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D Errandonea - One of the best experts on this subject based on the ideXlab platform.
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high Pressure Phase diagram and superionicity of alkaline earth metal difluorides
Journal of Physical Chemistry C, 2018Co-Authors: Claudio Cazorla, Arun K Sagotra, Meredith King, D ErrandoneaAbstract:We study the high-Pressure–high-temperature Phase diagram and superionicity of alkaline earth metal (AEM) difluorides (AF2, A = Ca, Sr, Ba) with first-principles simulation methods. We find that the superionic behavior of SrF2 and BaF2 at high Pressures differ appreciably from that previously reported for CaF2 [Phys. Rev. Lett. 2014, 113, 235902]. Specifically, the critical superionic temperature of SrF2 and BaF2 in the low-Pressure cubic fluorite Phase is not reduced by effect of compression, and the corresponding high-Pressure orthorhombic contunnite Phases become superionic at elevated temperatures. We get valuable microscopic insights into the superionic features of AEM difluorides in both the cubic fluorite and orthorhombic contunnite Phases by means of ab initio molecular dynamics simulations. We rationalize our findings on the structural and superionic behavior of AF2 compounds in terms of simple ionic radii arguments and generalize them across the whole series of AEM dihalides (AB2, A = Mg, Ca, Sr...
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high Pressure x ray diffraction study on the structure and Phase transitions of the defect stannite znga2se4 and defect chalcopyrite cdga2s4
arXiv: Materials Science, 2008Co-Authors: D Errandonea, Ravhi S Kumar, F J Manjon, V V Ursaki, I M TiginyanuAbstract:X-ray diffraction measurements on the sphalerite-derivatives ZnGa2Se4 and CdGa2S4 have been performed upon compression up to 23 GPa in a diamond-anvil cell. ZnGa2Se4 exhibits a defect tetragonal stannite-type structure (I-42m) up to 15.5 GPa and in the range from 15.5 GPa to 18.5 GPa the low-Pressure Phase coexists with a high-Pressure Phase, which remains stable up to 23 GPa. In CdGa2S4, we find the defect tetragonal chalcopyrite-type structure (I-4) is stable up to 17 GPa. Beyond this Pressure a Pressure-induced Phase transition takes place. In both materials, the high-Pressure Phase has been characterized as a defect-cubic NaCl-type structure (Fm-3m). The occurrence of the Pressure induced Phase transitions is apparently related with an increase of the cation disorder on the semiconductors investigated. In addition, the results allow the evaluation of the axial compressibility and the determination of the equation of state for each compound. The obtained results are compared with those previously reported for isomorphic digallium sellenides. Finally, a systematic study of the Pressure-induced Phase transition in twenty-three different sphalerite-related ABX2 and AB2X4 compounds indicates that the transition Pressure increases as the ratio of the cationic radii and anionic radii of the compounds increases.
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high Pressure x ray diffraction study on the structure and Phase transitions of the defect stannite znga2se4 and defect chalcopyrite cdga2s4
Journal of Applied Physics, 2008Co-Authors: D Errandonea, Ravhi S Kumar, F J Manjon, V V Ursaki, I M TiginyanuAbstract:X-ray diffraction measurements on the sphalerite-derivatives ZnGa2Se4 and CdGa2S4 have been performed upon compression up to 23 GPa in a diamond-anvil cell. ZnGa2Se4 exhibits a defect tetragonal stannite-type structure (I4¯2m) up to 15.5 GPa and in the range from 15.5 to 18.5 GPa the low-Pressure Phase coexists with a high-Pressure Phase, which remains stable up to 23 GPa. In CdGa2S4, we find that the defect tetragonal chalcopyrite-type structure (I4¯) is stable up to 17 GPa. Beyond this Pressure a Pressure-induced Phase transition takes place. In both materials, the high-Pressure Phase has been characterized as a defect-cubic NaCl-type structure (Fm3¯m). The occurrence of the Pressure-induced Phase transitions is apparently related with an increase in the cation disorder on the semiconductors investigated. In addition, the results allow the evaluation of the axial compressibility and the determination of the equation of state for each compound. The obtained results are compared to those previously report...
Valery I Levitas - One of the best experts on this subject based on the ideXlab platform.
