The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform
Francesco Mauri - One of the best experts on this subject based on the ideXlab platform.
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Quantum Hydrogen-bond symmetrization in the superconducting Hydrogen sulfide system
Nature, 2016Co-Authors: Ion Errea, Joseph R. Nelson, Yunwei Zhang, Hanyu Liu, Yinwei Li, Matteo Calandra, Richard J. Needs, Chris J Pickard, Yanming Ma, Francesco MauriAbstract:The quantum nature of the proton can crucially affect the structural and physical properties of Hydrogen Compounds. For example, in the high-pressure phases of H2O, quantum proton fluctuations lead to symmetrization of the Hydrogen bond and reduce the boundary between asymmetric and symmetric structures in the phase diagram by 30 gigapascals (ref. 3). Here we show that an analogous quantum symmetrization occurs in the recently discovered sulfur hydride superconductor with a superconducting transition temperature Tc of 203 kelvin at 155 gigapascals-the highest Tc reported for any superconductor so far. Superconductivity occurs via the formation of a compound with chemical formula H3S (sulfur trihydride) with sulfur atoms arranged on a body-centred cubic lattice. If the Hydrogen atoms are treated as classical particles, then for pressures greater than about 175 gigapascals they are predicted to sit exactly halfway between two sulfur atoms in a structure with symmetry. At lower pressures, the Hydrogen atoms move to an off-centre position, forming a short H-S covalent bond and a longer H···S Hydrogen bond in a structure with R3m symmetry. X-ray diffraction experiments confirm the H3S stoichiometry and the sulfur lattice sites, but were unable to discriminate between the two phases. Ab initio density-functional-theory calculations show that quantum nuclear motion lowers the symmetrization pressure by 72 gigapascals for H3S and by 60 gigapascals for D3S. Consequently, we predict that the phase dominates the pressure range within which the high Tc was measured. The observed pressure dependence of Tc is accurately reproduced in our calculations for the phase, but not for the R3m phase. Therefore, the quantum nature of the proton fundamentally changes the superconducting phase diagram of H3S.
Ion Errea - One of the best experts on this subject based on the ideXlab platform.
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Quantum Hydrogen-bond symmetrization in the superconducting Hydrogen sulfide system
Nature, 2016Co-Authors: Ion Errea, Joseph R. Nelson, Yunwei Zhang, Hanyu Liu, Yinwei Li, Matteo Calandra, Richard J. Needs, Chris J Pickard, Yanming Ma, Francesco MauriAbstract:The quantum nature of the proton can crucially affect the structural and physical properties of Hydrogen Compounds. For example, in the high-pressure phases of H2O, quantum proton fluctuations lead to symmetrization of the Hydrogen bond and reduce the boundary between asymmetric and symmetric structures in the phase diagram by 30 gigapascals (ref. 3). Here we show that an analogous quantum symmetrization occurs in the recently discovered sulfur hydride superconductor with a superconducting transition temperature Tc of 203 kelvin at 155 gigapascals-the highest Tc reported for any superconductor so far. Superconductivity occurs via the formation of a compound with chemical formula H3S (sulfur trihydride) with sulfur atoms arranged on a body-centred cubic lattice. If the Hydrogen atoms are treated as classical particles, then for pressures greater than about 175 gigapascals they are predicted to sit exactly halfway between two sulfur atoms in a structure with symmetry. At lower pressures, the Hydrogen atoms move to an off-centre position, forming a short H-S covalent bond and a longer H···S Hydrogen bond in a structure with R3m symmetry. X-ray diffraction experiments confirm the H3S stoichiometry and the sulfur lattice sites, but were unable to discriminate between the two phases. Ab initio density-functional-theory calculations show that quantum nuclear motion lowers the symmetrization pressure by 72 gigapascals for H3S and by 60 gigapascals for D3S. Consequently, we predict that the phase dominates the pressure range within which the high Tc was measured. The observed pressure dependence of Tc is accurately reproduced in our calculations for the phase, but not for the R3m phase. Therefore, the quantum nature of the proton fundamentally changes the superconducting phase diagram of H3S.
Herbert C Brown - One of the best experts on this subject based on the ideXlab platform.
