Ionic layered PbFCl-type compounds under high pressure

Decremps, F.; Fischer, Michael; Polian, A.; Itié, J. P.; Sieskind, M.

doi:10.1103/physrevb.59.4011

Cited by 48 publications

(35 citation statements)

References 29 publications

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“…The cause of the observed anisotropy has been correlated [7,9] to the electronic polarizability α X of the X anion (in Debye units, α Cl = 2.96, α Br = 4.16, α I = 6.43 [10]), which, and because of the asymmetric position of X inside the pyramid M 4+1 -X, creates electrical dipole moments on the anion. For the most layered compounds (e.g.…”

Section: The Mfx Matlockitesmentioning

confidence: 96%

“…Moreover, the anisotropy observed in these crystal being clearly connected to the large polarizability of X [7,9], the M 4+1 X linear compressibilities perpendicular (parallel) to the C 4 axis χ ⊥( ) (pyr) can be simply characterized by three parameters d M X , d M X and α X :…”

Section: Compressibility Of M 4+1 X Pyramidsmentioning

confidence: 99%

“…In the present work, we propose to adapt this model to bidimensional compounds in order to predict the structural behaviour of ionic layered crystals under high pressure. To validate the model, a calculation of the compressibilities of matlockite-type compounds is undertaken and compared with the experimental results obtained by different techniques like ultrasonics [3][4][5] or X-ray diffraction [6,7]. To complete the previous published data on the matlockite compressibilities, X-ray absorption spectroscopy under high pressure has been carried out on two compounds of this family, SrFCl and SrFBr, which allowed to determine the local compressibility of the Sr-F bonds in both compound.…”

Section: Introductionmentioning

confidence: 99%

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Prediction of cell variations with pressure of ionic layered crystal Application to the matlockite family

et al. 1999

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Compounds belonging to the matlockite family are ionic layered crystals. Some previous experimental studies on these compounds demonstrated the correlation between the difference in bond strength translating the layered properties and the anisotropic coordination of the highly polarizable halogen anion. In the present paper, we present a model to estimate the anisotropic compressibilities of matlockites which could be generalized to other ionic layered compounds. The compressibilities of each individual polyhedron which built the sheet of an ionic layered crystal are determined from a simple relation based on a semiempirical relation obtained by Hazen et al., involving the electrical charge of the ions and the interatomic distances. The electrical charge of the anions are taken to be direction-dependent and are modulated by the anion polarizability value. Finally, to validate the model, the calculated compressibilities are compared with previously published data, but also with new high pressure experimental data obtained by X-ray absorption spectroscopy up to 20 GPa on SrFCl and SrFBr at the K edge of the strontium and by X-ray diffraction up to 30 GPa on SrFBr and PbFBr. Present estimations give results which differ from the experimental values by less than 15%. PACS. 64.30.+t Equations of state of specific substances -62.20.-x Mechanical properties of solids -61.10.Ht X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.

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Section: The Mfx Matlockitesmentioning

confidence: 96%

Section: Compressibility Of M 4+1 X Pyramidsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Prediction of cell variations with pressure of ionic layered crystal Application to the matlockite family

et al. 1999

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“…Structural [1][2][3] and electronic [4] studies under high pressure up to 50 GPa have been experimentally carried out on the PbFCl-type crystals. In this rapid note we have examined the nature of the structural phase transitions in BaFCl under hydrostatic pressure up to 30 GPa by molecular dynamics (MD) simulations.…”

mentioning

confidence: 99%

“…The alkaline-earth fluorohalides when doped with divalent rare-earth ions, Sm 2þ , are currently used as a more sensitive pressure gauge [1] than the ruby sensor for high-pressure measurements in a diamond-anvil cell. Structural [1][2][3] and electronic [4] studies under high pressure up to 50 GPa have been experimentally carried out on the PbFCl-type crystals.…”

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confidence: 99%

Molecular Dynamics Simulations of the High-Pressure Phase Transitions in BaFCl

Liu

Kurobori

Hirose

2001

phys. stat. sol. (b)

