First principles studies of the born effective charges and electronic dielectric tensors for the relaxor PMN (PbMg1/3Nb2/3O3)

Choudhury, N.; Cohen, R. E.

doi:10.1016/j.commatsci.2005.12.038

Cited by 11 publications

(4 citation statements)

References 19 publications

(47 reference statements)

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“…We find that Born effective charge is quite sensitive to ion positions and crystal symmetry since the effective charge for a particular ion varies significantly in B1a1 and I 4/mmm structures and the three O ions have different charges in the same phase. This observation is in agreement with a previous study by Choudhury et al [50] on PbMg 1/3 Nb 2/3 O 3 .…”

Section: Born Effective Charges (Becs)supporting

confidence: 94%

First-principles calculations of Born effective charges and spontaneous polarization of ferroelectric bismuth titanate

Roy

Prasad

Auluck

et al. 2010

J. Phys.: Condens. Matter

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In this study, we present the results of our first-principles calculations of the band structure, density of states and the Born effective charge tensors for the ferroelectric (ground state B1a1) and paraelectric (I4/mmm) phases of bismuth titanate. The calculations are done using the generalized gradient approximation (GGA) as well as the local density approximation (LDA) of the density functional theory. In contrast to the literature, our calculations on B1a1 structure using GGA and LDA yield smaller indirect band gaps as compared to the direct band gaps, in agreement with the experimental data. The density of states shows considerable hybridization among Ti 3d, Bi 6p and O 2p states indicating covalent nature of the bonds leading to the ferroelectric instability. The Born effective charge tensors of the constituent ions for the ground state (B1a1) and paraelectric (I4/mmm) structures were calculated using the Berry phase method. This is followed by the calculation of the spontaneous polarization for the ferroelectric B1a1 phase using the Born effective charge tensors of the individual ions. The calculated value for the spontaneous polarization of ferroelectric bismuth titanate using different Born effective charges was found to be in the range of 55±13 µC/cm 2 in comparison to the reported experimental value of (50±10 μC/cm 2 ) for single crystals. The origin of ferroelectricity is attributed to the relatively large displacements of those oxygen ions in the TiO 6 octahedra that lie along the a-axis of the bismuth titanate crystal. 77.22.Ej, 85.50.Gk, 71.15.Mb 3 PACS Number (s):

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Section: Born Effective Charges (Becs)supporting

confidence: 94%

First-principles calculations of Born effective charges and spontaneous polarization of ferroelectric bismuth titanate

Roy

Prasad

Auluck

et al. 2010

J. Phys.: Condens. Matter

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“…This choice is suggested in the work of other researchers. [2][3][4][5]18 Geometry optimization was first carried out by using the Broyden-Fletcher-Goldfarb-Shannon ͑BFGS͒ scheme and USP methods to obtain a stable ferroelectric structure. After the optimization, electric, and optical properties were calculated by using the NCP methods.…”

Section: Methodsmentioning

confidence: 99%

“…More recently, there has been a flurry of activities to theoretically study the effect of the ordered microregions. [1][2][3][4][5][6][7] Potassium tantalite niobate ͑KTa 1−x Nb x O 3 ͒, which is the solid solution of KNbO 3 and KTaO 3 , is important for many applications, including electro-optics, holography, and second harmonic generation. 8,9 KTa 1−x Nb x O 3 crystals are ferroelectric materials that display both displacivelike and orderdisorder-like properties.…”

Section: Introductionmentioning

confidence: 99%

Structural, electronic, and optical properties of ferroelectric KTa1/2Nb1/2O3 solid solutions

Shen

Zhou

2008

Journal of Applied Physics

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The first principles calculations within generalized gradient approximation have been used to determine the structural, electronic, and optical properties of three chemically ordered ferroelectric KTa1/2Nb1/2O3 phases, with B site cations ordered along the [100], [110], and [111] directions. Stable ferroelectric ground states are found in all structures. The energy bands, density of states, complex dielectric function, reflectivity, refractive index, extinction coefficient, optical conductivity, absorption coefficient, and energy loss function are calculated by using the stable ferroelectric structures. The calculated results show good agreement with the available experimental and theoretical data. It is found that the ferroelectric states are particularly sensitive to the chemical ordering of B site cations and the long-range ordering has significant effect on the properties of KTa1/2Nb1/2O3 crystals.

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“…The Born transverse effective charges, defined as: In ferroelectrics, the effective charges are often much larger than their nominal values, contrary to chemical intuition that they would be lower than their nominal charges due to cova-lency, as would be static Mulliken charges, for example. Tables 1 and 2 show computed effective charges for PbTiO 3 [8] and rhombohedrally ordered PMN [54]. The effective charges can be greatly enhanced, so that Z * for oxygen can reach values of above X!…”

Section: Perovskite Ferroelectricsmentioning

confidence: 99%

First-Principles Theories of Piezoelectric Materials

Cohen

2008

Piezoelectricity

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Piezoelectrics have long been studied using parameterized models fit to experimental data, starting with the work of Devonshire in 1954.[1] Much has been learned using such approaches, but they can also miss major phenomena if the materials properties are not well understood, as is exemplified by the realization that low-symmetry monoclinic phases are common around morphotropic phase boundaries, which was missed completed by low-order Devonshire models, and can only appear in higher order models.[2] In the last 15 years, a new approach has developed using first-principles computations, based on fundamental physics, with no essential experimental input other than the desired chemistry (nuclear charges). First-principles theory laid the framework for a basic understanding of the origins of ferroelectric behavior [3-7] and piezoelectric properties. [8][9][10][11] The range of properties accessible to theory continues to expand as does the accuracy of the predictions. We are moving towards the ability to design materials of desired properties computationally. Here we review some of the fundamental developments of our understanding of piezoelectric material behavior and ability to predict a wide range of properties using theoretical methods. This is not meant as a review of the literature. Comprehensive reviews of the literature of theoretical studies of ferroelectrics are given by Resta [12] and Rabe and Ghosez. [13]

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First principles studies of the born effective charges and electronic dielectric tensors for the relaxor PMN (PbMg1/3Nb2/3O3)

Cited by 11 publications

References 19 publications

First-principles calculations of Born effective charges and spontaneous polarization of ferroelectric bismuth titanate

First-principles calculations of Born effective charges and spontaneous polarization of ferroelectric bismuth titanate

Structural, electronic, and optical properties of ferroelectric KTa1/2Nb1/2O3 solid solutions

First-Principles Theories of Piezoelectric Materials

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