Crystal Structure of Mixed-Valence Gold Compound, Cs2AuIAuIIICl6 up to 18GPa.

Matsushita, Nobuyuki; Ahsbahs, H.; Hafner, S. S.; Kojima, Naoya

doi:10.4131/jshpreview.7.329

Cited by 11 publications

(8 citation statements)

References 15 publications

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“…b In the case of Cs 2 Au I Au III Cl 6 , a relation between computed EOS for both phases predicts a pressure-induced phase transition of ∼11.4 GPa that agrees with the measured 12 GPa (cf. Figure S1).…”

Section: Resultssupporting

confidence: 88%

“…The data points are represented by black circles, the red line is the profile (LeBail) fit. The pXRD analysis of all tested samples confirms the tetragonal structure of dicesium gold chloride as reported in refs and . All the diffraction peaks correspond to the tetragonal I 4 /mmm (no.…”

Section: Resultssupporting

confidence: 84%

“…The values of a and c do not change significantly in the series and are in good agreement with the reported literature. 37,39 An interesting feature is a preferential orientation effect observed for some of the samples. For a powderized sample with unoriented grains, the expected intensity ratio I(220)/I(112) is 0.34, whereas the observed I(220)/I(112) reaches 0.95 for Cs 2 Au 2 Cl 6 _1 and 2 for Cs 2 Au 2 Cl 6 _2.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Integrated Experimental and Theoretical Approach for Efficient Design and Synthesis of Gold-Based Double Halide Perovskites

et al. 2020

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Applied cutting-edge electronic structure and phonon simulations provide a reliable knowledge about the stability of perovskite structures and their electronic properties, which are crucial for design of effective nanomaterials. Gold is one of the exceptional elements, which can exist both as a monovalent and a trivalent ion in the B site of a double perovskite such as A2BIBIIIX6. However, until now, electronic properties of Cs2AuIAuIIIX6 have not been sufficiently explored and this material was never synthesized using Au1+ and Au3+ precursors in the preparation route. Here, computational simulations combined with an experimental study provide new insight into the properties and synthesis route of Cs2AuIAuIIIX6 (X = Cl, Br, and I) perovskites. First-principles calculations reveal that tetragonal Cs2AuIAuIIIX6 (X = I, Br, Cl) molecules present a band gap of 1.10, 1.15, and 1.40 eV, respectively. Application of novel approaches in the simulations of the VB-XPS for Cs2AuIAuIIICl6 allows replication of the observed spectrum and provides strong evidence of the reliability of the obtained results for the other perovskites Cs2AuIAuIIIX6, X = Br, I. Following theoretical findings, a one-step preparation route of the Cs2AuIAuIIICl6 is developed using a combination of monovalent and trivalent gold precursors at a relatively low temperature. It should be emphasized that this is the first synthesis of this material at low temperatures, allowing for obtaining highly crystalline Cs2Au2Cl6 particles with controlled morphology and without gold impurities. The band gap of synthesized Cs2AuIAuIIICl6 is extended into the NIR spectral range, where most other double perovskites are limited to higher energies, limiting their usage in single junction solar cells or in photocatalysis. The as-synthesized Cs2AuIAuIIICl6 exhibits high efficiency in a photocatalytic toluene degradation reaction under visible light irradiation. The developed approach provides information necessary for structure manipulation at the early stage of its synthesis and offers a new and useful guidance for design of novel improved lead-free inorganic halide perovskite with interesting optical and photocatalytic properties.

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Section: Resultssupporting

confidence: 88%

Section: Resultssupporting

confidence: 84%

Section: ■ Results and Discussionmentioning

confidence: 99%

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Integrated Experimental and Theoretical Approach for Efficient Design and Synthesis of Gold-Based Double Halide Perovskites

et al. 2020

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“… a ARTEMIS program, S 0 2 = 0.84, AuCs 2 Cl 6 was accepted as initial model structure . Experimental spectra fits were performed in k -space if not indicated otherwise. b MSmultiple scattering, Au–Cl1–Au–Cl2. …”

Section: Resultsmentioning

confidence: 99%

Gold Transport in Hydrothermal Chloride-Bearing Fluids: Insights from in Situ X-ray Absorption Spectroscopy and ab Initio Molecular Dynamics

Тагиров

Trigub

Filimonova

et al. 2018

ACS Earth Space Chem.

