Compton scattering study of lithium niobate: experimental and theoretical investigations

Ferroelectric material LiNbO₃ has definite importance because of its use in piezoelectric devices, waveguides, photo refractive devices, holographic memories, electro-optic modulators, nonlinear optical devices, etc. We have measured the experimental electron momentum density (EMD) of LiNbO₃ using 100 mCi ²⁴¹Am Compton spectrometer and compared with theoretical EMDs using linear combination of atomic orbitals (LCAO) with Perdew-Wang generalized gradient approximation (PWGGA). We found that Compton line shape deduced using LCAO-PWGGA gives a better agreement with the experimental profile than free atom profile. We also present electronic structure of LiNbO₃ using LCAO-PWGGA. We found energy band gap of 2.91 eV of LiNbO₃ showing its semiconductor nature. Upper valence band (VB) region is mainly formed by 2p states of 0 and 4d states of Nb. Negligible contribution is seen from 2s states of 0 in upper Nb. It is observed that conduction bands are majorly formed by Nb-4d states. (author)