First-principles investigation of ferroelectricity in epitaxially strained ${\mathrm{Pb}}_{2}\mathrm{Ti}{\mathrm{O}}_{4}$

Rapid Communication

First-principles investigation of ferroelectricity in epitaxially strained ${Pb}_{2} Ti O_{4}$

Craig J. Fennie and Karin M. Rabe

Phys. Rev. B 71, 100102(R) – Published 28 March 2005

Abstract

The structure and polarization of the as-yet hypothetical Ruddlesden–Popper compound ${Pb}_{2} Ti O_{4}$ are investigated within density-functional theory. Zone center phonons of the high-symmetry $K_{2} Ni F_{4}$ -type reference structure, space group I4/mmm, were calculated. At the theoretical ground-state lattice constants, there is one unstable infrared-active phonon. This phonon freezes in to give the I2mm ferroelectric state. As a function of epitaxial strain, two additional ferroelectric phases are found, with space groups I4mm and F2mm at compressive and tensile strains, respectively.