Nuclear dynamics in the metastable phase of the solid acid caesium hydrogen sulfate

Krzystyniak, M.; Drużbicki, Kacper; Fernandez-Alonso, Félix

doi:10.1039/c5cp05636e

Cited by 32 publications

(28 citation statements)

References 84 publications

(139 reference statements)

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“…As evidenced by figure 12, the relative error of the Gaussian fits of the heavy masses in the backscattering regime, measured as the ratio of the single-standard deviation (1-STD) of the fitted peak width to this peak width value, is of the order of 7% or better. As expected, the values of the widths are greater for larger nuclear masses and increase with increasing temperature in an almost monotonic manner, thus reflecting the Boltzmann population of partial vibrational densities of states contributing to respective peak Doppler broadening, a situation commonly occurring in the case of heavyweight nuclear species in condensed matter systems [29,30,46,57,63,78,79].…”

Section: Neutron Compton Scattering 331 Framework Bzcy72 Atomssupporting

confidence: 66%

Nuclear dynamics in BaZr_0.7Ce_0.2Y_0.1O_3−δ proton conductor as observed by neutron diffraction and Compton scattering

et al. 2020

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Concurrent neutron Compton scattering (NCS) and neutron diffraction experiments at temperatures between 70 K and 300 K have been performed on proton-conducting hydrated BaZr 0.7 Ce 0.2 Y 0.1 O 3−δ (BZCY72) fabricated by spark plasma sintering. A combined neutron data analysis, augmented with density functional theory modelling of lattice dynamics, has enabled, for the first time, a mass-selective appraisal of the combined thermal and nuclear quantum effect on nuclear dynamics and thermodynamic stability of this technologically important proton conducting perovskite oxide. The analysis suggests that the nuclear dynamics in hydrated BZCY72 is a result of a subtle interplay of harmonic, anharmonic and thermal effects, with the increased anharmonic character of the lattice dynamics above the orthorhombic to rhombohedral phase transition at 85 K. The anharmonic effect seems to be most pronounced in the case of oxygen and cerium. The analysis of the proton momentum distribution reveals that the concentration of the hydrogen in the BZCY72 lattice is constant across the orthorhombic to rhombohedral phase transition and further down to the room temperature. Moreover, the average hydrogen concentration obtained from our analysis of the mass-resolved neutron Compton scattering data seems to be commensurate with the total vacancy concentration in the BZCY72 framework. The calculation of the vibrational enthalpy of both phases allows obtaining the value of the enthalpy of the orthorhombic to the rhombohedral phase transition of −3.1±1 kJ mol −1 . Finally, our analysis of the nuclear kinetic energy of the proton obtained from NCS and the oxygen-oxygen distance distributions obtained from ND allows to conclude that BZCY72 in both the orthorhombic and rhombohedral phase at 70 K and 100 K respectively falls into the category of the KDP-type crystals where proton is probably under the influence of a double-well potential and forms hydrogen bonds of moderate strength. The obtained results have important ramifications for this technological important material. ( ) ·· · Materials most commonly used are solid-state solutions of Y-doped BaCeO 3 and BaZrO 3 [8-11]. Both endmembers exhibit outstanding protonic conductivities up to 10 -2 S cm −1 at 450°C [12].between chemical stability and easy fabrication, respectively offered by the end-members, special interest is taken in the composition BaZr 0.7 Ce 0.2 Y 0.1 O 3−δ (BZCY72) [6,13].In perovskite-type proton conductors, protons are not a part of the oxide lattice nor their stoichiometry. Instead, they are present as hydroxide defects, also known as protonic defects which they form together with oxide ions in equilibrium with an ambient stable hydrogen carrier. In most cases, water vapour is absorbed by the surface and dissociates into a hydroxide ion, which fills an oxygen vacancy, while the remaining proton forms a covalent bond with the surface oxygen [14][15][16].The crystal structure of BZCY72 has been precisely worked out by Mather et al employing combined highresolution neutron ...

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Section: Neutron Compton Scattering 331 Framework Bzcy72 Atomssupporting

confidence: 66%

Nuclear dynamics in BaZr_0.7Ce_0.2Y_0.1O_3−δ proton conductor as observed by neutron diffraction and Compton scattering

et al. 2020

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“…For both phases, all real modes are found across the entire Brillouin zone, consistent with mechanically stable materials. Phase III has been the subject of a comprehensive spectroscopic and computational investigation by Krzystyniak et al [28]. Our INS spectrum is of higher quality as it was recorded with a later generation of the instrument, otherwise both the observed and calculated (for the same choice of functional) spectra agree with the previous work [28].…”

Section: Cshso 4 Spectroscopysupporting

confidence: 59%

“…The vibrational spectroscopy of CsHSO 4 has been studied by infrared, Raman [12,[19][20][21][22][23][24][25] and inelastic neutron scattering [26][27][28] (INS) spectroscopies as a function of both pressure and temperature. Clear differences between the phases are readily apparent using infrared and Raman spectroscopies.…”

