Octahedral tilting and ferroelectricity in Rb<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>A</mml:mi></mml:math>Nb<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow /><mml:mn>7</mml:mn></mml:msub></mml:math>(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>A</mml:mi></mml:math> = Bi, Nd) from first principles

Sim, Hyunsu; Kim, Bog G.

doi:10.1103/physrevb.89.144114

Cited by 36 publications

(64 citation statements)

References 45 publications

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“…The instability occurs at the R wave vector points and leads to the spontaneous decomposition of Pm3m Li 3 OCl into lower energy tilt systems, which has been observed in other perovskite materials 10,37 . Li 3 OCl is highly anharmonic with respect to rotational degrees of freedom of the Li 6 O octahedra.…”

Section: Discussionmentioning

confidence: 99%

Anharmonicity and phase stability of antiperovskiteLi3OCl

2015

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A lattice-dynamics study of the cubic Li3OCl anti-perovskite, a candidate solid electrolyte in lithium-ion batteries, reveals the presence of dynamical instabilities with respect to rotations of the Li6O octahedra. Calculated energy landscapes in the subspace of unstable octahedral rotational modes are very shallow with at most a 1 meV per formula unit reduction in energy upon breaking the cubic symmetry. While Li3OCl is not stable relative to decomposition into Li2O and LiCl at zero Kelvin, estimates of the vibrational free energy suggest that Li3OCl anti-perovskite should become entropically stabilized above approximately 480 K.

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Section: Discussionmentioning

confidence: 99%

Anharmonicity and phase stability of antiperovskiteLi3OCl

2015

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“…Experimental values at room temperature for the orthorhombic phase [40] are provided for comparison. [44,45]. The depth of the potential well has, for instance, been used as an indicator of the nature of the phase transitions, i.e., deep and shallow wells should correspond to order-disorder and displacive transitions, respectively.…”

Section: B Potential-energy Landscapesmentioning

confidence: 99%

Nature of the octahedral tilting phase transitions in perovskites: A case study of CaMnO3

Klarbring

Simak

2018

Phys. Rev. B

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The temperature-induced antiferrodistortive (AFD) structural phase transitions in CaMnO 3 , a typical perovskite oxide, are studied using first-principles density functional theory calculations. These transitions are caused by tilting of the MnO 6 octahedra that are related to unstable phonon modes in the high-symmetry cubic perovskite phase. Transitions due to octahedral tilting in perovskites normally are believed to fit into the standard soft-mode picture of displacive phase transitions. We calculate phonon-dispersion relations and potential-energy landscapes as functions of the unstable phonon modes and argue based on the results that the phase transitions are better described as being of order-disorder type. This means that the cubic phase emerges as a dynamical average when the system hops between local minima on the potential-energy surface. We then perform ab initio molecular dynamics simulations and find explicit evidence of the order-disorder dynamics in the system. Our conclusions are expected to be valid for other perovskite oxides, and we finally suggest how to predict the nature (displacive or order-disorder) of the AFD phase transitions in any perovskite system.

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“…The optical conductivity at 10 K shows a very narrow Drude peak with a minimum around 150 cm −1 . A phononic region with approximately ten infrared active modes is well noticeable in the 150-700 cm −1 frequency range [3]. By heating the sample the metallic contribution decreases in the farinfrared through a transfer of spectral weight (SW) to a mid-infrared (MIR) band centered around 1800 cm −1 .…”

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“…First theoretical insights about the mechanism behind the ferroelectric instability and the metallic character of LiOsO 3 were gained by using Density Functional Theory (DFT) calculations [3][4][5]. The ferroelectric transition in metallic LiOsO 3 mainly results from the cooperative displacements of Li and O ions, while the metallic conduction is associated with the t 2g orbitals of osmium which are partially occupied by three electrons per ion [4].…”

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Electronic correlations in the ferroelectric metallic state ofLiOsO3

et al. 2016

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LiOsO3 has been recently identified as the first unambiguous "ferroelectric metal", experimentally realizing a prediction from 1965 by Anderson and Blount. In this work, we investigate the metallic state in LiOsO3 by means of infrared spectroscopy supplemented by Density Functional Theory and Dynamical Mean Field Theory calculations. Our measurements and theoretical calculations clearly show that LiOsO3 is a very bad metal with a small quasiparticle weight, close to a Mott-Hubbard localization transition. The agreement between experiments and theory allows us to ascribe all the relevant features in the optical conductivity to strong electron-electron correlations within the t2g manifold of the osmium atoms. Introduction -Ferroelectric materials display a spontaneous polarization due to an inversion symmetry breaking induced by the macroscopic ordering of local dipole moments. Multiferroic materials are defined by coexistent and coupled magnetic and ferroelectric order. It is a natural expectation that ferroelectric (and consequently multiferroic) ordering can only happen in insulators in order to avoid the metallic charge carriers to screen out the ferroelectric polarization. The existence of "ferroelectric metals" challenging this expectation has been hypothesized in 1965 by Anderson and Blount [1], who have shown that ferroelectricity can occur in a metal as long as the electrons at the Fermi level are decoupled from the ferroelectric distortions. Under these circumstances, the ferroelectric ordering can take place through a second-order transition. In 2013 the first unambiguous realization of this proposal has been reported in LiOsO 3 , where a second-order transition leads to a ferroelectric ionic structure below 140 K while the material remains conducting [2]. This behavior is accompanied by a large residual resistivity which exceeds by two orders of magnitude that of prototypical metals as gold, and by a CurieWeiss like behavior of the magnetic susceptibility in the ordered phase which suggests the presence of almost localized magnetic moments, characteristic precursors of Mott localization [2].

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Octahedral tilting and ferroelectricity in RbANb2O7(A = Bi, Nd) from first principles

Cited by 36 publications

References 45 publications

Anharmonicity and phase stability of antiperovskiteLi3OCl

Anharmonicity and phase stability of antiperovskiteLi3OCl

Nature of the octahedral tilting phase transitions in perovskites: A case study of CaMnO3

Electronic correlations in the ferroelectric metallic state ofLiOsO3

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