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The alkaline-earth fluorohalides when doped with divalent rare-earth ions, Sm 2þ , are currently used as a more sensitive pressure gauge [1] than the ruby sensor for high-pressure measurements in a diamond-anvil cell. Structural [1][2][3] and electronic [4] studies under high pressure up to 50 GPa have been experimentally carried out on the PbFCl-type crystals. In this rapid note we have examined the nature of the structural phase transitions in BaFCl under hydrostatic pressure up to 30 GPa by molecular dynamics (MD) simulations.The system including 750 atoms in the computational cell was simulated under an isobaric-isothermal (N, T, P) ensemble, where N is the number of atoms, T the temperature and P the pressure. The time step was 1 fs and a cut-off distance was 10 A. The details of the calculations can be found elsewhere [5,6]. The following two cases of simulations were carried out as a function of pressure using the Born-Mayer-Huggins potential for the atomic interaction, in which the parameters for BaFCl are taken from the studies of Baetzold [7]:(sim1) At 300 K, the pressure was increased from 0.1 MPa to 30 GPa with a rate of 0.2 GPa/ps, and decreased from 30 GPa to 0.1 MPa with the same rate.(sim2) At 300 K, the pressure was increased instantaneously between 0.1 MPa and 30 GPa every 5 GPa. For example, in the case of 30 GPa, the rate was about 6 GPa/ps. Figure 1 shows the time dependence of the lattice parameters (a, b, g; a, b, c) and the volume V, when pressure P is varied with a rate of AE0.2 GPa/ps (sim1; see Fig. 1d). In our simulations, the structural changes suddenly occur at two different pressures. One can see the first-order phase transitions with crystallographic changes at about 28.92 GPa in the upstroke process and at about 18.04 GPa in the downstroke process. The simulated transition pressure, 28.92 GPa, is higher than the experimental value [2], 21 GPa, with a conventional diamond-anvil cell. The difference may be attributed to the ideal crystal used in our simulations without having vacancies and impurities. In Fig. 1a, at the first break in the upstroke process when the phase transition takes place, the angle a changes from 90 to 107 and then at the second break in the downstroke process the angle a changes further from 107 to 122 . Figure 1b shows that the magnitude along the unit-cell axes a and b is split into two lines at 28.92 GPa and then joined together at 18.04 GPa, while the unit-cell axis c shortens at 28.92 GPa and then c lengthens at 18.04 GPa abruptly. On the contrary, in the case of sim2, the behavior of the unit-cell axes, a, b and c, was similar as that of sim1, but the angle b changes from 90 to 72 at the first break and returns to the original angle at the second break after occurring a relaxation oscillation. Figures 2a and 2b show the ionic trajectories on the yz-plane in the case of sim1 at 29.00 GPa, just after the phase transition takes place at the first break and at 18.06 GPa, just after that at the second break, respectively. It was found that each atom in BaFCl ...

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Computational discovery of new modifications in scandium oxychloride (ScOCl) using a multi‐methodological approach

Zagorac¹,

Zagorac²,

Fonović

et al. 2022

Zeitschrift anorg allge chemie

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Dedicated to Professor Thomas Schleid on the occasion of his 65th birthdayScandium oxychloride (ScOCl) has recently become of interest as an advanced material with possible applications in solid oxide fuel cells, photocatalysis, and electronic devices, as are oxyhalides of various transition metals. In the present study, crystal structure prediction has been utilized to fully investigate the energy landscape of ScOCl. A multi-methodological approach has been used consisting of a combination of two search methods, where the final structure optimization has been performed on ab initio level using DFT-LDA and hybrid PBE0 functionals. The experimentally observed α-ScOCl phase has been found as well as several additional structure candidates at high pressures and/or temperatures. A successful synthesis of these novel ScOCl modifications would have the potential for extending the scientific, technological and industrial applications of ScOCl.

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Ionic layered PbFCl-type compounds under high pressure

Cited by 48 publications

References 29 publications

Prediction of cell variations with pressure of ionic layered crystal Application to the matlockite family

Prediction of cell variations with pressure of ionic layered crystal Application to the matlockite family

Molecular Dynamics Simulations of the High-Pressure Phase Transitions in BaFCl

Computational discovery of new modifications in scandium oxychloride (ScOCl) using a multi‐methodological approach

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