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reaction of sodium aluminum hydride with selected organic Compounds containing representative functional groups comparison of the reducing characteristics of lithium and sodium aluminum hydrides
Journal of Organic Chemistry, 1993Co-Authors: Herbert C BrownAbstract:The approximate rate and stoichiometry of the reaction of excess sodiumaluminum hydride (SAH) with organic Compounds containing representative functional groups under standardized conditions (tetrahydrofuran, 0 o C) were examined in order to define the reducing characteristics of the reagent and compare the reducing power with lithium aluminum hydride (LAH). In general, the reducing action and power of the reagent are similar to those of LAH. All of the active Hydrogen Compounds including alcohols, amines, and thiols evolve Hydrogen instantly. Aldehydes and ketones are reduced very rapidly and quantitatively to give the corresponding alcohols
Yinwei Li - One of the best experts on this subject based on the ideXlab platform.
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Quantum Hydrogen-bond symmetrization in the superconducting Hydrogen sulfide system
Nature, 2016Co-Authors: Ion Errea, Joseph R. Nelson, Yunwei Zhang, Hanyu Liu, Yinwei Li, Matteo Calandra, Richard J. Needs, Chris J Pickard, Yanming Ma, Francesco MauriAbstract:The quantum nature of the proton can crucially affect the structural and physical properties of Hydrogen Compounds. For example, in the high-pressure phases of H2O, quantum proton fluctuations lead to symmetrization of the Hydrogen bond and reduce the boundary between asymmetric and symmetric structures in the phase diagram by 30 gigapascals (ref. 3). Here we show that an analogous quantum symmetrization occurs in the recently discovered sulfur hydride superconductor with a superconducting transition temperature Tc of 203 kelvin at 155 gigapascals-the highest Tc reported for any superconductor so far. Superconductivity occurs via the formation of a compound with chemical formula H3S (sulfur trihydride) with sulfur atoms arranged on a body-centred cubic lattice. If the Hydrogen atoms are treated as classical particles, then for pressures greater than about 175 gigapascals they are predicted to sit exactly halfway between two sulfur atoms in a structure with symmetry. At lower pressures, the Hydrogen atoms move to an off-centre position, forming a short H-S covalent bond and a longer H···S Hydrogen bond in a structure with R3m symmetry. X-ray diffraction experiments confirm the H3S stoichiometry and the sulfur lattice sites, but were unable to discriminate between the two phases. Ab initio density-functional-theory calculations show that quantum nuclear motion lowers the symmetrization pressure by 72 gigapascals for H3S and by 60 gigapascals for D3S. Consequently, we predict that the phase dominates the pressure range within which the high Tc was measured. The observed pressure dependence of Tc is accurately reproduced in our calculations for the phase, but not for the R3m phase. Therefore, the quantum nature of the proton fundamentally changes the superconducting phase diagram of H3S.
Joseph R. Nelson - One of the best experts on this subject based on the ideXlab platform.
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Quantum Hydrogen-bond symmetrization in the superconducting Hydrogen sulfide system
Nature, 2016Co-Authors: Ion Errea, Joseph R. Nelson, Yunwei Zhang, Hanyu Liu, Yinwei Li, Matteo Calandra, Richard J. Needs, Chris J Pickard, Yanming Ma, Francesco MauriAbstract:The quantum nature of the proton can crucially affect the structural and physical properties of Hydrogen Compounds. For example, in the high-pressure phases of H2O, quantum proton fluctuations lead to symmetrization of the Hydrogen bond and reduce the boundary between asymmetric and symmetric structures in the phase diagram by 30 gigapascals (ref. 3). Here we show that an analogous quantum symmetrization occurs in the recently discovered sulfur hydride superconductor with a superconducting transition temperature Tc of 203 kelvin at 155 gigapascals-the highest Tc reported for any superconductor so far. Superconductivity occurs via the formation of a compound with chemical formula H3S (sulfur trihydride) with sulfur atoms arranged on a body-centred cubic lattice. If the Hydrogen atoms are treated as classical particles, then for pressures greater than about 175 gigapascals they are predicted to sit exactly halfway between two sulfur atoms in a structure with symmetry. At lower pressures, the Hydrogen atoms move to an off-centre position, forming a short H-S covalent bond and a longer H···S Hydrogen bond in a structure with R3m symmetry. X-ray diffraction experiments confirm the H3S stoichiometry and the sulfur lattice sites, but were unable to discriminate between the two phases. Ab initio density-functional-theory calculations show that quantum nuclear motion lowers the symmetrization pressure by 72 gigapascals for H3S and by 60 gigapascals for D3S. Consequently, we predict that the phase dominates the pressure range within which the high Tc was measured. The observed pressure dependence of Tc is accurately reproduced in our calculations for the phase, but not for the R3m phase. Therefore, the quantum nature of the proton fundamentally changes the superconducting phase diagram of H3S.
