Infrared spectroscopy in KNbO<sub>3</sub>through the successive ferroelectric phase transitions

Fontana, M.D.; Metrat, G.; Servoin, J. L.; Gervais, F.

doi:10.1088/0022-3719/17/3/020

Cited by 242 publications

(135 citation statements)

References 39 publications

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“…Similar calculations have been done earlier by other methods, 5,6,8 and the experimental data (obtained mostly by infrared reflectivity measurements 32,33 ) are available. We performed the calculations for a lattice constant a = 3.997Å (that is based on an experimental perovskite cell volume extrapolated to zero temperature) within a conventional frozen-phonon scheme, using the 2 × 2 × 2 LUC.…”

Section: B γ-To Frozen Phonons In the Cubic Phasesupporting

confidence: 54%

“…The general symmetry relations between the Γ phonon modes in the cubic and rhombohedral phases may be found, e.g., in Ref. 32. We consider in the present work only three A 1 modes, which originate from the T 1u block of the cubic phase, as the crystal symmetry lowers and all the soft modes become stabilized.…”

Section: Displacements and Phonons In The Rhombohedral Phasementioning

confidence: 91%

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Semiempirical Hartree-Fock calculations forKNbO3

1996

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In applying the semiempirical intermediate neglect of differential overlap (INDO) method based on the Hartree-Fock formalism to a cubic perovskite-based ferroelectric material KNbO3, it was demonstrated that the accuracy of the method is sufficient for adequately describing the small energy differences related to the ferroelectric instability. The choice of INDO parameters has been done for a system containing Nb. Based on the parametrization proposed, the electronic structure, equilibrium ground state structure of the orthorhombic and rhombohedral phases, and Γ-TO phonon frequencies in cubic and rhombohedral phases of KNbO3 were calculated and found to be in good agreement with the experimental data and with the first-principles calculations available.

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Section: B γ-To Frozen Phonons In the Cubic Phasesupporting

confidence: 54%

Section: Displacements and Phonons In The Rhombohedral Phasementioning

confidence: 91%

Semiempirical Hartree-Fock calculations forKNbO3

1996

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“…In this same work the Berry-phase theory of macroscopic polarization [5,6] is implemented within the HF scheme, using first-principles ingredients. Perhaps the most interesting result that has emerged is that the calculated HF spontaneous polarization of KNbO 3 in its tetragonal phase is 0.34 C/m 2 , quite close to the experimental value [7], which is 0.37 C/m 2 , as well as previous LDA results [8][9][10], which are between 0.33 and 0.40 C/m 2 .…”

Section: Introductionsupporting

confidence: 84%

Hartree-Fock studies of the ferroelectric perovskites

Fu¹,

Yaschenko²,

Resca³

et al. 1998

AIP Conference Proceedings

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Abstract. Within an ab-initio HF scheme, we use both Berry-phase calculations and supercell calculations in order to compute the dynamical charges for lattice dynamics and the electronic dielectric constant for KNbO 3 and BaTiO 3 . Comparison with experimental data indicates that HF provides a description of the electronic properties of this material whose accuracy is of the same order as the LDA one. There are however significant differences between the two sets of results, whose origin is scrutinized. Motivated by the study of surface and domain-boundary properties, we also present some results for BaTiO 3 slabs, including both genuinely isolated and periodically repeated slabs with different terminations. The capability of dealing with a genuinely isolated slab is a virtue of the localized-basis implementation adopted here. We demonstrate, amongst other things, the nontrivial dynamical-charge neutrality of BaTiO 3 [001] surfaces.

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“…These modes are classified into three phonon bands which corresponds to normal modes of the ideal cubic perovskite: external modes (ω < 290 cm −1 ), bending mode at the intermediate range, and stretching modes (ω > 550 cm −1 ). The low frequency external modes are due to the vibrations of R and MnO 6 , while the intermediate frequency range bending modes and the high frequency stretching modes mainly involve vibrations of oxygen octahedra [20]. Hence, the modes assignment will be made by comparing the phonon frequencies obtained from the fit with those found in lattice dynamics calculations [17,24] as given in Table II.…”

Section: Resultsmentioning

confidence: 99%

Infrared Active Phonons and Optical Band Gap in Multiferroic GdMnO₃Studied by Infrared and UV-Visible Spectroscopy

Bukhari

Ahmad

2016

Acta Phys. Pol. A

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Optical properties of multiferroic GdMnO3 synthesized by sol-gel method have been investigated by measuring the infrared reflectivity and UV-visible absorption spectra. The infrared reflectivity spectrum of polycrystalline GdMnO3 in the frequency range 30-7500 cm −1 at room temperature contains several phonon modes. The resonant frequency of observed infrared active phonon modes is found comparable with theoretically predicted results. Mean Born effective charges are calculated and discussed in view of the origin of ferroelectricity in GdMnO3. Three strong absorption peaks observed in the UV-visible spectrum are attributed to the Mn (3d)-electron transitions. The optical band gap ≈ 1.2 eV is estimated from UV-visible absorption spectrum using Tauc's relation. GdMnO3 seems to behave like an indirect gap semiconductor.

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Infrared spectroscopy in KNbO₃through the successive ferroelectric phase transitions

Cited by 242 publications

References 39 publications

Semiempirical Hartree-Fock calculations forKNbO3

Semiempirical Hartree-Fock calculations forKNbO3

Hartree-Fock studies of the ferroelectric perovskites

Infrared Active Phonons and Optical Band Gap in Multiferroic GdMnO₃Studied by Infrared and UV-Visible Spectroscopy

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Infrared spectroscopy in KNbO3through the successive ferroelectric phase transitions

Cited by 242 publications

References 39 publications

Semiempirical Hartree-Fock calculations forKNbO3

Semiempirical Hartree-Fock calculations forKNbO3

Hartree-Fock studies of the ferroelectric perovskites

Infrared Active Phonons and Optical Band Gap in Multiferroic GdMnO3Studied by Infrared and UV-Visible Spectroscopy

Contact Info

Product

Resources

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Infrared spectroscopy in KNbO₃through the successive ferroelectric phase transitions

Infrared Active Phonons and Optical Band Gap in Multiferroic GdMnO₃Studied by Infrared and UV-Visible Spectroscopy