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strain induced Phase transformation under compression in a diamond anvil cell simulations of a sample and gasket
Journal of Applied Physics, 2014Co-Authors: Biao Feng, Valery I LevitasAbstract:Combined high Pressure Phase transformations (PTs) and plastic flow in a sample within a gasket compressed in diamond anvil cell (DAC) are studied for the first time using finite element method. The key point is that Phase transformations are modelled as strain-induced, which involves a completely different kinetic description than for traditional Pressure-induced PTs. The model takes into account, contact sliding with Coulomb and plastic friction at the boundaries between the sample, gasket, and anvil. A comprehensive computational study of the effects of the kinetic parameter, ratio of the yield strengths of high and low-Pressure Phases and the gasket, sample radius, and initial thickness on the PTs and plastic flow is performed. A new sliding mechanism at the contact line between the sample, gasket, and anvil called extrusion-based pseudoslip is revealed, which plays an important part in producing high Pressure. Strain-controlled kinetics explains why experimentally determined Phase transformation Pressure and kinetics (concentration of high Pressure Phase vs. Pressure) differ for different geometries and properties of the gasket and the sample: they provide different plastic strain, which was not measured. Utilization of the gasket changes radial plastic flow toward the center of a sample, which leads to high quasi-homogeneous Pressure for some geometries. For transformation to a stronger high Pressure Phase, plastic strain and concentration of a high-Pressure Phase are also quasi-homogeneous. This allowed us to suggest a method of determining strain-controlled kinetics from experimentation, which is not possible for weaker and equal-strength high-Pressure Phases and cases without a gasket. Some experimental phenomena are reproduced and interpreted. Developed methods and obtained results represent essential progress toward the understanding of PTs under compression in the DAC. This will allow one optimal design of experiments and conditions for synthesis of new high Pressure Phases.
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modeling and simulation of strain induced Phase transformations under compression in a diamond anvil cell
Physical Review B, 2010Co-Authors: Valery I Levitas, Oleg M ZarechnyyAbstract:Strain-induced Phase transformations (PTs) under high-Pressure differ fundamentally from the Pressure-induced PTs under quasihydrostatic conditions. A model and finite-element approach to strain-induced PTs under compression and torsion of a sample in rotational diamond anvil cell are developed. The current paper is devoted to the numerical study of strain-induced PTs under compression in traditional diamond anvils while the accompanying paper [V. I. Levitas and O. M. Zarechnyy, Phys. Rev. B 82, 174124 (2010)] is concerned with compression and torsion in rotational anvils. Very heterogeneous fields of stress tensor, accumulated plastic strain, and concentration of the high-Pressure Phase are determined for three ratios of yield strengths of low-Pressure and high-Pressure Phases. PT kinetics depends drastically on the yield strengths ratios. For a stronger high-Pressure Phase, an increase in strength during PT increases Pressure and promotes PT, serving as a positive mechanochemical feedback; however, maximum Pressure in a sample is much larger than required for PT. For a weaker high-Pressure Phase, strong strain and high-Pressure Phase localization and irregular stress fields are obtained. Various experimentally observed effects are reproduced and interpreted. Obtained results revealed difficulties in experimental characterization of strain-induced PTs and suggested some ways to overcome them.
I M Tiginyanu - One of the best experts on this subject based on the ideXlab platform.
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high Pressure x ray diffraction study on the structure and Phase transitions of the defect stannite znga2se4 and defect chalcopyrite cdga2s4
arXiv: Materials Science, 2008Co-Authors: D Errandonea, Ravhi S Kumar, F J Manjon, V V Ursaki, I M TiginyanuAbstract:X-ray diffraction measurements on the sphalerite-derivatives ZnGa2Se4 and CdGa2S4 have been performed upon compression up to 23 GPa in a diamond-anvil cell. ZnGa2Se4 exhibits a defect tetragonal stannite-type structure (I-42m) up to 15.5 GPa and in the range from 15.5 GPa to 18.5 GPa the low-Pressure Phase coexists with a high-Pressure Phase, which remains stable up to 23 GPa. In CdGa2S4, we find the defect tetragonal chalcopyrite-type structure (I-4) is stable up to 17 GPa. Beyond this Pressure a Pressure-induced Phase transition takes place. In both materials, the high-Pressure Phase has been characterized as a defect-cubic NaCl-type structure (Fm-3m). The occurrence of the Pressure induced Phase transitions is apparently related with an increase of the cation disorder on the semiconductors investigated. In addition, the results allow the evaluation of the axial compressibility and the determination of the equation of state for each compound. The obtained results are compared with those previously reported for isomorphic digallium sellenides. Finally, a systematic study of the Pressure-induced Phase transition in twenty-three different sphalerite-related ABX2 and AB2X4 compounds indicates that the transition Pressure increases as the ratio of the cationic radii and anionic radii of the compounds increases.
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high Pressure x ray diffraction study on the structure and Phase transitions of the defect stannite znga2se4 and defect chalcopyrite cdga2s4
Journal of Applied Physics, 2008Co-Authors: D Errandonea, Ravhi S Kumar, F J Manjon, V V Ursaki, I M TiginyanuAbstract:X-ray diffraction measurements on the sphalerite-derivatives ZnGa2Se4 and CdGa2S4 have been performed upon compression up to 23 GPa in a diamond-anvil cell. ZnGa2Se4 exhibits a defect tetragonal stannite-type structure (I4¯2m) up to 15.5 GPa and in the range from 15.5 to 18.5 GPa the low-Pressure Phase coexists with a high-Pressure Phase, which remains stable up to 23 GPa. In CdGa2S4, we find that the defect tetragonal chalcopyrite-type structure (I4¯) is stable up to 17 GPa. Beyond this Pressure a Pressure-induced Phase transition takes place. In both materials, the high-Pressure Phase has been characterized as a defect-cubic NaCl-type structure (Fm3¯m). The occurrence of the Pressure-induced Phase transitions is apparently related with an increase in the cation disorder on the semiconductors investigated. In addition, the results allow the evaluation of the axial compressibility and the determination of the equation of state for each compound. The obtained results are compared to those previously report...