Section: Introductionmentioning

confidence: 99%

Structure and Dynamics of the Superprotonic Conductor Caesium Hydrogen Sulfate, CsHSO4

2020

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We have investigated caesium hydrogen sulfate, CsHSO4, in all three of its ambient pressure phases by total scattering neutron diffraction, inelastic neutron scattering (INS) and Raman spectroscopies and periodic density functional theory calculations. Above 140 °C, CsHSO4 undergoes a phase transition to a superprotonic conductor that has potential application in intermediate temperature fuel cells. Total scattering neutron diffraction data clearly show that all the existing structures of this phase are unable to describe the local structure, because they have either partial occupancies of the atoms and/or non-physical O–H distances. Knowledge of the local structure is crucial because it is this that determines the conduction mechanism. Starting from one of the previous models, we have generated a new structure that has no partial occupancies and reasonable O–H distances. After geometry optimisation, the calculated radial distribution function is in reasonable agreement with the experimental data, as are the calculated and observed INS and Raman spectra. This work is particularly notable in that we have measured INS spectra in the O–H stretch region above room temperature, which is extremely rare. The INS spectra have the enormous advantage that the electrical anharmonicity that complicates the infrared spectra is absent and the stretch modes are plainly seen.

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“…This approximation amounts to performing separate phonon calculations for a set of structures that reproduce the thermal expansion of the material [91]. In this spirit, the solid-acid CsHSO 4 has been studied in some detail recently using DINS and INS [92]. This material is a superb proton conductor above ca.…”

Section: Application To Crystalline Materialsmentioning

confidence: 99%

Electron-volt neutron spectroscopy: beyond fundamental systems

Andreani

Krzystyniak

Romanelli

et al. 2017

Advances in Physics

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141

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This work provides an up-to-date account of the use of electron-volt neutron spectroscopy in materials research. This is a growing area of neutron science, capitalising upon the unique insights provided by epithermal neutrons on the behaviour and properties of an increasing number of complex materials. As such, the present work builds upon the aims and scope of a previous contribution to this journal back in 2005, whose primary focus was on a detailed description of the theoretical foundations of the technique and their application to fundamental systems [see Andreani et al., Adv. Phys. 54 (2005) p.377] A lot has happened since then, and this review intends to capture such progress in the field. With both expert and novice in mind, we start by presenting the general principles underpinning the technique and discuss recent conceptual and methodological developments. We emphasise the increasing use of the technique as a non-invasive spectroscopic probe with intrinsic mass selectivity, as well as the concurrent use of neutron diffraction and first-principles computational materials modelling to guide and interpret experiments. To illustrate the state of the art, we discuss in detail a number of recent exemplars, chosen to highlight the use of electron-volt neutron spectroscopy across physics, chemistry, biology, and materials science. These include: hydrides and proton conductors for energy applications; protons, deuterons, and oxygen atoms in bulk water; aqueous protons confined in nanoporous silicas, carbon nanotubes, and graphene-related materials; hydrated water in proteins and DNA; and the uptake of molecular hydrogen by soft nanostructured media, promising materials for energy-storage applications. For the primary benefit of the novice, this last case study is presented in a pedagogical and question-driven fashion, in the hope that it will stimulate further work into uncharted territory by newcomers to the field. All along, we emphasise the increasing (and much-needed) synergy between experiments using electron-volt neutrons and contemporary condensed matter theory and materials modelling to compute and ultimately understand neutron-scattering observables, as well as their relation to materials properties not amenable to scrutiny using other experimental probes

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Nuclear dynamics in the metastable phase of the solid acid caesium hydrogen sulfate

Cited by 32 publications

References 84 publications

Nuclear dynamics in BaZr_0.7Ce_0.2Y_0.1O_3−δ proton conductor as observed by neutron diffraction and Compton scattering

Nuclear dynamics in BaZr_0.7Ce_0.2Y_0.1O_3−δ proton conductor as observed by neutron diffraction and Compton scattering

Structure and Dynamics of the Superprotonic Conductor Caesium Hydrogen Sulfate, CsHSO4

Electron-volt neutron spectroscopy: beyond fundamental systems

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Nuclear dynamics in the metastable phase of the solid acid caesium hydrogen sulfate

Cited by 32 publications

References 84 publications

Nuclear dynamics in BaZr0.7Ce0.2Y0.1O3−δ proton conductor as observed by neutron diffraction and Compton scattering

Nuclear dynamics in BaZr0.7Ce0.2Y0.1O3−δ proton conductor as observed by neutron diffraction and Compton scattering

Structure and Dynamics of the Superprotonic Conductor Caesium Hydrogen Sulfate, CsHSO4

Electron-volt neutron spectroscopy: beyond fundamental systems

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Product

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Nuclear dynamics in BaZr_0.7Ce_0.2Y_0.1O_3−δ proton conductor as observed by neutron diffraction and Compton scattering

Nuclear dynamics in BaZr_0.7Ce_0.2Y_0.1O_3−δ proton conductor as observed by neutron diffraction and Compton scattering