induced ferroelectric phases and phonon behavior.

Contribution

It provides a comparative analysis of ferroelectric trends in TiO₂ under strain using two DFT implementations, confirming phase transition predictions with phonon calculations.

Findings

Ferroelectric phase appears under expansive (110) strain.

Soft polar modes emerge in strained TiO₂.

Consistent results from VASP and PWscf methods.

Abstract

We investigate the impact of uniaxial strain on atomic shifts, dipolar interactions, polarization and electric permittivity in TiO$_2$ (rutile) by using two different implementations of density functional theory. It is shown that calculations using the Vienna ab inito simulation package (VASP) and the plane-wave self-consistent field method (PWscf) yield qualitatively the same atomic relaxations and ferroelectric trends under strain. The phonon dispersion curves of unstrained and strained TiO$_2$ (rutile) obtained by employing the linear response method confirm previous calculations of the giant LO-TO splitting and the appearance of soft polar modes. A second order phase transition into a ferroelectric phase with polarization along (110) appears under expansive strain in (110) direction.