Joan F. Brennecke - One of the best experts on this subject based on the ideXlab platform.
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high Pressure Phase behavior of carbon dioxide with imidazolium based ionic liquids
Journal of Physical Chemistry B, 2004Co-Authors: Sudhir N V K Aki, Berlyn R Mellein, And Eric M Saurer, Joan F. BrenneckeAbstract:Previously we have shown that supercritical carbon dioxide can be used to extract organics from ionic liquids (ILs). Subsequently, ionic liquids/carbon dioxide biphasic solutions have been used for a variety of homogeneously catalyzed reactions. Therefore, an understanding of the Phase behavior of carbon dioxide with ionic liquids is needed to design extraction and reaction processes necessary for these applications. We present measurements of the solubility of carbon dioxide in 10 different imidazolium-based ionic liquids at 25, 40, and 60 °C and Pressures to 150 bar. As expected, the solubility increases with increasing Pressure and decreases with increasing temperature for all the ILs investigated. To investigate the influence of the anion, seven of the ILs studied have 1-butyl-3-methylimidazolium ([bmim]) as the cation. The anions are dicyanamide ([DCA]), nitrate ([NO3]), tetrafluoroborate ([BF4]), hexafluorophosphate ([PF6]), trifuoromethanesulfonate ([TfO]), bis(trifluoromethylsulfonyl)imide ([Tf2N]...
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high Pressure Phase behavior of ionic liquid co2 systems
Journal of Physical Chemistry B, 2001Co-Authors: Lynnette A Blanchard, Joan F. BrenneckeAbstract:This work presents the high-Pressure Phase behavior of CO2 with six ionic liquids: 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]), 1-n-octyl-3-methylimidazolium hexafluorophosphate ([C8-mim][PF6]), 1-n-octyl-3-methylimidazolium tetrafluoroborate ([C8-mim][BF4]), 1-n-butyl-3-methylimidazolium nitrate ([bmim][NO3]), 1-ethyl-3-methylimidazolium ethyl sulfate ([emim][EtSO4]), and N-butylpyridinium tetrafluoroborate ([N-bupy][BF4]). We explored the effect of systematically changing the anionic and cationic components of the ionic liquid on the CO2−ionic liquid Phase behavior. For all of the ionic liquids tested, large quantities of CO2 dissolved in the ionic liquid Phase, but no appreciable amount of ionic liquid solubilized in the CO2 Phase. In addition, the liquid Phase volume expansion with the introduction of even large amounts of CO2 is negligible, in dramatic contrast to the large volume expansion observed for neutral organic liquids. Our results seek to elucidate the underlying physica...
Robert A Heidemann - One of the best experts on this subject based on the ideXlab platform.
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high Pressure Phase equilibria in the systems linear low density polyethylene n hexane and linear low density polyethylene n hexane ethylene experimental results and modelling with the sanchez lacombe equation of state
Journal of Supercritical Fluids, 2006Co-Authors: I Nagy, Th W De Loos, Ryan A Krenz, Robert A HeidemannAbstract:Abstract Cloud point isopleths, bubble-point isopleths and liquid–liquid–vapour bubble point isopleths were measured for a binary system of linear low density polyethylene (LLDPE) and n-hexane and for the ternary system LLDPE + n-hexane + ethylene. The experiments were performed according to the synthetic method in the temperature range 400–500 K and at Pressures up to 14 MPa. The LLDPE used was a hydrogenated polybutadiene and was almost monodisperse (Mw/Mn = 1.19). Measured experimental data for the system LLDPE + n-hexane and experimental data for the system LLDPE + ethylene taken from literature [H. Trumpi, Th.W. de Loos, R.A. Krenz, R.A. Heidemann, High Pressure Phase equilibria in the system linear low density polyethylene + ethylene: experimental results and modeling, J. Supercrit. Fluids 27 (2003) 205–214.] were modelled with the modified Sanchez-Lacombe equation of state. The same LLDPE sample was used in both experiments. The parameters for LLDPE were found by performing a sequence of non-linear regressions on Pressure–volume–temperature reference data for molten polyethylene and the experimental cloud point data for the systems LLDPE + n-hexane and LLDPE + ethylene. From this information and a Sanchez-Lacombe fit to n-hexane + ethylene data the Phase behaviour of the ternary system LLDPE + n-hexane + ethylene can be predicted. Using this procedure the influence of the ethylene concentration on the cloud point Pressure is slightly under predicted. Therefore, the LLDPE–ethylene binary interaction parameter was adjusted to ternary LLDPE + hexane + ethylene cloud point data. In this way the modified Sanchez-Lacombe equation gives a very good description of the ternary cloud point curves and an almost quantitative prediction of the ternary bubble point and liquid–liquid–vapour boundary curves.
