Vibronic Theory of Structural Phase Transitions and Displacive Ferroelectrics

Kristoffel, N.; Konsin, P.

doi:10.1002/pssb.2221490102

Cited by 57 publications

(51 citation statements)

References 107 publications

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“…In contrast, in non-ferroelectrics, the strength of the el-TOph interaction is not necessarily high enough due to their lower polar nature. This result corresponds to the main assumption of the vibronic theory [12][13][14][15] regarding the existence of sufficiently strong interband el-TO-ph coupling in displacive ferroelectrics. The strength of the interband el-TO-ph interaction can therefore serve as a direct indicator of the extent to which a crystal lattice is close to a possible ferroelectric instability.…”

Section: Resultssupporting

confidence: 80%

“…The values of g j given in Table 1 for the wide-gap ferroelectrics can be compared with the only known semi-empirical estimate of Ref. [12] for BaTiO 3 , which, in turn, should be recast by applying the accurate magnitude of the effective charge: using the value 8.33 estimated from the data of Table 1, one obtains the corrected estimate 4.2 eV/Å, which is close to the value 4.7 eV/Å of Table 1 for BaTiO 3 .…”

Section: Resultsmentioning

confidence: 99%

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Evaluation of the electron–TO–phonon interaction in polar crystals from experimental data

Pishtshev

2010

Physica B: Condensed Matter

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The aim of this study was to determine the strengths of the coupling of electrons with the polar longwavelength transverse optical (TO) vibrations from infrared spectroscopy data. This determination is made by means of a simple relationship between the electron-TO-phonon interaction constant and material parameters, based on a parametrization of the electron-TO-phonon coupling in terms of the long-range dipole-dipole interaction. The combination of experimental data employed here allowed us to calculate directly the relevant constants for a number of representative polar insulators and to show that in ferroelectrics the interband electron-TO-phonon interaction at the Γ point is essentially strong. In these calculations, infrared spectroscopy methods proved to be an effective tool for study of the main properties of electron interaction with polar long-wavelength TO phonons.

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Section: Resultssupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Evaluation of the electron–TO–phonon interaction in polar crystals from experimental data

Pishtshev

2010

Physica B: Condensed Matter

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“…Generally, this interaction, as an ion-covalent system specific bonding component associated with the purely dynamic part of the charge transfer, is fundamental for the structural stability of polarized insulating crystals such as displacive ferroelectrics. [95][96][97][98] Because of the spatial non-uniformity inherent to the distribution of the electronic density in X − O − H, it is important to understand what kind of movements in this structure -changes in an ionic environment or distortions of electronic shells caused by mixing with long-wavelength optical vibrations -is principal in treating the macroscopic crystal polarizability and effects of the local field. In this context, analysis of the components of the tensor of the Born effective charges is of great importance because their enhanced values with respect to some reference (nominal) ionic values serve as confirmation for many-body electronic polarization effects that contribute to ionic dipole polarization.…”

Section: Mg(oh)mentioning

confidence: 99%

Materials properties of magnesium and calcium hydroxides from first-principles calculations

Pishtshev

Karazhanov

Klopov

2014

Computational Materials Science

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This work presents a study of ground state properties, electronic structure, dielectric and optical properties of magnesium and calcium hydroxides X(OH)2 (X = Mg and Ca) within PBE-GGA and range-separated hybrid functional schemes as well as by using GW approximation. The relevant HSE06 hybrid functional mixing parameters were determined from a self-consistent adjustment to the electronic dielectric constant ǫ∞. It was shown that the overall performance of our adaptation of the HSE06 functional via implementation of the modified amount of the Fock exchange is nearly best for the ground state properties as compared to other relevant HF and DFT methods. Structural stability of the crystalline X(OH)2 hydroxides has been considered in static and dynamic aspects. The most important factors describing the bonding situation have been investigated, and a crystalchemical integrity of the hydroxides has been analyzed. From electronic structure studies it was found that both materials are direct band gap insulators. Predictions for the fundamental band gaps were shown to be in the range of 7.7-8.3 eV for Mg(OH) 2 and 7.3-7.6 eV for Ca(OH) 2 . The origin of the conduction and valence band states near the band edges has been studied in terms of orbital and site projected density of states as well as by comparison with the X-ray photoelectron spectroscopy measurements. It was shown that effective masses of carriers at the Γ-point in vicinity of the band extreme are strongly anisotropic and for the electrons are similar to those in the ZnO crystal. Optical properties of the bulk X(OH)2 hydroxides have been investigated in terms of the real and imaginary parts of the optical dielectric function calculated in GW approximation. Electronic character of anisotropy of optical properties has been clarified. On the base of the obtained results the potential of applicability of the Mg(OH) 2 and Ca(OH) 2 crystalline hydroxides in semiconductor device engineering and optoelectronics has been analyzed.

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“…(Note that the electron-phonon coupling is responsible for the ferroelectric instability in the vibronic theory of ferroelectricity (Kristoffel and Konsin, 1988), i.e., the existence of the pseudo Jahn-Teller effect due to the existence of two closely situated filled p and d empty bands in perovskites-like structures (Sinha and Sinha, 1964)). …”

Section: G Electronically Driven Instabilitymentioning

confidence: 99%

The nature of ferroelectricity under pressure

Kornev

Bellaïche

2007

Phase Transitions

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Advances in first-principles computational approaches have, over the past fifteen years, made possible the investigation of physical properties of ferroelectric systems. In particular, such approaches have led to a microscopic understanding of the occurrence of ferroelectricity in perovskite oxides at ambient pressure. In this paper, we report ab-initio studies on the effect of hydrostatic pressure on the ferroelectricity in perovskites and related materials. We found that, unlike commonly believed, these materials exhibit ferroelectricity at high enough pressure. We also explained in details the (unusual) nature of this ferroelectricity.

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Vibronic Theory of Structural Phase Transitions and Displacive Ferroelectrics

Cited by 57 publications

References 107 publications

Evaluation of the electron–TO–phonon interaction in polar crystals from experimental data

Evaluation of the electron–TO–phonon interaction in polar crystals from experimental data

Materials properties of magnesium and calcium hydroxides from first-principles calculations

The nature of ferroelectricity under pressure

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