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Haigis V.,German Research Center for Geosciences | Salanne M.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Jahn S.,German Research Center for Geosciences
Earth and Planetary Science Letters | Year: 2012

We report lattice thermal conductivities of MgO and MgSiO3 in the perovskite and post-perovskite structures at conditions of the Earth's lower mantle, obtained from equilibrium molecular dynamics simulations. Using an advanced ionic interaction potential, the full conductivity tensor was calculated by means of the Green-Kubo method, and the conductivity of MgSiO3 post-perovskite was found to be significantly anisotropic. The thermal conductivities of all three phases were parameterized as a function of density and temperature. Assuming a Fe-free lower-mantle composition with mole fractions xMgSiO3=0.66 and xMgO=0.34, the conductivity of the two-phase aggregate was calculated along a model geotherm. It was found to vary considerably with depth, rising from 9.5W/(mK) at the top of the lower mantle to 20.5W/(mK) at the top of the thermal boundary layer above the core-mantle boundary. Extrapolation of experimental data suggests that at deep-mantle conditions, the presence of a realistic amount of iron impurities lowers the thermal conductivity of the aggregate by about 50% (Manthilake et al., 2011a). From this result and our thermal conductivity model, we estimate the heat flux across the core-mantle boundary to be 10.8TW for a Fe-bearing MgO/MgSiO3 perovskite aggregate and 10.6TW for a Fe-bearing MgO/MgSiO3 post-perovskite aggregate. © 2012 Elsevier B.V.

Rotenberg B.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Pagonabarraga I.,University of Barcelona
Molecular Physics | Year: 2013

Electrokinetic effects, i.e. the coupled hydrodynamic and electric phenomena which occur near charged interfaces, constitute a challenge to theorists due to the variety of length and time scales involved. We discuss recent advances in the modelling of these phenomena, emphasising the interplay between the molecular specificity and the collective induced flows that emerge. We discuss the complementary simulation methodologies that have been developed either to focus on the molecular aspects of electrokinetics or on their effective properties on larger scales, as well as the proposed hybrid schemes that can incorporate both aspects. We highlight the insights that molecular studies have brought on the nature of interfacial charges and their implications for kinetic phenomena in confined fluids and also discuss advances in a number of relevant contexts. © 2013 Taylor & Francis.

Pagonabarraga I.,University of Barcelona | Rotenberg B.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Frenkel D.,University of Cambridge
Physical Chemistry Chemical Physics | Year: 2010

Electrokinetic phenomena are of great practical importance in fields as diverse as micro-fluidics, colloid science and oil exploration. However, the quantitative prediction of electrokinetic effects was until recently limited to relatively simple geometries that allowed the use of analytical theories. In the past decade, there has been a rapid development in the use of numerical methods that can be used to model electrokinetic phenomena in complex geometries or, more generally, under conditions where the existing analytical approaches fail. The present paper discusses these recent developments, with special emphasis on the advent of coarse-grained models that make it possible to bridge the gap between a purely atomistic and macroscopic descriptions. © 2010 the Owner Societies.

Sulpizi M.,Johannes Gutenberg University Mainz | Salanne M.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems | Sprik M.,University of Cambridge | Gaigeot M.-P.,University of Evry Val dEssonne | Gaigeot M.-P.,Institut Universitaire de France
Journal of Physical Chemistry Letters | Year: 2013

The vibrational sum frequency generation (VSFG) spectrum of the water liquid-vapor (LV) interface is calculated using density functional theory-based molecular dynamics simulations. The real and imaginary parts of the spectrum are in good agreement with the experimental data, and we provide an assignment of the SFG bands according to the dipole orientation of the interfacial water molecules. We use an instantaneous definition of the surface, which is more adapted to the study of interfacial phenomena than the Gibbs dividing surface. By calculating the vibrational (infrared, Raman) properties for interfaces of varying thickness, we show that the bulk spectra signatures appear after a thin layer of 2-3 Å only. We therefore use this value as a criterion for calculating the VSFG spectrum. © 2012 American Chemical Society.

Mauger A.,CNRS Institute of Mineralogy, Materials Physics and Cosmochemistry | Julien C.,CNRS Physical Chemistry of Electrolytes and Interfacial Nanosystems
Ionics | Year: 2014

The research on the electrodes of Li-ion batteries aims to increase the energy density and the power density, improve the calendar and the cycling life, without sacrificing the safety issues. A constant progress through the years has been obtained owing to the surface treatment of the particles, in particular the coating of the particles with a layer that protects the core region from side reactions with the electrolyte, prevents the loss of oxygen, and the dissolution of the metal ions in the electrolyte, or simply improve the conductivity of the powder. The purpose of the present work is to review the different surface modifications that have been tried in the past for the different electrodes that are currently commercialized, or considered as promising, including the three families of positive electrodes (lamellar, spinel, and olivine families) and the three negative electrodes (carbon, Li4Ti5O12, and silicon). The role of the different coats used to improve either the surface conductivity, or the thermal stability, or the structural integrity is discussed. The limits in the efficiency of these different coats are also analyzed along with the understanding of the surface modifications that have been proposed. © 2014 Springer-Verlag Berlin Heidelberg.

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