The role of oxygen vacancies on the vibrational motions of hydride ions in the oxyhydride of barium titanate

Eklöf-Österberg, Carin; Mazzei, Laura; Granhed, Erik Jedvik; Wahnström, Göran; Nedumkandathil, Reji; Häußermann, Ulrich; Jaworski, Aleksander; Pell, Andrew J.; Parker, Stewart F.; Jalarvo, Niina; Börjesson, Lars; Karlsson, Maths

doi:10.1039/c9ta11912d

Cited by 10 publications

(7 citation statements)

References 34 publications

(73 reference statements)

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“…This can be viewed as a confirmation of the impact of the R 25 mode. This mode is very easily populated as the temperature increases, due to its very low frequency [61]. The oxygen octahedra itself remains rigid.…”

Section: Mean-square Relative Displacementmentioning

confidence: 99%

BaZrO3 stability under pressure: The role of nonlocal exchange and correlation

2020

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The ground-state structure of BaZrO 3 is experimentally known to be cubic down to absolute zero. However, there exist several measured properties and experimental characterizations that earlier computational works have failed to accurately describe and explain within this cubic symmetry. Among these properties and observations are the dielectric constant and the parallel mean-squared relative displacement value that tracks the fluctuations in distance for Ba-O atom pairs. Previous density-functional theory (DFT) studies have resolved the issue by assuming that BaZrO 3 undergoes a phase transition from cubic to tetragonal I4/mcm symmetry, possibly while forming a glasslike state that reflects cubic symmetry on average. In this paper, we show that the set of experimental results can indeed be satisfactorily explained by DFT entirely within the cubic symmetry. We find that past theory limitations arose from the choice of exchange-correlation-functional approximations and that the inclusion of Fock exchange in hybrids significantly improves the DFT performance. We also find that the inclusion of nonlocal correlation effects is beneficial. We conclude by making a prediction for the phase-transition pressure for the transition from cubic to tetragonal symmetry at zero kelvin.

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Section: Mean-square Relative Displacementmentioning

confidence: 99%

BaZrO3 stability under pressure: The role of nonlocal exchange and correlation

2020

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“…The quantification results reveal that BTOD NAB has a lower hydride concentration than samples reduced with CaH 2 , which is in agreement with previous studies. 17,24 The hydride shifts are tabulated in Table 1, along with the determined hydride content y. We notice that the shift becomes more negative with increasing hydride concentration, which is the first indication that the examined materials are in a bandstate.…”

Section: Comparison Of 1 H and 2 H Solid-state Nmrmentioning

confidence: 87%

“…Possibly, this ion arrangement dominates within the oxyhydride structure, therefore hydride ion diffusion occurs exclusively via the next-nearest-neighbour hopping mechanism. 17…”

Section: Hydride Conduction Dynamicsmentioning

confidence: 99%

“…In the second mechanism hydride ions move through the material with the assistance of oxygen vacancies. Several investigations using complementary methods, such as isotope exchange, 5 quantum chemical calculations, 15 quasielastic neutron scattering (QENS) 16 and inelastic neutron scattering (INS) 17 have indicated that the latter mechanism most likely occurs in BaTiO 3Àx H y oxyhydride and other ATiO 3Àx H y pervoskites. 18,19 While the majority of the studies are in agreement on the general hydride ion transport mechanism, they differ on important details regarding the hydride ion hopping distance (nearest or next-nearest oxygen vacancy) and the dynamic process time scale.…”

Section: Introductionmentioning

confidence: 99%

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Probing the electronic structure and hydride occupancy in barium titanium oxyhydride through DFT-assisted solid-state NMR

Aleksis

Nedumkandathil

Papawassiliou

et al. 2022

Phys. Chem. Chem. Phys.

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“…In the second mechanism hydride ions move through the material with the assistance of oxygen vacancies. Several investigations using complementary methods, such as isotope exchange, 5 quantum chemical calculations 15 , quasielastic neutron scattering (QENS) 16 and inelastic neutron scattering (INS) 17 have indicated that the latter mechanism most likely occurs in BaTiO 3 x H y oxyhydride and other ATiO 3 x H y pervoskites. 18,19 While the majority of the studies are in agreement on the hydride ion transport mechanism in these solids, controversies still remain on the electronic structure and the associated electrical conductivity.…”

Section: Introductionmentioning

confidence: 99%

Probing the electronic structure and hydride occupancy in barium titanium oxyhydride through DFT-assisted solid-state NMR

Aleksis

Nedumkandathil

Papawassiliou

et al. 2022

Preprint

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Perovskite-type oxhydrides such as BaTiO3−xHy exhibit mixed hydride ion and electron conduction and are an attractive class of materials for developing energy storage devices. However, the underlying mechanism of electric conductivity and its relation to the composition of the material remains unclear. Here we report detailed insights into the hydride local environment, the electronic structure and hydride conduction dynamics of barium titanium oxyhydride. We demonstrate that DFT-assisted solid-state NMR is an excellent tool for differentiating between the different feasible electronic structures in these solids. Our results indicate that upon reduction of BaTiO3 the introduced electrons are delocalized among all Ti atoms forming a bandstate. Furthermore, each vacated anion site is reoccupied by at most a single hydride, or else remains vacant. This single occupied bandstate structure persists at different hydrogen concentrations (y = 0.13−0.31) and a wide range of temperatures (∼ 100−300 K).

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The role of oxygen vacancies on the vibrational motions of hydride ions in the oxyhydride of barium titanate

Abstract: Combined INS and DFT study on BaTiO3−xHx unravels the effect of oxygen vacancies on the vibrational dynamics of hydride ions.

Cited by 10 publications

References 34 publications

BaZrO3 stability under pressure: The role of nonlocal exchange and correlation

BaZrO3 stability under pressure: The role of nonlocal exchange and correlation

Probing the electronic structure and hydride occupancy in barium titanium oxyhydride through DFT-assisted solid-state NMR

Probing the electronic structure and hydride occupancy in barium titanium oxyhydride through DFT-assisted solid-state NMR

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