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DF: Dielektrische Festkörper

DF 1: Elektrische und optische Eigenschaften I

DF 1.7: Talk

Monday, March 24, 2003, 11:50–12:10, HSZ/403

Electrical and optical properties of LiNbO₃ at room temperature — •Hassan Chaib, Tobias Otto, and Lukas M. Eng — Institute of Applied Photophysics, University of Technology Dresden, D-01062 Dresden, Germany

We present a theoretical approach for studying the electrical and optical properties of Lithium Niobate (LiNbO₃). The microscopic model bases on the orbital approximation in correlation with the dipole-dipole approximation and takes into account the anisotropy in the electronic polarizability and hyperpolarizability of all constituent ions, their ionic shifts as well as the crystalline deformations. The model was previously tested when calculating the bulk properties of mono-domain tetragonal BaTiO₃ and KNbO₃, i.e. the ferroelectricity and optical anisotropy as well as the electrooptical coefficients ^1,2. Furthermore the same model could be applied to successfully model the electrical and optical properties even within the 180^o domain wall in BaTiO₃ ³.
The calculation for LiNbO₃ shows that the experimental data of the spontaneous polarization and refractive indices at room temperature is successfully reproduced only when reconsidering the nonlinearity and anisotropy of the electronic polarizability and hyperpolarizability of the constituent ions, particularly that of the O²⁻-ions.

1 H. Chaib et al., Nonlin. Optics 23, 97 (1999)
2 H. Chaib et al., J. Phys.: Cond. Mat. 12, 2317 (2000)
3 H. Chaib et al., Phys. Stat. Sol. (b) 23, 250 (2002)