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DOI: 10.1021/acs.jpcc.7b06685
WoS: 000417671500003
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14 Citations
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Conversion-type electrode materials show extremely interesting performance in terms of capacity, which is however usually associated with bad Coulombic efficiency. The latter is mainly the consequence of the relentless evolution of solid electrolyte interphase (SEI) formed and/or dissolved during conversion/back-conversion reactions on the continuously reshaping active material surface. The thorough comprehension of the dynamic processes occurring during cycling in a working electrochemical cell, such as solvation/desolvation of ionic species and formation/dissolution of the SEI at the electrode/electrolyte interface, is thus of utmost relevance in the study of electrochemical mechanism and performance of conversion-type electrode materials. Operando Fourier transform infrared (FTIR) spectroscopy, one of the methods of choice for the study of such phenomena, was applied to study the dynamic interfacial properties of NiSb2, a representative intermetallic conversion-type electrode material for Li batteries, during cycling in the presence of a commercial electrolyte based on LiPF6 dissolved in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC). Using a specifically developed in situ ATR-IR electrochemical cell, it was possible to correlate the electrochemical processes to the ratio between solvent molecules associated with Li+ ions and free solvent molecules and thus to follow the dynamic evolution of the concentration of lithium in the electrolyte during cycling.

Ref HAL: hal-01658154_v1
Ref Arxiv: 1706.10081
DOI: 10.1209/0295-5075/119/36003
WoS: 000415019400017
Ref. & Cit.: NASA ADS
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14 Citations
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We use a swap Monte Carlo algorithm to numerically prepare bulk glasses with kinetic stability comparable to that of glass films produced experimentally by physical vapor deposition. By melting these systems into the liquid state, we show that some of our glasses retain their amorphous structures longer than 10^5 times the equilibrium structural relaxation time. This exceptional kinetic stability cannot be achieved experimentally for bulk materials. We perform simulations at both constant volume and constant pressure to demonstrate that the density mismatch between the ultrastable glass and the equilibrium liquid accounts for a major part of the observed kinetic stability.

Commentaires: 7 Pages, 6 Figures. Figures 4b) and 5b) updated, revisions to text to improve discussion, missing page numbers added to references, typos corrected. Réf Journal: EPL 119, 36003 (2017)

Ref HAL: hal-01656760_v1
DOI: 10.1063/1.5012271
WoS: 000416842200006
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4 Citations
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.We present a class of simple algorithms that allows to find the reaction path in systems with a complexpotential energy landscape. The approach does not need any knowledge on the product state and doesnot require the calculation of any second derivatives. The underlying idea is to use two nearby points inconfiguration space to locate the path of slowest ascent. By introducing a weak noise term, the algorithmis able to find even low-lying saddle points that are not reachable by means of a slowest ascent path. Sincethe algorithm makes only use of the value of the potential and its gradient, the computational effort to findsaddles is linear in the number of degrees of freedom, if the potential is short-ranged. We test the performanceof the algorithm for two potential energy landscapes. For the M¨uller-Brown surface we find that the algorithmalways finds the correct saddle point. For the modified M¨uller-Brown surface, which has a saddle point thatis not reachable by means of a slowest ascent path, the algorithm is still able to find this saddle point withhigh probability

Ref HAL: hal-01653592_v1
DOI: 10.18869/acadpub.jafm.73.243.27597
WoS: WOS:000413507000030
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This work regards the extension of the Miles’ and Jeffreys’ theories of growth of wind-waves in water of finite depth. It is divided in two major sections. The first one corresponds to the surface water waves in a linear regimes and the second one to the surface water waver considered in a weak nonlinear, dispersive and anti-dissipative regime. In the linear regime, we extend the Miles’ theory of wind wave amplification to finite depth. The dispersion relation provides a wave growth rate depending to depth. A dimensionless water depth parameter depending to depth and a characteristic wind speed, induces a family of curves representing the wave growth as a function of the wave phase velocity and the wind speed. We obtain a good agreementbetween our theoretical results and the data from the Australian Shallow Water Experiment as well as the data from the Lake George experiment. In a weakly nonlinear regime the evolution of wind waves in finitedepth is reduced to an anti-dissipative Korteweg-de Vries-Burgers equation and its solitary wave solution is exhibited. Anti-dissipation phenomenon accelerates the solitary wave and increases its amplitude whichleads to its blow-up and breaking. Blow-up is a nonlinear, dispersive and anti-dissipative phenomenon which occurs in finite time. A consequence of anti-dissipation is that any solitary waves’ adjacent planes of constants phases acquire different velocities and accelerations and ends to breaking which occurs in finite space and in a finite time prior to the blow-up. It worth remarking that the theoretical amplitude growth breaking time are both testable in the usual experimental facilities. At the end, in the context of windforced waves in finite depth, the nonlinear Schr ̈odinger equation is derived and for weak wind inputs, the Akhmediev, Peregrine and Kuznetsov-Ma breather solutions are obtained

Ref HAL: hal-01653311_v1
DOI: 10.1122/1.5000808
WoS: WOS:000414273200030
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4 Citations
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A simple model is introduced to describe the failure mechanisms in soft thermoplastic elastomers. In particular, we address the strong embrittlement with increasing temperature observed in strain rate imposed tensile experiments. This behavior is in sharp contrast to classic thermoplastics and seems to be general for these types of systems, irrespective of their exact chemical nature. We show that a kinetic model describing the supramolecular association of hard blocks in terms of an Eyring rate equation captures the correct stress and temperature dependence of failure strain. We model the material as a transient network, whose failure is associated with the loss of connectivity. The network percolation threshold, a key parameter of the model, is studied with numerical simulations, in order to investigate the interplay between structure, connectivity, and mechanical properties.