Theoretical modelling of infrared spectra of the twinned lead zirconate

Abstract

The THz-frequency range dispersion of the complex dielectric permittivity tensor of antiferroelectric lead zirconate, associated with its multiple weak infrared active phonon modes, is modelled by the oscillator formula with parameters fully determined from the recently developed atomistic shell model. The resulting realistic dielectric function is used to estimate the far-infrared reflectivity spectra of a twinned lead zirconate crystal in the limit of narrow and wide domains. It is shown that in case of the sufficiently narrow domain widths, the effective-medium average permittivity shows additional modes identified as geometric resonances (i.e. extraneous excitations created by material interfaces), possibly distinguishable in suitable experiments.

Keywords:

• Domains
• infrared spectroscopy
• dielectric permittivity
• lead zirconate, shell model
• Born effective charge

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Grant Agency of the Czech Republic (GACR) [grant number 15-04121S] and the Grant Agency of the Czech Technical University in Prague No. SGS16/244/OHK4/3T/14.