Polarization properties of KNbO: comparison between Hartree–Fock and density-functional calculations

Influence of Non-Stoichiometric Defects on Electrooptics in KNbO3

“…1 the band energy as calculated along the two main directions G±Z and G±L, corresponding to parallel and perpendicular directions relative to the thirdorder optical axis of the tetrahedral KNB single crystals. One can see that the general features of the band energy dispersion for the perfect crystals are in agreement with the data obtained by the other methods [16,17].…”

“…Comparison in the optical properties between calculated values and experi-820 I. V. Kityk et al mental data shows that our approach is appropriate. Thus the calculated bands are in agreement within 0.29 eV with the experimental data given by X-ray photoelectron spectroscopy [17]. The value of calculated energy gap was less than 3.52 eV comparing with 3.66 eV obtained from the absorption edge [17].…”

“…[17]. In the present paper, we perform a detailed calculation of the band electronic structure and the appropriate optical properties of KNB crystals using the self-consistent NCPP method within the LDA approximation of the densityfunctional theory (DFT) [18] with simultaneous orthogonalisation to the LCAO basis.…”

“…To calculate the particular EO coefficient r 22 , we put i j k 2 in Eq. (17). We have performed all calculations for the G-point of the BZ.…”

“…We have performed the calculations via Eqs. (17) and (18) for two shells (Nb±O 6 and K±O 6 ). The total value of the EO coefficient arising from all phonon, electron and electron±phonon contributions has been thus calculated.…”