Mason P.E.,Czech Institute of Organic Chemistry And Biochemistry |
Neilson G.W.,University of Bristol |
Price D.L.,Conditions Extremes et Materiaux Haute Temperature et Irradiation |
Saboungi M.-L.,CNRS Center for Research on Divided Matter |
Brady J.W.,Cornell University
Faraday Discussions | Year: 2013
The method of intramolecular coordination number concentration invariance (ICNCI) is used on neutron diffraction with isotopic substitution (NDIS) measurements of aqueous solutions to separate the intra- and intermolecular contributions to the total intensities. Molecular dynamics simulations of corresponding systems are then used to interpret the ICNCI function. It is found that the ICNCI function (characterized by two concentration measurements) is sensitive specifically to intermolecular association and that the molecular dynamics can successfully replicate this function in the cases of the neutral species xylose and pyridine in aqueous solution. ICNCI functions can also be obtained by the addition of a cosolute (such as adding GdmCl or Gdm 2SO4 to pyridine solutions). In that case it is found that molecular dynamics can replicate the ICNCI function for the addition of GdmCl to pyridine, but fails to successfully replicate the same function for the addition of Gdm2SO4. This result implies that the interaction of pyridine with guanidinium sulfate is over-estimated in these MD simulations, and is of significant importance to the use of molecular dynamics simulations to elucidate an atomic level understanding of the Hofmeister series. © 2013 The Royal Society of Chemistry.
Aurelio G.,CONICET |
Curiale J.,CONICET |
Curiale J.,National University of Cuyo |
Bardelli F.,CNRS Institute of Earth Sciences |
And 5 more authors.
Journal of Applied Physics | Year: 2015
Cationic substitutions in the novel magnetoelectric compound CaBaCo4O7 lead to profound changes in its magnetic and electric behaviors. In this work, we present a structural study of the isovalent substitution Sr-for-Ca in CaBaCo4O7. X-ray diffraction, as well as neutron powder diffraction experiments, are reported for a series of samples Ca1- xSrxBaCo4O7 with 0 ≤ x ≤ 0.10. Special emphasis is given to the identification of the substitution site, as Sr has also been reported to substitute for Ba in this crystal structure. The solubility limit for Sr at the Ca site is shown to be at x ≃ 0.08. The variation of lattice constants with Sr-doping firmly supports the Sr-for-Ca substitution. Rietveld refinements of the Sr-substituted samples are presented, and used as starting point to analyse the local structure around Sr by means of X-ray absorption spectroscopy at the Sr K-edge. Both the near-edge absorption and the extended absorption fine-structure confirm the substitution of Sr for Ca, giving definite support to the proposed nominal formula. In addition, macroscopic magnetization measurements are presented which reveal the striking effects of Sr-substitution over the magnetic landscape of this puzzling compound. © 2015 AIP Publishing LLC.
Mason P.E.,Cornell University |
Neilson G.W.,University of Bristol |
Dempsey C.E.,University of Bristol |
Price D.L.,CNRS Center for Research on Divided Matter |
And 2 more authors.
Journal of Physical Chemistry B | Year: 2010
Neutron diffraction with isotopic substitution (NDIS) experiments have been used to examine the structuring of aqueous solutions of pyridine. A new method is described for extracting the structure factors relating to intermolecular correlations from neutron scattering experiments on liquid solutions of complex molecular species. This approach performs experiments at different concentrations and exploits the intramolecular coordination number concentration invariance (ICNCI) to separate the internal and intermolecular contributions to the total intensities. The ability of this method to deconvolute molecular and intermolecular correlations is tested and demonstrated using simulated neutron scattering results predicted from molecular dynamics simulations of aqueous solutions of the polyatomic solute pyridine in which the inter- and intramolecular terms are known. The method is then implemented using neutron scattering measurements on solutions of pyridine. The results confirm that pyridine shows a significant propensity to aggregate in solution and demonstrate the prospects for the future application of the ICNCI approach to the study of large polyatomic solutes using next-generation neutron sources and detectors. © 2010 American Chemical Society.
Babonneau F.,University Pierre and Marie Curie |
Bonhomme C.,University Pierre and Marie Curie |
Gervais C.,University Pierre and Marie Curie |
Azais T.,University Pierre and Marie Curie |
And 14 more authors.
Actualite Chimique | Year: 2012
This article illustrates how solid state NMR, which is by nature a local spectroscopic technique, is also able to establish dialogs between nuclear spins over distances up to few nanometers. Access to such length scales is possible through one-dimensional and multidimensional experiments that give chemical signatures not only from one unique atom in relation with its environment, but from groups of atoms chemically bonded or spatially close. In that sense, solid state NMR appears as a perfect investigation tool for materials with more and more complex compositions and structures. The selected examples belong to families of materials that have been developed for applications in the fields of energy (glasses for nuclear waste management), health (hybrid materials for controlled release of drugs) and sustainable development (heterogeneous catalysts).
Aoun B.,CNRS Center for Research on Divided Matter |
Aoun B.,Laue Langevin Institute |
Gonzalez M.A.,Laue Langevin Institute |
Ollivier J.,Laue Langevin Institute |
And 4 more authors.
Journal of Physical Chemistry Letters | Year: 2010
We present results of parallel quasielastic neutron scattering (QENS) experiments and molecular dynamics numerical simulations for the dynamics of a prototype ionic liquid, 1-ethyl-3-methyl-imidazolium bromide. Differences and similarities with those from the crystal phase are also discussed. Both experiment and simulation demonstrate that, in the length and time scales being probed here (fractions of a nm and a few ps), the dynamics are dominated by activated translational diffusion in the liquid phase and reorientations of the ethyl groups in both solid and liquid. © 2010 American Chemical Society.