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196 results on '"Rachdi F"'

1. 23Na and 13C NMR investigation of Na2C60 and Na6C60 fullerides

Author

Rachdi F.

Subjects
Physics, QC1-999
Abstract

We report on 23Na and 13C NMR measurements on Na2C60 and Na6C60 compounds. The 23Na NMR spectrum of A2C60 shows one line at 73 ppm and the one of A6C60 presents two lines at 73 and 147 ppm. The intensity ratio of the latter lines is about 2:1. According topreviously reported x-ray data we attribute the line at 147 ppm to the Na tetramers in the octahedral sites and the line at 73 ppm to the Na cations in the tetrahedral ones which are singly occupied. The room-temperature 13C NMR spectra of Na2C60 and Na6C60 samples present a narrow isotropic line at 172 and 176 ppm, respectively. The Na6C60 resonance is shifted 20 ppm more down field than the resonances of A6C60 compounds with heavier alkalis, indicating a partial charge transfer to the threefold degenerate t1u level which is totally filled in the latter compounds.

Published
2012
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2. NMR Studies of Fullerene C60-Based Compounds

Author

Bernier, P., Rachdi, F., Ribet, M., Reichenbach, J., Firlej, L., Lambert, J. M., Zahab, A., Belahmer, Z., Aznar, R., Cardona, Manuel, editor, Fulde, Peter, editor, von Klitzing, Klaus, editor, Queisser, Hans-Joachim, editor, Lotsch, Helmut K. V., editor, Kuzmany, Hans, editor, Fink, Jörg, editor, Mehring, Michael, editor, and Roth, Siegmar, editor

Published
1993
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3. NMR on Alkali-Doped C60

Author

Zimmer, G., Helmle, M., Mehring, M., Rachdi, F., Reichenbach, J., Firlej, L., Bernier, P., Cardona, Manuel, editor, Fulde, Peter, editor, von Klitzing, Klaus, editor, Queisser, Hans-Joachim, editor, Lotsch, Helmut K. V., editor, Kuzmany, Hans, editor, Fink, Jörg, editor, Mehring, Michael, editor, and Roth, Siegmar, editor

Published
1993
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19. Which aggregate complexity is required for an accurate computation off stress and plastic strain fields?

Author

Sauzay, M., Liu, J., Rachdi, F., Signor, L., Ghidossi, T., Villechaise, P., CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Université Pierre et Marie Curie - Paris 6 (UPMC), Institut Pprime (PPRIME), Université de Poitiers-ENSMA-Centre National de la Recherche Scientifique (CNRS), and amplexor, amplexor

Subjects
[PHYS.NUCL] Physics [physics]/Nuclear Theory [nucl-th], FE method, [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th], [PHYS.NEXP] Physics [physics]/Nuclear Experiment [nucl-ex], Crystal Plasticity, mean-field homogeneisation, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Multiscale Modeling
Abstract

International audience; The increasing efficiency of computations allows the numerical evaluation of stress and plastic strain fields in aggregates which description is finer and finer. Either the FE metof or the FFT method may be used. During the two last decades, such numerical computations lead to many new results, for instance allowing the validation of mean field homogeneisation schemes.

Published
2015

20. High-resolution 13C nuclear magnetic resonance in alkali intercalated fullerene C60.

Author

Reichenbach, J., Rachdi, F., Luk’yanchuk, I., Ribet, M., Zimmer, G., and Mehring, M.

Subjects
*NUCLEAR magnetic resonance spectroscopy, *POTASSIUM, *RUBIDIUM, *MOLECULAR dynamics
Abstract

We present the results of 13C nuclear magnetic resonance (NMR) measurements on potassium and rubidium doped Buckminster fullerene C60 at room temperature. By using high-resolution magic angle spinning NMR spectroscopy we were able to identify and characterize the different, thermodynamically stable phases. Based on an analysis of the different NMR spectra, we discuss the effects of the intercalation on the molecular dynamics as well as on the electronic properties in these compounds. [ABSTRACT FROM AUTHOR]

Published
1994
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22. 13C high resolution nuclear magnetic resonance studies in polycrystalline tetracyanoquinodimethane.

