Electron Spectroscopy and the Electronic Structure of KNbO₃: First Principle Calculations

Abstract

Cataloged from PDF version of article.The electronic structures of KNbO(3)were calculated within the density functional theory, and their evolution was analyzed as the crystal-field symmetry changes from cubic to rhombohedral via tetragonal phase. We carried out electron-energy loss spectroscopy experiments by using synchrotron radiation and compared the results with the theoretical spectra calculated within Density Functional Theory. The dominant role of the NbO(6)octahedra in the formation of the energy spectra of KNbO(3)compound was demonstrated. The anomalous behavior of plasmons in ferroelectrics was exhibited by the function representing the characteristic energy loss in the region of phase transition

XYO3 (X = K, Na; Y = Nb, Ta) based superlattices for photocatalysis

“…Åand the other theoretical results [45][46][47]. The obtained lattice constants for cubic KTaO 3 are a ¼ b ¼ c ¼ 4.030 Å, which are well consistent with the previous theoretical reports [28,48,49].…”

Consistent Atomic Geometries and Electronic Structure of Five Phases of Potassium Niobate from Density-Functional Theory

“…For this reason, KNbO 3 is widely used in nonlinear optics and holographic applications, where it represents a viable alternative to the more diffused LiNbO 3 . Due to its technological importance, pure and defective KNbO 3 has been subject to many experimental [8][9][10][11][12] and theoretical [13][14][15][16][17][18][19] studies. The previous theoretical investigations were typically aimed at the description of the ground-state structure and the identification of defect centers relevant for the optical properties.…”

Effect of epitaxy on interband transitions in ferroelectric KNbO3

“…The difference between the film and the crystal is even more obvious in the spectra of ε 2 (E) as seen from figures 3(b) and (d). It should be mentioned that band-structure calculations have been carried out for the paraelectric cubic phase [37][38][39][40][41][42] and also for the tetragonal and the rhombohedral phases of KNO [41,42]. The calculations indicate practically similar band structures for all these phases [41,42].…”

“…The calculated band structure is practically insensitive to the calculation method and crystal phase [37][38][39][40][41][42]. The main interband transitions determining the dielectric function of KNO in the spectral range of 3-10 eV have been ascribed to those at the X point with energies of approximately 5 eV and above 7 eV, at the Γ point at around 6 eV, and at the M point at approximately 9 eV [40,42]. The broad dielectric peaks at 4-5 eV in the KNO crystal and the film may therefore be related to optical transitions at the X point of the BZ.…”