Nature of the octahedral tilting phase transitions in perovskites: A case study of 
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Klarbring, Johan; Simak, Sergei I.

doi:10.1103/physrevb.97.024108

Cited by 43 publications

(26 citation statements)

References 57 publications

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“…However, such assumption may be invalid for PZO, as the AFE transition have been advocated to possess a strong order-disorder character, as evidenced by (i) the existence of central mode 13,14 and (ii) the fact that disordered Pb displacement and oxygen tiltings were found to occur even in the cubic phase 15,16 . Interestingly, this picture of dynamic disorder in the cubic phase is similar to the recent studies of the AFD transitions in CaMnO 3 and inorganic halide perovskites 17,18 , where low-energy paths between local minima are found to be critical for understanding the finite-temperature transitions.…”

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confidence: 82%

Order-disorder transition in the prototypical antiferroelectric PbZrO3

Hellman

Bellaïche

2019

Phys. Rev. B

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The prototypical antiferroelectric PbZrO3 has several unsettled questions, such as the nature of the antiferroelectric transition, possible intermediate phase and the microscopic origin of the Pbam ground state. Using first principles, we show that no phonon becomes truly soft at the cubic-to-Pbam transition temperature, and the order-disorder character of this transition is clearly demonstrated based on molecular dynamics simulations and potential energy surfaces. The out-ofphase octahedral tilting is an important degree of freedom, which can collaborate with other phonon distortions and form a complex energy landscape with multiple minima. Candidates of the possible intermediate phase are suggested based on the calculated kinetic barriers between energy minima, and the development of a first-principles-based effective Hamiltonian. The use of this latter scheme further reveals that specific bi-linear interactions between local dipoles and octahedral tiltings play a major role in the formation of the Pbam ground state, which contrasts with most of the previous explanations.Antiferroelectrics (AFEs) form a special class of materials that possess anti-polar displacements, which was first conceptualized by Kittel 1 . AFEs have received much attention in recent years because they hold great potential to reach high energy density for high-power energy storage 2-4 . Lead zirconate PbZrO 3 (PZO) is the first discovered AFE material, and crystallizes in a Pbam ground state below ∼505 K 5-7 . Besides the anti-polar distortions, this particular structure also exhibits strong longranged order tiltings of oxygen octahedra, which is often termed as antiferrodistortive (AFD) distortions.Despite the efforts devoted to understanding the origin of the AFE ground state in PZO 8-10 , how distortions condense from the high-symmetry cubic structure remains an open issue. Unlike proper ferroelectrics where the ferroelectric (FE) distortion results from soft polar mode in the cubic phase, it is presently unclear if PZO is a proper AFE. As a matter of fact, on one hand, completely soft AFE and AFD modes have been predicted at the AFE transition temperature (T A ) by Fthenakis et al. based on an effective Hamiltonian method 11 . On the other hand, no truly soft AFE or AFD modes was observed in Ref. 8 . In this regards, Tagantsev et al. proposed that the AFE transition in PZO is driven by a non-critical softening of the transverse acoustic mode via flexoelectric coupling 8 ; however, this mechanism is rather exotic and has recently been ruled out 12 . Moreover, from an energetic point of view,Íñiguez et al.. believe that the AFD mode plays a crucial role and PZO may be an improper AFE 9 .In fact, the above considerations in Refs. 9,11 rely on the existence of a displacive transition, for which the distortions in the antiferroelecrtic state are derived from sudden deviations from the ideal cubic structure at T A . However, such assumption may be invalid for PZO, as the AFE transition have been advocated to possess a strong order-disorder c...

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confidence: 82%

Order-disorder transition in the prototypical antiferroelectric PbZrO3

Hellman

Bellaïche

2019

Phys. Rev. B

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“…Strong anharmonic vibrations could also play a role in stabilizing these metastable phases. 51 A thorough mapping of potential hopping barriers between local minima in the potential energy surface is left for future study.…”

Section: A Structure and Stabilitymentioning

confidence: 99%

Property control from polyhedral connectivity in ABO3 oxides

2019

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We investigate the effect of the degree of metal-oxygen octahedral facesharing on the mechanical and electronic properties of d 0 BaTiO3 and d 3 BaMnO3. We find that increased facesharing softens the elastic constants of both materials due to the increased volume per atom, with polar distortions also contributing to the reduction in the bulk modulus. Owing to orbital filling in the d manifold, we find the electronic band gap of BaTiO3 is relatively unaffected by changes in percent facesharing whereas the band gap of BaMnO3 increases by more than 200 % as the percent facesharing increases from 0 % (cubic perovskite) to 100 % (hexagonal BaNiO3 perovskite). We identify that the trigonal distortions present in the face-connected polymorphs represent useful atomistic structural knobs to tune band structure in hexagonal perovskites. Our results indicate that facesharing hexagonal polymorphs provide an expanded oxides arena with additional structural flexibility beyond the usual fully-corner-connected perovskites for property control.

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“…Recently, there has been increasing evidence that the high temperature cubic phase of many perovskites is not, in fact, cubic on a local scale [12][13][14][15][16][17]. Instead, the cubic phase emerge as a result of static and/or dynamic disorder.…”

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confidence: 99%

Low-energy paths for octahedral tilting in inorganic halide perovskites

Klarbring

2019

Phys. Rev. B

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Instabilities relating to cooperative octahedral tilting is common in materials with perovskite structures, and in particular in the sub class of halide perovskites. In this work, the energetics of octahedral tilting in the inorganic metal halide perovskites CsPbI3 and CsSnI3 are investigated using first-principles density functional theory calculations. Several low energy paths between symmetry equivalent variants of the stable orthorhombic (Pnma) perovskite variant are identified and investigated. The results are in favor of the presence of dynamic disorder in the octahedral tilting phase transitions of inorganic halide perovskites. In particular, one specific type of path, corresponding to an out-of-phase "tilt switch", is found to have significantly lower energy barrier than the others, which indicates the existence of a temperature range where the dynamic fluctuations of the octahedra follow only this type of path. This could produce a time averaged structure corresponding to the intermediate tetragonal (P4/mbm) structure observed in experiments. Deficiencies of the commonly employed simple one-dimensional "double well" potentials in describing the dynamics of the octahedra are pointed out and discussed. arXiv:1802.09632v3 [cond-mat.mtrl-sci]

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

Cited by 43 publications

References 57 publications

Order-disorder transition in the prototypical antiferroelectric PbZrO3

Order-disorder transition in the prototypical antiferroelectric PbZrO3

Property control from polyhedral connectivity in ABO3 oxides

Low-energy paths for octahedral tilting in inorganic halide perovskites

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