0000000000082791
AUTHOR
Driss Khatib
Étude théorique de la dynamique du réseau de PbTiO3 dans la phase quadratique
Resume La dynamique du reseau du titanate de plomb PbTiO 3 est etudiee en phase quadratique a l'aide d'un modele a coquille tenant compte des polarisabilites electroniques des ions de la maille elementaire et des interactions a longue et a courte portee. Les resultats de nos calculs mettent en evidence le role important joue par l'anisotropie de la polarisabilite electronique de l'oxygene. Il est montre aussi que les courbes de dispersion des phonons calculees dans la premiere zone de Brillouin sont en bon accord avec l'experience.
Theory of birefringence and spontaneous polarization in the tetragonal phase of PbTiO3 due to lattice deformation caused by the change of temperature
The microscopic mechanism of birefringence in the tetragonal phase of PbTiO3 is discussed taking account of the dipole-dipole interaction (dipole-dipole effect) due to the ionic and electronic polarizations of the crystal and the spontaneous Kerr effect as a cause of the strong local field acting on the constituent ions, where the lattice deformation due to the change of temperature is also considered. For the spontaneous polarization we use only the first effect. It is found that the birefringence and the spontaneous polarization are in good agreement with the experimental data.
Theory of spontaneous polarization and birefringence in the tetragonal phase of KNbO3
Abstract The microscopic mechanism of optical anisotropy in the tetragonal phase of KNbO3 is discussed taking account of the dipole-dipole effect due to the ionic and electronic polarizations of the crystal and the spontaneous Kerr effect. The last effect is a cause of the strong local field acting on the constituent ions. For the spontaneous polarization we use only the first effect. It is found that the birefringence and the spontaneous polarization are in good agreement with the experimental data.