Structural, electronic and optical properties of cubic SrTiO3 and KTaO3: Ab initio and GW calculations

Benrekia, Ahmed Redha; Benkhettou, N.; Nassour, Ayoub; Driz, M.; Sahnoun, M.; Lebègue, Sébastien

doi:10.1016/j.physb.2012.04.013

Cited by 66 publications

(30 citation statements)

References 37 publications

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“…a. By comparing with GW calculations , one can find that the energy‐loss spectra for both cases are consistent with each other for KTaO 3 at the corresponding regions. In Fig.…”

Section: Resultssupporting

confidence: 70%

“…In addition, the positions of the relevant peaks of imaginary part curves also exhibit some slight deviations due to the different calculation methods. Taking KTaO 3 as an example, Sinha et al [32] reported four peaks at 5.8, 6.6, 10.1, and 11.4 eV with GGA and correction technique, and 5.1, 7.3, 11.7, and 13.8 eV with the GW [41] and 5.64, 7.78, 12.06, and 14.73 eV with the present HSE06, respectively. Thus, the present results are closer to those with GW [41] for KTaO 3 , which also indicates the validity of the present calculations.…”

Section: Optical Propertiesmentioning

confidence: 85%

“…7a Using GGA calculations, Okoye [33] provided the real and imaginary part curves of KNbO 3 in the range 0-20 eV, and Sinha et al [32] presented the imaginary part curves in the range 0-12 eV for KNbO 3 and KTaO 3 . Cabuk et al [34] and Benrekia et al [41] showed the real and imaginary part curves of KTaO 3 with LDA and GW calculations in the ranges 0-25 and 0-35 eV, respectively. In essence, the shapes of the present curves are substantially consistent with [34] are slightly different from the other curves in shape.…”

Section: Optical Propertiesmentioning

confidence: 99%

See 2 more Smart Citations

First‐principles study of structural, electronic, elastic, and optical properties of cubic KNbO₃ and KTaO₃ crystals

Zhang

et al. 2016

Physica Status Solidi (b)

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Cubic KNbO3 and KTaO3 crystals are studied using the first‐principles VASP code. By employing local density approximation (LDA), GGA‐PBE, and HSE06, the lattice parameters are optimized and compared with available experimental data, and the best agreement is achieved with HSE06. Electronic structures such as density of states, band structures, and charge‐density distribution are discussed in detail for both crystals. The single‐crystal elastic constants, polycrystalline elastic modulus, compressibility, Poisson's ratio, and anisotropy factors are obtained from the Voigt–Reuss–Hill approximation. The elastic anisotropy is modeled and visualized in the light of the elastic properties of both systems. The bandgaps of the two crystals are calculated with LDA, PBE, HSE06, and GW approximations (GW0), and the results of HSE06 and GW0 agree well with experimental data. Then the more reliable optical properties of KNbO3 and KTaO3 are acquired based on the bandgaps with HSE06, in which the previous scissors operator correction is avoided. Both crystals are brittle, and KTaO3 exhibits higher hardness and stiffness than KNbO3. Some novel results, such as Debye temperatures, sound velocities, and the extreme values of Young's modulus are obtained.

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“…a. By comparing with GW calculations , one can find that the energy‐loss spectra for both cases are consistent with each other for KTaO 3 at the corresponding regions. In Fig.…”

Section: Resultssupporting

confidence: 70%

Section: Optical Propertiesmentioning

confidence: 85%

Section: Optical Propertiesmentioning

confidence: 99%

See 1 more Smart Citation

First‐principles study of structural, electronic, elastic, and optical properties of cubic KNbO₃ and KTaO₃ crystals

Zhang

et al. 2016

Physica Status Solidi (b)

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“…As a matter of fact, the band edge states of anatase TiO 2 (Fig. 5) and SrTiO 3 45, 46 are parallel in extended portions of the BZ, which contribute density of states to the collective transition associated with bound excitonic species ( E B ~180/220 meV) 11, 47 . In contrast, the band structure of rutile TiO 2 is not characterised by such extended portions with similar electron and hole group velocities 11 , thus resulting in E B ~4 meV 43, 44 .…”

