Theoretical study of structural and optical properties of F-centers in tetragonal BaTiO3

Abstract:

Using the density functional theory (DFT) within the local density approximation (LDA) and a method based on the Hartree- Fock (HF) approximation, we study the structural, electronic and optical properties of F-centers (two electrons in an oxygen-vacancy) in the tetragonal lattice of the perovskite-type BaTiO<inf>3</inf> crystal. In this structure the F-center has two non-equivalent positions due to the two different O atoms; namely, the F-center situated in the Ti-O-Ti chains along the [001] polarization axes (V<inf>a</inf>⁰) and the F-center situated in the Ti-O-Ti chains within the x-y plane (V<inf>b</inf>⁰). Both cases are considered in our study. The obtained results point out that the crystal structure containing V<inf>a</inf>⁰ centre is energetically more stable than that of the V<inf>b</inf>⁰ center. The two electrons of the F-center are found to be localized on the two adjacent Ti ions and their ground state is composed mainly of Ti 3d<inf>z</inf>² atomic orbital. Besides, we have computed the allowed optical transitions for the F-center using the so-called ΔSCF method. As a result the obtained absorption energies are found to be equal to 1.47 eV for the V<inf>a</inf>⁰ center as well as 3.07 and 4.27 eV for the V<inf>b</inf>⁰ center.

Año de publicación:

2002

Keywords:

• Ferroelectric
• BaTiO 3
• DFT
• Hartree-Fock
• Structural and optical properties
• F-center
• BaTiO3
• Oxygen vacancy

Fuente:

scopus

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