Author

Nunes, T., Vainrub, A., Ribet, M., Rachdi, F., Bernier, P., and Almeida, M.

Subjects
NUCLEAR magnetic resonance, POLYCRYSTALS, CYANIDES
Abstract

13C high resolution NMR (nuclear magnetic resonance) studies of solid neutral tetracyanoquinodimethane are performed using different polycrystalline samples: (i) natural isotopic abundance; (ii) 15N isotope enriched; (iii) 13C isotope selectively enriched on the CN groups; and (iv) 13C isotope selectively enriched on the first neighboring carbons of the CN groups. 14N quadrupole effects are observed on 13C spectra of the CN groups, and the quadrupole coupling constant for 14N is obtained: -3.84±0.12 MHz. The 13C isotropic chemical shifts are found: 112.6 ppm for CN groups; 90.8 ppm for the carbons directly bonded to these groups; 132.0 and 133.2 ppm for protonated carbons; and 151.7 ppm for the other carbons on the quinone ring. The principal components of the chemical shielding tensor, the shielding anisotropy, and the shielding asymmetry factor are also obtained for the 13C nuclei in the fragments C–(CN)2, by graphical analysis of CP/MAS spectra. The following values are obtained for 13C nuclei on CN groups: 211±11 ppm, -85±22 ppm (σ⊥ and σ||); -296±33 ppm (Δσ), and 0 (η). For the other carbon nuclei the values obtained for σ11, σ22, σ33, Δσ, and η are: 157±2 ppm, 75±2 ppm, 39±3 ppm, -77±4 ppm and 1.6±0.1, respectively. The reliability of these results is confirmed by a computer fit of the line intensities. [ABSTRACT FROM AUTHOR]

Published
1992
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25. In situ pressure study of Rb4C60 insulator to metal transition by Compton scattering

Author

Sabouri-Dodaran, A.A., Bellin, Ch., Loupias, G., Marangolo, Massimiliano, Rabii, S., Rachdi, F., Buslaps, Th., Mezouar, M., Institute for Studies in Theoretical Physics and Mathematics, Payame Noor University, Institut de minéralogie et de physique des milieux condensés (IMPMC), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Institut des Nanosciences de Paris (INSP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Department of Electrical and Systems Engineering, University of Pennsylvania, Groupe de Dynamique des Phases Condensées (GDPC), Université Montpellier 2 - Sciences et Techniques (UM2)-Centre National de la Recherche Scientifique (CNRS), European Synchrotron Radiation Facility (ESRF), Université Pierre et Marie Curie - Paris 6 (UPMC)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), University of Pennsylvania [Philadelphia], and Centre National de la Recherche Scientifique (CNRS)-Université Montpellier 2 - Sciences et Techniques (UM2)

Subjects
rubidium compounds, Compton effect, ab initio calculations, band structure, fullerene compounds, metal-insulator transition, electronic density of states, ground states
Abstract

Compton scattering has been shown to be a powerful tool for studying the ground state electronic density in real materials. Using synchrotron radiation, we have studied pressure effects on Rb4C60 by measuring the Compton profiles below and above the insulator to metal transition at 0.8 GPa. The experimental results are compared with the corresponding calculated results, obtained from new ab initio energy band structure calculations. These results allow us to quantitatively evaluate contributions to the Compton profiles resulting from the contraction of the unit cell as well as from the contraction of the C60 molecule itself. In this paper, we point out an unexpected contraction of the volume of the C60 molecule, leading to a major effect on the electronic density of the Rb4C60 compound.