Section: Discussionmentioning

confidence: 99%

Strongly bound excitons in anatase TiO2 single crystals and nanoparticles

et al. 2017

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Anatase TiO2 is among the most studied materials for light-energy conversion applications, but the nature of its fundamental charge excitations is still unknown. Yet it is crucial to establish whether light absorption creates uncorrelated electron–hole pairs or bound excitons and, in the latter case, to determine their character. Here, by combining steady-state angle-resolved photoemission spectroscopy and spectroscopic ellipsometry with state-of-the-art ab initio calculations, we demonstrate that the direct optical gap of single crystals is dominated by a strongly bound exciton rising over the continuum of indirect interband transitions. This exciton possesses an intermediate character between the Wannier–Mott and Frenkel regimes and displays a peculiar two-dimensional wavefunction in the three-dimensional lattice. The nature of the higher-energy excitations is also identified. The universal validity of our results is confirmed up to room temperature by observing the same elementary excitations in defect-rich samples (doped single crystals and nanoparticles) via ultrafast two-dimensional deep-ultraviolet spectroscopy.

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“…Its relatively high dielectric constant and its low dissipation factor in the microwave range in particular make KTO per of particular interest for tunable microwave devices 4. This cubic perovskite structure ( Pm $\bar 3$ m ) has K at the corners, Ta at the center, and O at the face centers, and can be viewed as TaO 6 octahedra with K in the large central sites between them 5. The refined lattice parameter a is 3.9885 Å 6…”

Section: Introductionmentioning

confidence: 99%

Pyrochlore and Perovskite Potassium Tantalate: Enthalpies of Formation and Phase Transformation

Złotnik

Sahu

Navrotsky

et al. 2015

Chemistry A European J

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Alkali niobates and tantalates are currently important lead-free functional oxides. The formation and decomposition energetics of potassium tantalum oxide compounds (K2 O-Ta2 O5 ) were measured by high-temperature oxide melt solution calorimetry. The enthalpies of formation from oxides of KTaO3 perovskite and defect pyrochlores with K/Ta ratio of less than 1 stoichiometry-K0.873 Ta2.226 O6 , K1.128 Ta2.175 O6 , and K1.291 Ta2.142 O6 -were experimentally determined, and the values are (-203.63 ± 2.92) kJ mol(-1) for KTaO3 perovskite, and (-339.54 ± 5.03) kJ mol(-1) , (-369.71 ± 4.84) kJ mol(-1) , and (-364.78 ± 4.24) kJ mol(-1) , respectively, for non-stoichiometric pyrochlores. That of stoichiometric defect K2 Ta2 O6 pyrochlore, by extrapolation, is (-409.87 ± 6.89) kJ mol(-1) . Thus, the enthalpy of the stoichiometric pyrochlore and perovskite at K/Ta=1 stoichiometry are equal in energy within experimental error. By providing data on the thermodynamic stability of each phase, this work supplies knowledge on the phase-formation process and phase stability within the K2 O-Ta2 O5 system, thus assisting in the synthesis of materials with reproducible properties based on controlled processing. Additionally, the relation of stoichiometric and non-stoichiometric pyrochlore with perovskite structure in potassium tantalum oxide system is discussed.

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Structural, electronic and optical properties of cubic SrTiO3 and KTaO3: Ab initio and GW calculations

Cited by 66 publications

References 37 publications

First‐principles study of structural, electronic, elastic, and optical properties of cubic KNbO₃ and KTaO₃ crystals

First‐principles study of structural, electronic, elastic, and optical properties of cubic KNbO₃ and KTaO₃ crystals

Strongly bound excitons in anatase TiO2 single crystals and nanoparticles

Pyrochlore and Perovskite Potassium Tantalate: Enthalpies of Formation and Phase Transformation

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Structural, electronic and optical properties of cubic SrTiO3 and KTaO3: Ab initio and GW calculations

Cited by 66 publications

References 37 publications

First‐principles study of structural, electronic, elastic, and optical properties of cubic KNbO3 and KTaO3 crystals

First‐principles study of structural, electronic, elastic, and optical properties of cubic KNbO3 and KTaO3 crystals

Strongly bound excitons in anatase TiO2 single crystals and nanoparticles

Pyrochlore and Perovskite Potassium Tantalate: Enthalpies of Formation and Phase Transformation

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First‐principles study of structural, electronic, elastic, and optical properties of cubic KNbO₃ and KTaO₃ crystals

First‐principles study of structural, electronic, elastic, and optical properties of cubic KNbO₃ and KTaO₃ crystals