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Chloride-bearing fluids are widespread in the Earth’s interior from low-temperature subsurface conditions to deep lithosphere. The concentration of chloride salts varies from diluted aqueous solutions to concentrated brines and anhydrous (dry) chloride melts beneath volcanoes. Here we report an investigation of the state of Au in hydrothermal chloride fluids and anhydrous melts by means of in situ X-ray absorption spectroscopy combined with ab initio molecular dynamics simulations and thermodynamic modeling. The experiments included registration of Au L3-edge X-ray absorption near edge structure/extended X-ray absorption fine structure spectra of Au-bearing fluids in the temperature range from 350 to 575 °C at pressures of 150–4500 bar. Spectra of Au dissolved in dry CsCl/NaCl/KCl + K2S2O8 melt were recorded at 650 °C. It was found that Au is coordinated by two Cl atoms (R Au–Cl = 2.25–2.28 Å). The alkali metal atoms (Me) were detected in the distant coordination sphere of Au at R Au‑Me = 3.3–4.1 Å. The alkali metal cations in the vicinity of Au–Cl complex partly compensate the positive charge located on Au and, by this way, affect the Au–Cl distance. An increase of the fluid pressure causes expansion of the second coordination sphere composed of the alkali metal cations, which leads to the increase of the positive Au charge and results in slight contraction of the first coordination sphere of Au. Accordingly, the transport of Au in high-temperature chloride-bearing natural ore-forming fluids of moderate to high densities (>0.3 g·cm–3) can be explicitly described by the formation of the AuCl2 – at any salt concentration from low-salinity fluids to hydrosaline liquids and anhydrous melts. In general, this means that the hydrothermal fluid chemistry simplifies with increasing temperature.

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“…RbTlCl 3 , have very recently been discussed as new potential hosts for non-trivial electronic properties [9,10]. The structurally and electronically related compounds CsAuX 3 with X = Cl, Br, and I crystallize in the space group I 4/mmm in a distorted variation of the perovskite structure [11][12][13]. The gold atoms in CsAuX 3 are mixed valent with Au(I) and Au(III) centers, which occupy two different crystallographic sites at ambient conditions [14,15].…”

Section: Introductionmentioning

confidence: 99%

Large resistivity reduction in mixed-valent CsAuBr3 under pressure

Naumov

Huangfu

et al. 2019

Phys. Rev. B

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We report on high-pressure p ≤ 45 GPa resistivity measurements on the perovskite-related mixedvalent compound CsAuBr 3 . The compounds high-pressure resistivity can be classified into three regions: For low pressures (p < 10 GPa) an insulator to metal transition is observed; between p = 10 GPa and 14 GPa the room temperature resistivity goes through a minimum and increases again; above p = 14 GPa a semiconducting state is observed. From this pressure up to the highest pressure of p = 45 GPa reached in this experiment, the room-temperature resistivity remains nearly constant. We find an extremely large resistivity reduction between ambient pressure and 10 GPa by more than 6 orders of magnitude. This decrease is among the largest reported changes in the resistivity for this narrow pressure regime. We show -by an analysis of the electronic band structure evolution of this material -that the large change in resistivity under pressure in not caused by a crossing of the bands at the Fermi level. We find that it instead stems from two bands that are pinned at the Fermi level and that are moving towards one another as a consequence of the mixed-valent to single-valent transition. This mechanism appears to be especially effective for the rapid buildup of the density of states at the Fermi level. arXiv:1909.06874v1 [cond-mat.mtrl-sci]

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Crystal Structure of Mixed-Valence Gold Compound, Cs2AuIAuIIICl6 up to 18GPa.

Cited by 11 publications

References 15 publications

Integrated Experimental and Theoretical Approach for Efficient Design and Synthesis of Gold-Based Double Halide Perovskites

Integrated Experimental and Theoretical Approach for Efficient Design and Synthesis of Gold-Based Double Halide Perovskites

Gold Transport in Hydrothermal Chloride-Bearing Fluids: Insights from in Situ X-ray Absorption Spectroscopy and ab Initio Molecular Dynamics

Large resistivity reduction in mixed-valent CsAuBr3 under pressure

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