Published
2005
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26. Equations of state of RbxC60 (x=3,4 and 6)

Author

A. Sabouri-Dodaran., A., Marangolo, Massimiliano, Bellin., Ch., Mauri, Francesco, Fiquet ., G., Loupias., G., Mezouar., M., Crichton., W., Hérold., C., Rachdi., F., Rabii, S., Laboratoire de minéralogie, cristallographie de Paris (LMCP), Université Pierre et Marie Curie - Paris 6 (UPMC)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)

Subjects
high-pressure solid-state phase transformations, rubidium compounds, equations of state, 61.48.+c, 61.50.Ks, 71.20.Tx, ab initio calculations, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], compressibility, fullerene compounds, metal-insulator transition, X-ray diffraction
Abstract

The equations of state (EOS) of RbxC60 (x = 3, 4, and 6) were determined by high pressure x-ray diffraction measurements. We focus on Rb4C60 since a Mott insulator-metal transition can be induced at around 0.8 GPa. We observed an abrupt jump in the compressibility of Rb4C60 between 0.5 GPa and 0.8 GPa which is attributed to a structural phase transition preserving the tetragonal symmetry. By ab initio calculations we are able to reproduce the experimental equations of state of RbxC60 (x = 3,4). These calculations permit us to study the pressure dependence of the internal coordinates.

Published
2004
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29. 129Xe NMR Study of Small Sodium Particles in NaY Zeolite

Author

Trescos, Eric, De Menorval, Louis-Charles, Rachdi, F., Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Groupe de Dynamique des Phases Condensées (GDPC), and Centre National de la Recherche Scientifique (CNRS)-Université Montpellier 2 - Sciences et Techniques (UM2)

Subjects
Xe-129 NMR, Nay zeolite, Sodium Particles, [CHIM.MATE]Chemical Sciences/Material chemistry
Abstract

International audience; The distribution of sodium metal particles inside the cavities of a NaY zeolite has been investigated using 129Xe NMR spectroscopy. For a sample prepared by vapor-phase deposition at 520 K, the 129Xe NMR spectrum shows three lines which are interpreted in terms of domains of a nonuniformly distributed metal particles, oxidized particles, and empty cavities. After annealing the sample at 670 K, the lz9Xe spectrum collapses to one single line, characteristic of a narrow particle size distribution. Oxidation of the sample by oxygen decreases the chemical shift of the 129Xe NMR line, which is mainly due to a loss of paramagnetism and a volume contraction of the small sodium metal particles.

Published
1993
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32. Equations of state ofRbxC60(x=3, 4, and 6)

Author

Sabouri-Dodaran, A. A., primary, Marangolo, M., additional, Bellin, Ch., additional, Mauri, F., additional, Fiquet, G., additional, Loupias, G., additional, Mezouar, M., additional, Crichton, W., additional, Hérold, C., additional, Rachdi, F., additional, and Rabii, S., additional

Published
2004
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34. 23Na and 13C NMR investigation of Na2C60 and Na6C60 fullerides.

Author

Rachdi, F.

Subjects
SPECTRUM analysis, NUCLEAR magnetic resonance, ION exchange (Chemistry), CHARGE transfer, ELECTRONS
Abstract

We report on 23Na and 13C NMR measurements on Na2C60 and Na6C60 compounds. The 23Na NMR spectrum of A2C60 shows one line at 73 ppm and the one of A6C60 presents two lines at 73 and 147 ppm. The intensity ratio of the latter lines is about 2:1. According topreviously reported x-ray data we attribute the line at 147 ppm to the Na tetramers in the octahedral sites and the line at 73 ppm to the Na cations in the tetrahedral ones which are singly occupied. The room-temperature 13C NMR spectra of Na2C60 and Na6C60 samples present a narrow isotropic line at 172 and 176 ppm, respectively. The Na6C60 resonance is shifted 20 ppm more down field than the resonances of A6C60 compounds with heavier alkalis, indicating a partial charge transfer to the threefold degenerate t1u level which is totally filled in the latter compounds. [ABSTRACT FROM AUTHOR]

Published
2012
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